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llvm-project/mlir/lib/Dialect/SCF/SCF.cpp

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//===- SCF.cpp - Structured Control Flow Operations -----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "mlir/Dialect/SCF/SCF.h"
#include "mlir/Dialect/MemRef/IR/MemRef.h"
#include "mlir/Dialect/StandardOps/IR/Ops.h"
#include "mlir/Dialect/Tensor/IR/Tensor.h"
#include "mlir/IR/BlockAndValueMapping.h"
#include "mlir/IR/PatternMatch.h"
#include "mlir/Support/MathExtras.h"
#include "mlir/Transforms/InliningUtils.h"
using namespace mlir;
using namespace mlir::scf;
//===----------------------------------------------------------------------===//
// SCFDialect Dialect Interfaces
//===----------------------------------------------------------------------===//
namespace {
struct SCFInlinerInterface : public DialectInlinerInterface {
using DialectInlinerInterface::DialectInlinerInterface;
// We don't have any special restrictions on what can be inlined into
// destination regions (e.g. while/conditional bodies). Always allow it.
bool isLegalToInline(Region *dest, Region *src, bool wouldBeCloned,
BlockAndValueMapping &valueMapping) const final {
return true;
}
// Operations in scf dialect are always legal to inline since they are
// pure.
bool isLegalToInline(Operation *, Region *, bool,
BlockAndValueMapping &) const final {
return true;
}
// Handle the given inlined terminator by replacing it with a new operation
// as necessary. Required when the region has only one block.
void handleTerminator(Operation *op,
ArrayRef<Value> valuesToRepl) const final {
auto retValOp = dyn_cast<scf::YieldOp>(op);
if (!retValOp)
return;
for (auto retValue : llvm::zip(valuesToRepl, retValOp.getOperands())) {
std::get<0>(retValue).replaceAllUsesWith(std::get<1>(retValue));
}
}
};
} // end anonymous namespace
//===----------------------------------------------------------------------===//
// SCFDialect
//===----------------------------------------------------------------------===//
void SCFDialect::initialize() {
addOperations<
#define GET_OP_LIST
#include "mlir/Dialect/SCF/SCFOps.cpp.inc"
>();
addInterfaces<SCFInlinerInterface>();
}
/// Default callback for IfOp builders. Inserts a yield without arguments.
void mlir::scf::buildTerminatedBody(OpBuilder &builder, Location loc) {
builder.create<scf::YieldOp>(loc);
}
//===----------------------------------------------------------------------===//
// ExecuteRegionOp
//===----------------------------------------------------------------------===//
///
/// (ssa-id `=`)? `execute_region` `->` function-result-type `{`
/// block+
/// `}`
///
/// Example:
/// scf.execute_region -> i32 {
/// %idx = load %rI[%i] : memref<128xi32>
/// return %idx : i32
/// }
///
static ParseResult parseExecuteRegionOp(OpAsmParser &parser,
OperationState &result) {
if (parser.parseOptionalArrowTypeList(result.types))
return failure();
// Introduce the body region and parse it.
Region *body = result.addRegion();
if (parser.parseRegion(*body, /*arguments=*/{}, /*argTypes=*/{}) ||
parser.parseOptionalAttrDict(result.attributes))
return failure();
return success();
}
static void print(OpAsmPrinter &p, ExecuteRegionOp op) {
p << ExecuteRegionOp::getOperationName();
if (op.getNumResults() > 0)
p << " -> " << op.getResultTypes();
p.printRegion(op.region(),
/*printEntryBlockArgs=*/false,
/*printBlockTerminators=*/true);
p.printOptionalAttrDict(op->getAttrs());
}
static LogicalResult verify(ExecuteRegionOp op) {
if (op.region().empty())
return op.emitOpError("region needs to have at least one block");
if (op.region().front().getNumArguments() > 0)
return op.emitOpError("region cannot have any arguments");
return success();
}
//===----------------------------------------------------------------------===//
// ForOp
//===----------------------------------------------------------------------===//
void ForOp::build(OpBuilder &builder, OperationState &result, Value lb,
Value ub, Value step, ValueRange iterArgs,
BodyBuilderFn bodyBuilder) {
result.addOperands({lb, ub, step});
result.addOperands(iterArgs);
for (Value v : iterArgs)
result.addTypes(v.getType());
Region *bodyRegion = result.addRegion();
bodyRegion->push_back(new Block);
Block &bodyBlock = bodyRegion->front();
bodyBlock.addArgument(builder.getIndexType());
for (Value v : iterArgs)
bodyBlock.addArgument(v.getType());
// Create the default terminator if the builder is not provided and if the
// iteration arguments are not provided. Otherwise, leave this to the caller
// because we don't know which values to return from the loop.
if (iterArgs.empty() && !bodyBuilder) {
ForOp::ensureTerminator(*bodyRegion, builder, result.location);
} else if (bodyBuilder) {
OpBuilder::InsertionGuard guard(builder);
builder.setInsertionPointToStart(&bodyBlock);
bodyBuilder(builder, result.location, bodyBlock.getArgument(0),
bodyBlock.getArguments().drop_front());
}
}
static LogicalResult verify(ForOp op) {
if (auto cst = op.step().getDefiningOp<ConstantIndexOp>())
if (cst.getValue() <= 0)
return op.emitOpError("constant step operand must be positive");
// Check that the body defines as single block argument for the induction
// variable.
auto *body = op.getBody();
if (!body->getArgument(0).getType().isIndex())
return op.emitOpError(
"expected body first argument to be an index argument for "
"the induction variable");
auto opNumResults = op.getNumResults();
if (opNumResults == 0)
return success();
// If ForOp defines values, check that the number and types of
// the defined values match ForOp initial iter operands and backedge
// basic block arguments.
if (op.getNumIterOperands() != opNumResults)
return op.emitOpError(
"mismatch in number of loop-carried values and defined values");
if (op.getNumRegionIterArgs() != opNumResults)
return op.emitOpError(
"mismatch in number of basic block args and defined values");
auto iterOperands = op.getIterOperands();
auto iterArgs = op.getRegionIterArgs();
auto opResults = op.getResults();
unsigned i = 0;
for (auto e : llvm::zip(iterOperands, iterArgs, opResults)) {
if (std::get<0>(e).getType() != std::get<2>(e).getType())
return op.emitOpError() << "types mismatch between " << i
<< "th iter operand and defined value";
if (std::get<1>(e).getType() != std::get<2>(e).getType())
return op.emitOpError() << "types mismatch between " << i
<< "th iter region arg and defined value";
i++;
}
return RegionBranchOpInterface::verifyTypes(op);
}
/// Prints the initialization list in the form of
/// <prefix>(%inner = %outer, %inner2 = %outer2, <...>)
/// where 'inner' values are assumed to be region arguments and 'outer' values
/// are regular SSA values.
static void printInitializationList(OpAsmPrinter &p,
Block::BlockArgListType blocksArgs,
ValueRange initializers,
StringRef prefix = "") {
assert(blocksArgs.size() == initializers.size() &&
"expected same length of arguments and initializers");
if (initializers.empty())
return;
p << prefix << '(';
llvm::interleaveComma(llvm::zip(blocksArgs, initializers), p, [&](auto it) {
p << std::get<0>(it) << " = " << std::get<1>(it);
});
p << ")";
}
static void print(OpAsmPrinter &p, ForOp op) {
p << op.getOperationName() << " " << op.getInductionVar() << " = "
<< op.lowerBound() << " to " << op.upperBound() << " step " << op.step();
printInitializationList(p, op.getRegionIterArgs(), op.getIterOperands(),
" iter_args");
if (!op.getIterOperands().empty())
p << " -> (" << op.getIterOperands().getTypes() << ')';
p.printRegion(op.region(),
/*printEntryBlockArgs=*/false,
/*printBlockTerminators=*/op.hasIterOperands());
p.printOptionalAttrDict(op->getAttrs());
}
static ParseResult parseForOp(OpAsmParser &parser, OperationState &result) {
auto &builder = parser.getBuilder();
OpAsmParser::OperandType inductionVariable, lb, ub, step;
// Parse the induction variable followed by '='.
if (parser.parseRegionArgument(inductionVariable) || parser.parseEqual())
return failure();
// Parse loop bounds.
Type indexType = builder.getIndexType();
if (parser.parseOperand(lb) ||
parser.resolveOperand(lb, indexType, result.operands) ||
parser.parseKeyword("to") || parser.parseOperand(ub) ||
parser.resolveOperand(ub, indexType, result.operands) ||
parser.parseKeyword("step") || parser.parseOperand(step) ||
parser.resolveOperand(step, indexType, result.operands))
return failure();
// Parse the optional initial iteration arguments.
SmallVector<OpAsmParser::OperandType, 4> regionArgs, operands;
SmallVector<Type, 4> argTypes;
regionArgs.push_back(inductionVariable);
if (succeeded(parser.parseOptionalKeyword("iter_args"))) {
// Parse assignment list and results type list.
if (parser.parseAssignmentList(regionArgs, operands) ||
parser.parseArrowTypeList(result.types))
return failure();
// Resolve input operands.
for (auto operandType : llvm::zip(operands, result.types))
if (parser.resolveOperand(std::get<0>(operandType),
std::get<1>(operandType), result.operands))
return failure();
}
// Induction variable.
argTypes.push_back(indexType);
// Loop carried variables
argTypes.append(result.types.begin(), result.types.end());
// Parse the body region.
Region *body = result.addRegion();
if (regionArgs.size() != argTypes.size())
return parser.emitError(
parser.getNameLoc(),
"mismatch in number of loop-carried values and defined values");
if (parser.parseRegion(*body, regionArgs, argTypes))
return failure();
ForOp::ensureTerminator(*body, builder, result.location);
// Parse the optional attribute list.
if (parser.parseOptionalAttrDict(result.attributes))
return failure();
return success();
}
Region &ForOp::getLoopBody() { return region(); }
bool ForOp::isDefinedOutsideOfLoop(Value value) {
return !region().isAncestor(value.getParentRegion());
}
LogicalResult ForOp::moveOutOfLoop(ArrayRef<Operation *> ops) {
for (auto *op : ops)
op->moveBefore(*this);
return success();
}
ForOp mlir::scf::getForInductionVarOwner(Value val) {
auto ivArg = val.dyn_cast<BlockArgument>();
if (!ivArg)
return ForOp();
assert(ivArg.getOwner() && "unlinked block argument");
auto *containingOp = ivArg.getOwner()->getParentOp();
return dyn_cast_or_null<ForOp>(containingOp);
}
/// Return operands used when entering the region at 'index'. These operands
/// correspond to the loop iterator operands, i.e., those excluding the
/// induction variable. LoopOp only has one region, so 0 is the only valid value
/// for `index`.
OperandRange ForOp::getSuccessorEntryOperands(unsigned index) {
assert(index == 0 && "invalid region index");
// The initial operands map to the loop arguments after the induction
// variable.
return initArgs();
}
/// Given the region at `index`, or the parent operation if `index` is None,
/// return the successor regions. These are the regions that may be selected
/// during the flow of control. `operands` is a set of optional attributes that
/// correspond to a constant value for each operand, or null if that operand is
/// not a constant.
void ForOp::getSuccessorRegions(Optional<unsigned> index,
ArrayRef<Attribute> operands,
SmallVectorImpl<RegionSuccessor> &regions) {
// If the predecessor is the ForOp, branch into the body using the iterator
// arguments.
if (!index.hasValue()) {
regions.push_back(RegionSuccessor(&getLoopBody(), getRegionIterArgs()));
return;
}
// Otherwise, the loop may branch back to itself or the parent operation.
assert(index.getValue() == 0 && "expected loop region");
regions.push_back(RegionSuccessor(&getLoopBody(), getRegionIterArgs()));
regions.push_back(RegionSuccessor(getResults()));
}
void ForOp::getNumRegionInvocations(ArrayRef<Attribute> operands,
SmallVectorImpl<int64_t> &countPerRegion) {
assert(countPerRegion.empty());
countPerRegion.resize(1);
auto lb = operands[0].dyn_cast_or_null<IntegerAttr>();
auto ub = operands[1].dyn_cast_or_null<IntegerAttr>();
auto step = operands[2].dyn_cast_or_null<IntegerAttr>();
// Loop bounds are not known statically.
if (!lb || !ub || !step || step.getValue().getSExtValue() == 0) {
countPerRegion[0] = -1;
return;
}
countPerRegion[0] =
ceilDiv(ub.getValue().getSExtValue() - lb.getValue().getSExtValue(),
step.getValue().getSExtValue());
}
LoopNest mlir::scf::buildLoopNest(
OpBuilder &builder, Location loc, ValueRange lbs, ValueRange ubs,
ValueRange steps, ValueRange iterArgs,
function_ref<ValueVector(OpBuilder &, Location, ValueRange, ValueRange)>
bodyBuilder) {
assert(lbs.size() == ubs.size() &&
"expected the same number of lower and upper bounds");
assert(lbs.size() == steps.size() &&
"expected the same number of lower bounds and steps");
// If there are no bounds, call the body-building function and return early.
if (lbs.empty()) {
ValueVector results =
bodyBuilder ? bodyBuilder(builder, loc, ValueRange(), iterArgs)
: ValueVector();
assert(results.size() == iterArgs.size() &&
"loop nest body must return as many values as loop has iteration "
"arguments");
return LoopNest();
}
// First, create the loop structure iteratively using the body-builder
// callback of `ForOp::build`. Do not create `YieldOp`s yet.
OpBuilder::InsertionGuard guard(builder);
SmallVector<scf::ForOp, 4> loops;
SmallVector<Value, 4> ivs;
loops.reserve(lbs.size());
ivs.reserve(lbs.size());
ValueRange currentIterArgs = iterArgs;
Location currentLoc = loc;
for (unsigned i = 0, e = lbs.size(); i < e; ++i) {
auto loop = builder.create<scf::ForOp>(
currentLoc, lbs[i], ubs[i], steps[i], currentIterArgs,
[&](OpBuilder &nestedBuilder, Location nestedLoc, Value iv,
ValueRange args) {
ivs.push_back(iv);
// It is safe to store ValueRange args because it points to block
// arguments of a loop operation that we also own.
currentIterArgs = args;
currentLoc = nestedLoc;
});
// Set the builder to point to the body of the newly created loop. We don't
// do this in the callback because the builder is reset when the callback
// returns.
builder.setInsertionPointToStart(loop.getBody());
loops.push_back(loop);
}
// For all loops but the innermost, yield the results of the nested loop.
for (unsigned i = 0, e = loops.size() - 1; i < e; ++i) {
builder.setInsertionPointToEnd(loops[i].getBody());
builder.create<scf::YieldOp>(loc, loops[i + 1].getResults());
}
// In the body of the innermost loop, call the body building function if any
// and yield its results.
builder.setInsertionPointToStart(loops.back().getBody());
ValueVector results = bodyBuilder
? bodyBuilder(builder, currentLoc, ivs,
loops.back().getRegionIterArgs())
: ValueVector();
assert(results.size() == iterArgs.size() &&
"loop nest body must return as many values as loop has iteration "
"arguments");
builder.setInsertionPointToEnd(loops.back().getBody());
builder.create<scf::YieldOp>(loc, results);
// Return the loops.
LoopNest res;
res.loops.assign(loops.begin(), loops.end());
return res;
}
LoopNest mlir::scf::buildLoopNest(
OpBuilder &builder, Location loc, ValueRange lbs, ValueRange ubs,
ValueRange steps,
function_ref<void(OpBuilder &, Location, ValueRange)> bodyBuilder) {
// Delegate to the main function by wrapping the body builder.
return buildLoopNest(builder, loc, lbs, ubs, steps, llvm::None,
[&bodyBuilder](OpBuilder &nestedBuilder,
Location nestedLoc, ValueRange ivs,
ValueRange) -> ValueVector {
if (bodyBuilder)
bodyBuilder(nestedBuilder, nestedLoc, ivs);
return {};
});
}
/// Replaces the given op with the contents of the given single-block region,
/// using the operands of the block terminator to replace operation results.
static void replaceOpWithRegion(PatternRewriter &rewriter, Operation *op,
Region &region, ValueRange blockArgs = {}) {
assert(llvm::hasSingleElement(region) && "expected single-region block");
Block *block = &region.front();
Operation *terminator = block->getTerminator();
ValueRange results = terminator->getOperands();
rewriter.mergeBlockBefore(block, op, blockArgs);
rewriter.replaceOp(op, results);
rewriter.eraseOp(terminator);
}
namespace {
// Fold away ForOp iter arguments when:
// 1) The op yields the iter arguments.
// 2) The iter arguments have no use and the corresponding outer region
// iterators (inputs) are yielded.
// 3) The iter arguments have no use and the corresponding (operation) results
// have no use.
//
// These arguments must be defined outside of
// the ForOp region and can just be forwarded after simplifying the op inits,
// yields and returns.
//
// The implementation uses `mergeBlockBefore` to steal the content of the
// original ForOp and avoid cloning.
struct ForOpIterArgsFolder : public OpRewritePattern<scf::ForOp> {
using OpRewritePattern<scf::ForOp>::OpRewritePattern;
LogicalResult matchAndRewrite(scf::ForOp forOp,
PatternRewriter &rewriter) const final {
bool canonicalize = false;
Block &block = forOp.region().front();
auto yieldOp = cast<scf::YieldOp>(block.getTerminator());
// An internal flat vector of block transfer
// arguments `newBlockTransferArgs` keeps the 1-1 mapping of original to
// transformed block argument mappings. This plays the role of a
// BlockAndValueMapping for the particular use case of calling into
// `mergeBlockBefore`.
SmallVector<bool, 4> keepMask;
keepMask.reserve(yieldOp.getNumOperands());
SmallVector<Value, 4> newBlockTransferArgs, newIterArgs, newYieldValues,
newResultValues;
newBlockTransferArgs.reserve(1 + forOp.getNumIterOperands());
newBlockTransferArgs.push_back(Value()); // iv placeholder with null value
newIterArgs.reserve(forOp.getNumIterOperands());
newYieldValues.reserve(yieldOp.getNumOperands());
newResultValues.reserve(forOp.getNumResults());
for (auto it : llvm::zip(forOp.getIterOperands(), // iter from outside
forOp.getRegionIterArgs(), // iter inside region
forOp.getResults(), // op results
yieldOp.getOperands() // iter yield
)) {
// Forwarded is `true` when:
// 1) The region `iter` argument is yielded.
// 2) The region `iter` argument has no use, and the corresponding iter
// operand (input) is yielded.
// 3) The region `iter` argument has no use, and the corresponding op
// result has no use.
bool forwarded = ((std::get<1>(it) == std::get<3>(it)) ||
(std::get<1>(it).use_empty() &&
(std::get<0>(it) == std::get<3>(it) ||
std::get<2>(it).use_empty())));
keepMask.push_back(!forwarded);
canonicalize |= forwarded;
if (forwarded) {
newBlockTransferArgs.push_back(std::get<0>(it));
newResultValues.push_back(std::get<0>(it));
continue;
}
newIterArgs.push_back(std::get<0>(it));
newYieldValues.push_back(std::get<3>(it));
newBlockTransferArgs.push_back(Value()); // placeholder with null value
newResultValues.push_back(Value()); // placeholder with null value
}
if (!canonicalize)
return failure();
scf::ForOp newForOp = rewriter.create<scf::ForOp>(
forOp.getLoc(), forOp.lowerBound(), forOp.upperBound(), forOp.step(),
newIterArgs);
Block &newBlock = newForOp.region().front();
// Replace the null placeholders with newly constructed values.
newBlockTransferArgs[0] = newBlock.getArgument(0); // iv
for (unsigned idx = 0, collapsedIdx = 0, e = newResultValues.size();
idx != e; ++idx) {
Value &blockTransferArg = newBlockTransferArgs[1 + idx];
Value &newResultVal = newResultValues[idx];
assert((blockTransferArg && newResultVal) ||
(!blockTransferArg && !newResultVal));
if (!blockTransferArg) {
blockTransferArg = newForOp.getRegionIterArgs()[collapsedIdx];
newResultVal = newForOp.getResult(collapsedIdx++);
}
}
Block &oldBlock = forOp.region().front();
assert(oldBlock.getNumArguments() == newBlockTransferArgs.size() &&
"unexpected argument size mismatch");
// No results case: the scf::ForOp builder already created a zero
// result terminator. Merge before this terminator and just get rid of the
// original terminator that has been merged in.
if (newIterArgs.empty()) {
auto newYieldOp = cast<scf::YieldOp>(newBlock.getTerminator());
rewriter.mergeBlockBefore(&oldBlock, newYieldOp, newBlockTransferArgs);
rewriter.eraseOp(newBlock.getTerminator()->getPrevNode());
rewriter.replaceOp(forOp, newResultValues);
return success();
}
// No terminator case: merge and rewrite the merged terminator.
auto cloneFilteredTerminator = [&](scf::YieldOp mergedTerminator) {
OpBuilder::InsertionGuard g(rewriter);
rewriter.setInsertionPoint(mergedTerminator);
SmallVector<Value, 4> filteredOperands;
filteredOperands.reserve(newResultValues.size());
for (unsigned idx = 0, e = keepMask.size(); idx < e; ++idx)
if (keepMask[idx])
filteredOperands.push_back(mergedTerminator.getOperand(idx));
rewriter.create<scf::YieldOp>(mergedTerminator.getLoc(),
filteredOperands);
};
rewriter.mergeBlocks(&oldBlock, &newBlock, newBlockTransferArgs);
auto mergedYieldOp = cast<scf::YieldOp>(newBlock.getTerminator());
cloneFilteredTerminator(mergedYieldOp);
rewriter.eraseOp(mergedYieldOp);
rewriter.replaceOp(forOp, newResultValues);
return success();
}
};
/// Rewriting pattern that erases loops that are known not to iterate and
/// replaces single-iteration loops with their bodies.
struct SimplifyTrivialLoops : public OpRewritePattern<ForOp> {
using OpRewritePattern<ForOp>::OpRewritePattern;
LogicalResult matchAndRewrite(ForOp op,
PatternRewriter &rewriter) const override {
// If the upper bound is the same as the lower bound, the loop does not
// iterate, just remove it.
if (op.lowerBound() == op.upperBound()) {
rewriter.replaceOp(op, op.getIterOperands());
return success();
}
auto lb = op.lowerBound().getDefiningOp<ConstantOp>();
auto ub = op.upperBound().getDefiningOp<ConstantOp>();
if (!lb || !ub)
return failure();
// If the loop is known to have 0 iterations, remove it.
llvm::APInt lbValue = lb.getValue().cast<IntegerAttr>().getValue();
llvm::APInt ubValue = ub.getValue().cast<IntegerAttr>().getValue();
if (lbValue.sge(ubValue)) {
rewriter.replaceOp(op, op.getIterOperands());
return success();
}
auto step = op.step().getDefiningOp<ConstantOp>();
if (!step)
return failure();
// If the loop is known to have 1 iteration, inline its body and remove the
// loop.
llvm::APInt stepValue = step.getValue().cast<IntegerAttr>().getValue();
if ((lbValue + stepValue).sge(ubValue)) {
SmallVector<Value, 4> blockArgs;
blockArgs.reserve(op.getNumIterOperands() + 1);
blockArgs.push_back(op.lowerBound());
llvm::append_range(blockArgs, op.getIterOperands());
replaceOpWithRegion(rewriter, op, op.getLoopBody(), blockArgs);
return success();
}
return failure();
}
};
/// Perform a replacement of one iter OpOperand of an scf.for to the
/// `replacement` value which is expected to be the source of a tensor.cast.
/// tensor.cast ops are inserted inside the block to account for the type cast.
static ForOp replaceTensorCastForOpIterArg(PatternRewriter &rewriter,
OpOperand &operand,
Value replacement) {
Type oldType = operand.get().getType(), newType = replacement.getType();
assert(oldType.isa<RankedTensorType>() && newType.isa<RankedTensorType>() &&
"expected ranked tensor types");
// 1. Create new iter operands, exactly 1 is replaced.
ForOp forOp = cast<ForOp>(operand.getOwner());
assert(operand.getOperandNumber() >= forOp.getNumControlOperands() &&
"expected an iter OpOperand");
if (operand.get().getType() == replacement.getType())
return forOp;
SmallVector<Value> newIterOperands;
for (OpOperand &opOperand : forOp.getIterOpOperands()) {
if (opOperand.getOperandNumber() == operand.getOperandNumber()) {
newIterOperands.push_back(replacement);
continue;
}
newIterOperands.push_back(opOperand.get());
}
// 2. Create the new forOp shell.
scf::ForOp newForOp = rewriter.create<scf::ForOp>(
forOp.getLoc(), forOp.lowerBound(), forOp.upperBound(), forOp.step(),
newIterOperands);
Block &newBlock = newForOp.region().front();
SmallVector<Value, 4> newBlockTransferArgs(newBlock.getArguments().begin(),
newBlock.getArguments().end());
// 3. Inject an incoming cast op at the beginning of the block for the bbArg
// corresponding to the `replacement` value.
OpBuilder::InsertionGuard g(rewriter);
rewriter.setInsertionPoint(&newBlock, newBlock.begin());
BlockArgument newRegionIterArg = newForOp.getRegionIterArgForOpOperand(
newForOp->getOpOperand(operand.getOperandNumber()));
Value castIn = rewriter.create<tensor::CastOp>(newForOp.getLoc(), oldType,
newRegionIterArg);
newBlockTransferArgs[newRegionIterArg.getArgNumber()] = castIn;
// 4. Steal the old block ops, mapping to the newBlockTransferArgs.
Block &oldBlock = forOp.region().front();
rewriter.mergeBlocks(&oldBlock, &newBlock, newBlockTransferArgs);
// 5. Inject an outgoing cast op at the end of the block and yield it instead.
auto clonedYieldOp = cast<scf::YieldOp>(newBlock.getTerminator());
rewriter.setInsertionPoint(clonedYieldOp);
unsigned yieldIdx =
newRegionIterArg.getArgNumber() - forOp.getNumInductionVars();
Value castOut = rewriter.create<tensor::CastOp>(
newForOp.getLoc(), newType, clonedYieldOp.getOperand(yieldIdx));
SmallVector<Value> newYieldOperands = clonedYieldOp.getOperands();
newYieldOperands[yieldIdx] = castOut;
rewriter.create<scf::YieldOp>(newForOp.getLoc(), newYieldOperands);
rewriter.eraseOp(clonedYieldOp);
// 6. Inject an outgoing cast op after the forOp.
rewriter.setInsertionPointAfter(newForOp);
SmallVector<Value> newResults = newForOp.getResults();
newResults[yieldIdx] = rewriter.create<tensor::CastOp>(
newForOp.getLoc(), oldType, newResults[yieldIdx]);
return newForOp;
}
/// Fold scf.for iter_arg/result pairs that go through incoming/ougoing
/// a tensor.cast op pair so as to pull the tensor.cast inside the scf.for:
///
/// ```
/// %0 = tensor.cast %t0 : tensor<32x1024xf32> to tensor<?x?xf32>
/// %1 = scf.for %i = %c0 to %c1024 step %c32 iter_args(%iter_t0 = %0)
/// -> (tensor<?x?xf32>) {
/// %2 = call @do(%iter_t0) : (tensor<?x?xf32>) -> tensor<?x?xf32>
/// scf.yield %2 : tensor<?x?xf32>
/// }
/// %2 = tensor.cast %1 : tensor<?x?xf32> to tensor<32x1024xf32>
/// use_of(%2)
/// ```
///
/// folds into:
///
/// ```
/// %0 = scf.for %arg2 = %c0 to %c1024 step %c32 iter_args(%arg3 = %arg0)
/// -> (tensor<32x1024xf32>) {
/// %2 = tensor.cast %arg3 : tensor<32x1024xf32> to tensor<?x?xf32>
/// %3 = call @do(%2) : (tensor<?x?xf32>) -> tensor<?x?xf32>
/// %4 = tensor.cast %3 : tensor<?x?xf32> to tensor<32x1024xf32>
/// scf.yield %4 : tensor<32x1024xf32>
/// }
/// use_of(%0)
/// ```
struct ForOpTensorCastFolder : public OpRewritePattern<ForOp> {
using OpRewritePattern<ForOp>::OpRewritePattern;
LogicalResult matchAndRewrite(ForOp op,
PatternRewriter &rewriter) const override {
for (auto it : llvm::zip(op.getIterOpOperands(), op.getResults())) {
OpOperand &iterOpOperand = std::get<0>(it);
auto incomingCast = iterOpOperand.get().getDefiningOp<tensor::CastOp>();
if (!incomingCast)
continue;
if (!std::get<1>(it).hasOneUse())
continue;
auto outgoingCastOp =
dyn_cast<tensor::CastOp>(*std::get<1>(it).user_begin());
if (!outgoingCastOp)
continue;
// Must be a tensor.cast op pair with matching types.
if (outgoingCastOp.getResult().getType() !=
incomingCast.source().getType())
continue;
// Create a new ForOp with that iter operand replaced.
auto newForOp = replaceTensorCastForOpIterArg(rewriter, iterOpOperand,
incomingCast.source());
// Insert outgoing cast and use it to replace the corresponding result.
rewriter.setInsertionPointAfter(newForOp);
SmallVector<Value> replacements = newForOp.getResults();
unsigned returnIdx =
iterOpOperand.getOperandNumber() - op.getNumControlOperands();
replacements[returnIdx] = rewriter.create<tensor::CastOp>(
op.getLoc(), incomingCast.dest().getType(), replacements[returnIdx]);
rewriter.replaceOp(op, replacements);
return success();
}
return failure();
}
};
/// Canonicalize the iter_args of an scf::ForOp that involve a tensor_load and
/// for which only the last loop iteration is actually visible outside of the
/// loop. The canonicalization looks for a pattern such as:
/// ```
/// %t0 = ... : tensor_type
/// %0 = scf.for ... iter_args(%bb0 : %t0) -> (tensor_type) {
/// ...
/// // %m is either buffer_cast(%bb00) or defined above the loop
/// %m... : memref_type
/// ... // uses of %m with potential inplace updates
/// %new_tensor = tensor_load %m : memref_type
/// ...
/// scf.yield %new_tensor : tensor_type
/// }
/// ```
///
/// `%bb0` may have either 0 or 1 use. If it has 1 use it must be exactly a
/// `%m = buffer_cast %bb0` op that feeds into the yielded `tensor_load`
/// op.
///
/// If no aliasing write to the memref `%m`, from which `%new_tensor`is loaded,
/// occurs between tensor_load and yield then the value %0 visible outside of
/// the loop is the last `tensor_load` produced in the loop.
///
/// For now, we approximate the absence of aliasing by only supporting the case
/// when the tensor_load is the operation immediately preceding the yield.
///
/// The canonicalization rewrites the pattern as:
/// ```
/// // %m is either a buffer_cast or defined above
/// %m... : memref_type
/// scf.for ... iter_args(%bb0 : %t0) -> (tensor_type) {
/// ... // uses of %m with potential inplace updates
/// scf.yield %bb0: tensor_type
/// }
/// %0 = tensor_load %m : memref_type
/// ```
///
/// A later bbArg canonicalization will further rewrite as:
/// ```
/// // %m is either a buffer_cast or defined above
/// %m... : memref_type
/// scf.for ... { // no iter_args
/// ... // uses of %m with potential inplace updates
/// }
/// %0 = tensor_load %m : memref_type
/// ```
struct LastTensorLoadCanonicalization : public OpRewritePattern<ForOp> {
using OpRewritePattern<ForOp>::OpRewritePattern;
LogicalResult matchAndRewrite(ForOp forOp,
PatternRewriter &rewriter) const override {
assert(std::next(forOp.region().begin()) == forOp.region().end() &&
"unexpected multiple blocks");
Location loc = forOp.getLoc();
DenseMap<Value, Value> replacements;
for (BlockArgument bbArg : forOp.getRegionIterArgs()) {
unsigned idx = bbArg.getArgNumber() - /*numIv=*/1;
auto yieldOp = cast<scf::YieldOp>(forOp.region().front().getTerminator());
Value yieldVal = yieldOp->getOperand(idx);
auto tensorLoadOp = yieldVal.getDefiningOp<memref::TensorLoadOp>();
bool isTensor = bbArg.getType().isa<TensorType>();
memref::BufferCastOp bufferCastOp;
// Either bbArg has no use or it has a single buffer_cast use.
if (bbArg.hasOneUse())
bufferCastOp =
dyn_cast<memref::BufferCastOp>(*bbArg.getUsers().begin());
if (!isTensor || !tensorLoadOp || (!bbArg.use_empty() && !bufferCastOp))
continue;
// If bufferCastOp is present, it must feed into the `tensorLoadOp`.
if (bufferCastOp && tensorLoadOp.memref() != bufferCastOp)
continue;
// TODO: Any aliasing write of tensorLoadOp.memref() nested under `forOp`
// must be before `tensorLoadOp` in the block so that the lastWrite
// property is not subject to additional side-effects.
// For now, we only support the case when tensorLoadOp appears immediately
// before the terminator.
if (tensorLoadOp->getNextNode() != yieldOp)
continue;
// Clone the optional bufferCastOp before forOp.
if (bufferCastOp) {
rewriter.setInsertionPoint(forOp);
rewriter.replaceOpWithNewOp<memref::BufferCastOp>(
bufferCastOp, bufferCastOp.memref().getType(),
bufferCastOp.tensor());
}
// Clone the tensorLoad after forOp.
rewriter.setInsertionPointAfter(forOp);
Value newTensorLoad =
rewriter.create<memref::TensorLoadOp>(loc, tensorLoadOp.memref());
Value forOpResult = forOp.getResult(bbArg.getArgNumber() - /*iv=*/1);
replacements.insert(std::make_pair(forOpResult, newTensorLoad));
// Make the terminator just yield the bbArg, the old tensorLoadOp + the
// old bbArg (that is now directly yielded) will canonicalize away.
rewriter.startRootUpdate(yieldOp);
yieldOp.setOperand(idx, bbArg);
rewriter.finalizeRootUpdate(yieldOp);
}
if (replacements.empty())
return failure();
// We want to replace a subset of the results of `forOp`. rewriter.replaceOp
// replaces the whole op and erase it unconditionally. This is wrong for
// `forOp` as it generally contains ops with side effects.
// Instead, use `rewriter.replaceOpWithIf`.
SmallVector<Value> newResults;
newResults.reserve(forOp.getNumResults());
for (Value v : forOp.getResults()) {
auto it = replacements.find(v);
newResults.push_back((it != replacements.end()) ? it->second : v);
}
unsigned idx = 0;
rewriter.replaceOpWithIf(forOp, newResults, [&](OpOperand &op) {
return op.get() != newResults[idx++];
});
return success();
}
};
} // namespace
void ForOp::getCanonicalizationPatterns(RewritePatternSet &results,
MLIRContext *context) {
results.add<ForOpIterArgsFolder, SimplifyTrivialLoops,
LastTensorLoadCanonicalization, ForOpTensorCastFolder>(context);
}
//===----------------------------------------------------------------------===//
// IfOp
//===----------------------------------------------------------------------===//
void IfOp::build(OpBuilder &builder, OperationState &result, Value cond,
bool withElseRegion) {
build(builder, result, /*resultTypes=*/llvm::None, cond, withElseRegion);
}
void IfOp::build(OpBuilder &builder, OperationState &result,
TypeRange resultTypes, Value cond, bool withElseRegion) {
auto addTerminator = [&](OpBuilder &nested, Location loc) {
if (resultTypes.empty())
IfOp::ensureTerminator(*nested.getInsertionBlock()->getParent(), nested,
loc);
};
build(builder, result, resultTypes, cond, addTerminator,
withElseRegion ? addTerminator
: function_ref<void(OpBuilder &, Location)>());
}
void IfOp::build(OpBuilder &builder, OperationState &result,
TypeRange resultTypes, Value cond,
function_ref<void(OpBuilder &, Location)> thenBuilder,
function_ref<void(OpBuilder &, Location)> elseBuilder) {
assert(thenBuilder && "the builder callback for 'then' must be present");
result.addOperands(cond);
result.addTypes(resultTypes);
OpBuilder::InsertionGuard guard(builder);
Region *thenRegion = result.addRegion();
builder.createBlock(thenRegion);
thenBuilder(builder, result.location);
Region *elseRegion = result.addRegion();
if (!elseBuilder)
return;
builder.createBlock(elseRegion);
elseBuilder(builder, result.location);
}
void IfOp::build(OpBuilder &builder, OperationState &result, Value cond,
function_ref<void(OpBuilder &, Location)> thenBuilder,
function_ref<void(OpBuilder &, Location)> elseBuilder) {
build(builder, result, TypeRange(), cond, thenBuilder, elseBuilder);
}
static LogicalResult verify(IfOp op) {
if (op.getNumResults() != 0 && op.elseRegion().empty())
return op.emitOpError("must have an else block if defining values");
return RegionBranchOpInterface::verifyTypes(op);
}
static ParseResult parseIfOp(OpAsmParser &parser, OperationState &result) {
// Create the regions for 'then'.
result.regions.reserve(2);
Region *thenRegion = result.addRegion();
Region *elseRegion = result.addRegion();
auto &builder = parser.getBuilder();
OpAsmParser::OperandType cond;
Type i1Type = builder.getIntegerType(1);
if (parser.parseOperand(cond) ||
parser.resolveOperand(cond, i1Type, result.operands))
return failure();
// Parse optional results type list.
if (parser.parseOptionalArrowTypeList(result.types))
return failure();
// Parse the 'then' region.
if (parser.parseRegion(*thenRegion, /*arguments=*/{}, /*argTypes=*/{}))
return failure();
IfOp::ensureTerminator(*thenRegion, parser.getBuilder(), result.location);
// If we find an 'else' keyword then parse the 'else' region.
if (!parser.parseOptionalKeyword("else")) {
if (parser.parseRegion(*elseRegion, /*arguments=*/{}, /*argTypes=*/{}))
return failure();
IfOp::ensureTerminator(*elseRegion, parser.getBuilder(), result.location);
}
// Parse the optional attribute list.
if (parser.parseOptionalAttrDict(result.attributes))
return failure();
return success();
}
static void print(OpAsmPrinter &p, IfOp op) {
bool printBlockTerminators = false;
p << IfOp::getOperationName() << " " << op.condition();
if (!op.results().empty()) {
p << " -> (" << op.getResultTypes() << ")";
// Print yield explicitly if the op defines values.
printBlockTerminators = true;
}
p.printRegion(op.thenRegion(),
/*printEntryBlockArgs=*/false,
/*printBlockTerminators=*/printBlockTerminators);
// Print the 'else' regions if it exists and has a block.
auto &elseRegion = op.elseRegion();
if (!elseRegion.empty()) {
p << " else";
p.printRegion(elseRegion,
/*printEntryBlockArgs=*/false,
/*printBlockTerminators=*/printBlockTerminators);
}
p.printOptionalAttrDict(op->getAttrs());
}
/// Given the region at `index`, or the parent operation if `index` is None,
/// return the successor regions. These are the regions that may be selected
/// during the flow of control. `operands` is a set of optional attributes that
/// correspond to a constant value for each operand, or null if that operand is
/// not a constant.
void IfOp::getSuccessorRegions(Optional<unsigned> index,
ArrayRef<Attribute> operands,
SmallVectorImpl<RegionSuccessor> &regions) {
// The `then` and the `else` region branch back to the parent operation.
if (index.hasValue()) {
regions.push_back(RegionSuccessor(getResults()));
return;
}
// Don't consider the else region if it is empty.
Region *elseRegion = &this->elseRegion();
if (elseRegion->empty())
elseRegion = nullptr;
// Otherwise, the successor is dependent on the condition.
bool condition;
if (auto condAttr = operands.front().dyn_cast_or_null<IntegerAttr>()) {
condition = condAttr.getValue().isOneValue();
} else {
// If the condition isn't constant, both regions may be executed.
regions.push_back(RegionSuccessor(&thenRegion()));
// If the else region does not exist, it is not a viable successor.
if (elseRegion)
regions.push_back(RegionSuccessor(elseRegion));
return;
}
// Add the successor regions using the condition.
regions.push_back(RegionSuccessor(condition ? &thenRegion() : elseRegion));
}
namespace {
// Pattern to remove unused IfOp results.
struct RemoveUnusedResults : public OpRewritePattern<IfOp> {
using OpRewritePattern<IfOp>::OpRewritePattern;
void transferBody(Block *source, Block *dest, ArrayRef<OpResult> usedResults,
PatternRewriter &rewriter) const {
// Move all operations to the destination block.
rewriter.mergeBlocks(source, dest);
// Replace the yield op by one that returns only the used values.
auto yieldOp = cast<scf::YieldOp>(dest->getTerminator());
SmallVector<Value, 4> usedOperands;
llvm::transform(usedResults, std::back_inserter(usedOperands),
[&](OpResult result) {
return yieldOp.getOperand(result.getResultNumber());
});
rewriter.updateRootInPlace(yieldOp,
[&]() { yieldOp->setOperands(usedOperands); });
}
LogicalResult matchAndRewrite(IfOp op,
PatternRewriter &rewriter) const override {
// Compute the list of used results.
SmallVector<OpResult, 4> usedResults;
llvm::copy_if(op.getResults(), std::back_inserter(usedResults),
[](OpResult result) { return !result.use_empty(); });
// Replace the operation if only a subset of its results have uses.
if (usedResults.size() == op.getNumResults())
return failure();
// Compute the result types of the replacement operation.
SmallVector<Type, 4> newTypes;
llvm::transform(usedResults, std::back_inserter(newTypes),
[](OpResult result) { return result.getType(); });
// Create a replacement operation with empty then and else regions.
auto emptyBuilder = [](OpBuilder &, Location) {};
auto newOp = rewriter.create<IfOp>(op.getLoc(), newTypes, op.condition(),
emptyBuilder, emptyBuilder);
// Move the bodies and replace the terminators (note there is a then and
// an else region since the operation returns results).
transferBody(op.getBody(0), newOp.getBody(0), usedResults, rewriter);
transferBody(op.getBody(1), newOp.getBody(1), usedResults, rewriter);
// Replace the operation by the new one.
SmallVector<Value, 4> repResults(op.getNumResults());
for (auto en : llvm::enumerate(usedResults))
repResults[en.value().getResultNumber()] = newOp.getResult(en.index());
rewriter.replaceOp(op, repResults);
return success();
}
};
struct RemoveStaticCondition : public OpRewritePattern<IfOp> {
using OpRewritePattern<IfOp>::OpRewritePattern;
LogicalResult matchAndRewrite(IfOp op,
PatternRewriter &rewriter) const override {
auto constant = op.condition().getDefiningOp<ConstantOp>();
if (!constant)
return failure();
if (constant.getValue().cast<BoolAttr>().getValue())
replaceOpWithRegion(rewriter, op, op.thenRegion());
else if (!op.elseRegion().empty())
replaceOpWithRegion(rewriter, op, op.elseRegion());
else
rewriter.eraseOp(op);
return success();
}
};
struct ConvertTrivialIfToSelect : public OpRewritePattern<IfOp> {
using OpRewritePattern<IfOp>::OpRewritePattern;
LogicalResult matchAndRewrite(IfOp op,
PatternRewriter &rewriter) const override {
if (op->getNumResults() == 0)
return failure();
if (!llvm::hasSingleElement(op.thenRegion().front()) ||
!llvm::hasSingleElement(op.elseRegion().front()))
return failure();
auto cond = op.condition();
auto thenYieldArgs =
cast<scf::YieldOp>(op.thenRegion().front().getTerminator())
.getOperands();
auto elseYieldArgs =
cast<scf::YieldOp>(op.elseRegion().front().getTerminator())
.getOperands();
SmallVector<Value> results(op->getNumResults());
assert(thenYieldArgs.size() == results.size());
assert(elseYieldArgs.size() == results.size());
for (auto it : llvm::enumerate(llvm::zip(thenYieldArgs, elseYieldArgs))) {
Value trueVal = std::get<0>(it.value());
Value falseVal = std::get<1>(it.value());
if (trueVal == falseVal)
results[it.index()] = trueVal;
else
results[it.index()] =
rewriter.create<SelectOp>(op.getLoc(), cond, trueVal, falseVal);
}
rewriter.replaceOp(op, results);
return success();
}
};
/// Allow the true region of an if to assume the condition is true
/// and vice versa. For example:
///
/// scf.if %cmp {
/// print(%cmp)
/// }
///
/// becomes
///
/// scf.if %cmp {
/// print(true)
/// }
///
struct ConditionPropagation : public OpRewritePattern<IfOp> {
using OpRewritePattern<IfOp>::OpRewritePattern;
LogicalResult matchAndRewrite(IfOp op,
PatternRewriter &rewriter) const override {
// Early exit if the condition is constant since replacing a constant
// in the body with another constant isn't a simplification.
if (op.condition().getDefiningOp<ConstantOp>())
return failure();
bool changed = false;
mlir::Type i1Ty = rewriter.getI1Type();
// These variables serve to prevent creating duplicate constants
// and hold constant true or false values.
Value constantTrue = nullptr;
Value constantFalse = nullptr;
for (OpOperand &use :
llvm::make_early_inc_range(op.condition().getUses())) {
if (op.thenRegion().isAncestor(use.getOwner()->getParentRegion())) {
changed = true;
if (!constantTrue)
constantTrue = rewriter.create<mlir::ConstantOp>(
op.getLoc(), i1Ty, rewriter.getIntegerAttr(i1Ty, 1));
rewriter.updateRootInPlace(use.getOwner(),
[&]() { use.set(constantTrue); });
} else if (op.elseRegion().isAncestor(
use.getOwner()->getParentRegion())) {
changed = true;
if (!constantFalse)
constantFalse = rewriter.create<mlir::ConstantOp>(
op.getLoc(), i1Ty, rewriter.getIntegerAttr(i1Ty, 0));
rewriter.updateRootInPlace(use.getOwner(),
[&]() { use.set(constantFalse); });
}
}
return success(changed);
}
};
/// Remove any statements from an if that are equivalent to the condition
/// or its negation. For example:
///
/// %res:2 = scf.if %cmp {
/// yield something(), true
/// } else {
/// yield something2(), false
/// }
/// print(%res#1)
///
/// becomes
/// %res = scf.if %cmp {
/// yield something()
/// } else {
/// yield something2()
/// }
/// print(%cmp)
///
/// Additionally if both branches yield the same value, replace all uses
/// of the result with the yielded value.
///
/// %res:2 = scf.if %cmp {
/// yield something(), %arg1
/// } else {
/// yield something2(), %arg1
/// }
/// print(%res#1)
///
/// becomes
/// %res = scf.if %cmp {
/// yield something()
/// } else {
/// yield something2()
/// }
/// print(%arg1)
///
struct ReplaceIfYieldWithConditionOrValue : public OpRewritePattern<IfOp> {
using OpRewritePattern<IfOp>::OpRewritePattern;
LogicalResult matchAndRewrite(IfOp op,
PatternRewriter &rewriter) const override {
// Early exit if there are no results that could be replaced.
if (op.getNumResults() == 0)
return failure();
auto trueYield = cast<scf::YieldOp>(op.thenRegion().back().getTerminator());
auto falseYield =
cast<scf::YieldOp>(op.elseRegion().back().getTerminator());
rewriter.setInsertionPoint(op->getBlock(),
op.getOperation()->getIterator());
bool changed = false;
Type i1Ty = rewriter.getI1Type();
for (auto tup :
llvm::zip(trueYield.results(), falseYield.results(), op.results())) {
Value trueResult, falseResult, opResult;
std::tie(trueResult, falseResult, opResult) = tup;
if (trueResult == falseResult) {
if (!opResult.use_empty()) {
opResult.replaceAllUsesWith(trueResult);
changed = true;
}
continue;
}
auto trueYield = trueResult.getDefiningOp<ConstantOp>();
if (!trueYield)
continue;
if (!trueYield.getType().isInteger(1))
continue;
auto falseYield = falseResult.getDefiningOp<ConstantOp>();
if (!falseYield)
continue;
bool trueVal = trueYield.getValue().cast<BoolAttr>().getValue();
bool falseVal = falseYield.getValue().cast<BoolAttr>().getValue();
if (!trueVal && falseVal) {
if (!opResult.use_empty()) {
Value notCond = rewriter.create<XOrOp>(
op.getLoc(), op.condition(),
rewriter.create<mlir::ConstantOp>(
op.getLoc(), i1Ty, rewriter.getIntegerAttr(i1Ty, 1)));
opResult.replaceAllUsesWith(notCond);
changed = true;
}
}
if (trueVal && !falseVal) {
if (!opResult.use_empty()) {
opResult.replaceAllUsesWith(op.condition());
changed = true;
}
}
}
return success(changed);
}
};
/// Merge any consecutive scf.if's with the same condition.
///
/// scf.if %cond {
/// firstCodeTrue();...
/// } else {
/// firstCodeFalse();...
/// }
/// %res = scf.if %cond {
/// secondCodeTrue();...
/// } else {
/// secondCodeFalse();...
/// }
///
/// becomes
/// %res = scf.if %cmp {
/// firstCodeTrue();...
/// secondCodeTrue();...
/// } else {
/// firstCodeFalse();...
/// secondCodeFalse();...
/// }
struct CombineIfs : public OpRewritePattern<IfOp> {
using OpRewritePattern<IfOp>::OpRewritePattern;
LogicalResult matchAndRewrite(IfOp nextIf,
PatternRewriter &rewriter) const override {
Block *parent = nextIf->getBlock();
if (nextIf == &parent->front())
return failure();
auto prevIf = dyn_cast<IfOp>(nextIf->getPrevNode());
if (!prevIf)
return failure();
if (nextIf.condition() != prevIf.condition())
return failure();
// Don't permit merging if a result of the first if is used
// within the second.
if (llvm::any_of(prevIf->getUsers(),
[&](Operation *user) { return nextIf->isAncestor(user); }))
return failure();
SmallVector<Type> mergedTypes(prevIf.getResultTypes());
llvm::append_range(mergedTypes, nextIf.getResultTypes());
IfOp combinedIf = rewriter.create<IfOp>(
nextIf.getLoc(), mergedTypes, nextIf.condition(), /*hasElse=*/false);
rewriter.eraseBlock(&combinedIf.thenRegion().back());
YieldOp thenYield = prevIf.thenYield();
YieldOp thenYield2 = nextIf.thenYield();
combinedIf.thenRegion().getBlocks().splice(
combinedIf.thenRegion().getBlocks().begin(),
prevIf.thenRegion().getBlocks());
rewriter.mergeBlocks(nextIf.thenBlock(), combinedIf.thenBlock());
rewriter.setInsertionPointToEnd(combinedIf.thenBlock());
SmallVector<Value> mergedYields(thenYield.getOperands());
llvm::append_range(mergedYields, thenYield2.getOperands());
rewriter.create<YieldOp>(thenYield2.getLoc(), mergedYields);
rewriter.eraseOp(thenYield);
rewriter.eraseOp(thenYield2);
combinedIf.elseRegion().getBlocks().splice(
combinedIf.elseRegion().getBlocks().begin(),
prevIf.elseRegion().getBlocks());
if (!nextIf.elseRegion().empty()) {
if (combinedIf.elseRegion().empty()) {
combinedIf.elseRegion().getBlocks().splice(
combinedIf.elseRegion().getBlocks().begin(),
nextIf.elseRegion().getBlocks());
} else {
YieldOp elseYield = combinedIf.elseYield();
YieldOp elseYield2 = nextIf.elseYield();
rewriter.mergeBlocks(nextIf.elseBlock(), combinedIf.elseBlock());
rewriter.setInsertionPointToEnd(combinedIf.elseBlock());
SmallVector<Value> mergedElseYields(elseYield.getOperands());
llvm::append_range(mergedElseYields, elseYield2.getOperands());
rewriter.create<YieldOp>(elseYield2.getLoc(), mergedElseYields);
rewriter.eraseOp(elseYield);
rewriter.eraseOp(elseYield2);
}
}
SmallVector<Value> prevValues;
SmallVector<Value> nextValues;
for (auto pair : llvm::enumerate(combinedIf.getResults())) {
if (pair.index() < prevIf.getNumResults())
prevValues.push_back(pair.value());
else
nextValues.push_back(pair.value());
}
rewriter.replaceOp(prevIf, prevValues);
rewriter.replaceOp(nextIf, nextValues);
return success();
}
};
/// Pattern to remove an empty else branch.
struct RemoveEmptyElseBranch : public OpRewritePattern<IfOp> {
using OpRewritePattern<IfOp>::OpRewritePattern;
LogicalResult matchAndRewrite(IfOp ifOp,
PatternRewriter &rewriter) const override {
// Cannot remove else region when there are operation results.
if (ifOp.getNumResults())
return failure();
Block *elseBlock = ifOp.elseBlock();
if (!elseBlock || !llvm::hasSingleElement(*elseBlock))
return failure();
auto newIfOp = rewriter.cloneWithoutRegions(ifOp);
rewriter.inlineRegionBefore(ifOp.thenRegion(), newIfOp.thenRegion(),
newIfOp.thenRegion().begin());
rewriter.eraseOp(ifOp);
return success();
}
};
} // namespace
void IfOp::getCanonicalizationPatterns(RewritePatternSet &results,
MLIRContext *context) {
results
.add<RemoveUnusedResults, RemoveStaticCondition, ConvertTrivialIfToSelect,
ConditionPropagation, ReplaceIfYieldWithConditionOrValue, CombineIfs,
RemoveEmptyElseBranch>(context);
}
Block *IfOp::thenBlock() { return &thenRegion().back(); }
YieldOp IfOp::thenYield() { return cast<YieldOp>(&thenBlock()->back()); }
Block *IfOp::elseBlock() {
Region &r = elseRegion();
if (r.empty())
return nullptr;
return &r.back();
}
YieldOp IfOp::elseYield() { return cast<YieldOp>(&elseBlock()->back()); }
//===----------------------------------------------------------------------===//
// ParallelOp
//===----------------------------------------------------------------------===//
void ParallelOp::build(
OpBuilder &builder, OperationState &result, ValueRange lowerBounds,
ValueRange upperBounds, ValueRange steps, ValueRange initVals,
function_ref<void(OpBuilder &, Location, ValueRange, ValueRange)>
bodyBuilderFn) {
result.addOperands(lowerBounds);
result.addOperands(upperBounds);
result.addOperands(steps);
result.addOperands(initVals);
result.addAttribute(
ParallelOp::getOperandSegmentSizeAttr(),
builder.getI32VectorAttr({static_cast<int32_t>(lowerBounds.size()),
static_cast<int32_t>(upperBounds.size()),
static_cast<int32_t>(steps.size()),
static_cast<int32_t>(initVals.size())}));
result.addTypes(initVals.getTypes());
OpBuilder::InsertionGuard guard(builder);
unsigned numIVs = steps.size();
SmallVector<Type, 8> argTypes(numIVs, builder.getIndexType());
Region *bodyRegion = result.addRegion();
Block *bodyBlock = builder.createBlock(bodyRegion, {}, argTypes);
if (bodyBuilderFn) {
builder.setInsertionPointToStart(bodyBlock);
bodyBuilderFn(builder, result.location,
bodyBlock->getArguments().take_front(numIVs),
bodyBlock->getArguments().drop_front(numIVs));
}
ParallelOp::ensureTerminator(*bodyRegion, builder, result.location);
}
void ParallelOp::build(
OpBuilder &builder, OperationState &result, ValueRange lowerBounds,
ValueRange upperBounds, ValueRange steps,
function_ref<void(OpBuilder &, Location, ValueRange)> bodyBuilderFn) {
// Only pass a non-null wrapper if bodyBuilderFn is non-null itself. Make sure
// we don't capture a reference to a temporary by constructing the lambda at
// function level.
auto wrappedBuilderFn = [&bodyBuilderFn](OpBuilder &nestedBuilder,
Location nestedLoc, ValueRange ivs,
ValueRange) {
bodyBuilderFn(nestedBuilder, nestedLoc, ivs);
};
function_ref<void(OpBuilder &, Location, ValueRange, ValueRange)> wrapper;
if (bodyBuilderFn)
wrapper = wrappedBuilderFn;
build(builder, result, lowerBounds, upperBounds, steps, ValueRange(),
wrapper);
}
static LogicalResult verify(ParallelOp op) {
// Check that there is at least one value in lowerBound, upperBound and step.
// It is sufficient to test only step, because it is ensured already that the
// number of elements in lowerBound, upperBound and step are the same.
Operation::operand_range stepValues = op.step();
if (stepValues.empty())
return op.emitOpError(
"needs at least one tuple element for lowerBound, upperBound and step");
// Check whether all constant step values are positive.
for (Value stepValue : stepValues)
if (auto cst = stepValue.getDefiningOp<ConstantIndexOp>())
if (cst.getValue() <= 0)
return op.emitOpError("constant step operand must be positive");
// Check that the body defines the same number of block arguments as the
// number of tuple elements in step.
Block *body = op.getBody();
if (body->getNumArguments() != stepValues.size())
return op.emitOpError()
<< "expects the same number of induction variables: "
<< body->getNumArguments()
<< " as bound and step values: " << stepValues.size();
for (auto arg : body->getArguments())
if (!arg.getType().isIndex())
return op.emitOpError(
"expects arguments for the induction variable to be of index type");
// Check that the yield has no results
Operation *yield = body->getTerminator();
if (yield->getNumOperands() != 0)
return yield->emitOpError() << "not allowed to have operands inside '"
<< ParallelOp::getOperationName() << "'";
// Check that the number of results is the same as the number of ReduceOps.
SmallVector<ReduceOp, 4> reductions(body->getOps<ReduceOp>());
auto resultsSize = op.results().size();
auto reductionsSize = reductions.size();
auto initValsSize = op.initVals().size();
if (resultsSize != reductionsSize)
return op.emitOpError()
<< "expects number of results: " << resultsSize
<< " to be the same as number of reductions: " << reductionsSize;
if (resultsSize != initValsSize)
return op.emitOpError()
<< "expects number of results: " << resultsSize
<< " to be the same as number of initial values: " << initValsSize;
// Check that the types of the results and reductions are the same.
for (auto resultAndReduce : llvm::zip(op.results(), reductions)) {
auto resultType = std::get<0>(resultAndReduce).getType();
auto reduceOp = std::get<1>(resultAndReduce);
auto reduceType = reduceOp.operand().getType();
if (resultType != reduceType)
return reduceOp.emitOpError()
<< "expects type of reduce: " << reduceType
<< " to be the same as result type: " << resultType;
}
return success();
}
static ParseResult parseParallelOp(OpAsmParser &parser,
OperationState &result) {
auto &builder = parser.getBuilder();
// Parse an opening `(` followed by induction variables followed by `)`
SmallVector<OpAsmParser::OperandType, 4> ivs;
if (parser.parseRegionArgumentList(ivs, /*requiredOperandCount=*/-1,
OpAsmParser::Delimiter::Paren))
return failure();
// Parse loop bounds.
SmallVector<OpAsmParser::OperandType, 4> lower;
if (parser.parseEqual() ||
parser.parseOperandList(lower, ivs.size(),
OpAsmParser::Delimiter::Paren) ||
parser.resolveOperands(lower, builder.getIndexType(), result.operands))
return failure();
SmallVector<OpAsmParser::OperandType, 4> upper;
if (parser.parseKeyword("to") ||
parser.parseOperandList(upper, ivs.size(),
OpAsmParser::Delimiter::Paren) ||
parser.resolveOperands(upper, builder.getIndexType(), result.operands))
return failure();
// Parse step values.
SmallVector<OpAsmParser::OperandType, 4> steps;
if (parser.parseKeyword("step") ||
parser.parseOperandList(steps, ivs.size(),
OpAsmParser::Delimiter::Paren) ||
parser.resolveOperands(steps, builder.getIndexType(), result.operands))
return failure();
// Parse init values.
SmallVector<OpAsmParser::OperandType, 4> initVals;
if (succeeded(parser.parseOptionalKeyword("init"))) {
if (parser.parseOperandList(initVals, /*requiredOperandCount=*/-1,
OpAsmParser::Delimiter::Paren))
return failure();
}
// Parse optional results in case there is a reduce.
if (parser.parseOptionalArrowTypeList(result.types))
return failure();
// Now parse the body.
Region *body = result.addRegion();
SmallVector<Type, 4> types(ivs.size(), builder.getIndexType());
if (parser.parseRegion(*body, ivs, types))
return failure();
// Set `operand_segment_sizes` attribute.
result.addAttribute(
ParallelOp::getOperandSegmentSizeAttr(),
builder.getI32VectorAttr({static_cast<int32_t>(lower.size()),
static_cast<int32_t>(upper.size()),
static_cast<int32_t>(steps.size()),
static_cast<int32_t>(initVals.size())}));
// Parse attributes.
if (parser.parseOptionalAttrDict(result.attributes))
return failure();
if (!initVals.empty())
parser.resolveOperands(initVals, result.types, parser.getNameLoc(),
result.operands);
// Add a terminator if none was parsed.
ForOp::ensureTerminator(*body, builder, result.location);
return success();
}
static void print(OpAsmPrinter &p, ParallelOp op) {
p << op.getOperationName() << " (" << op.getBody()->getArguments() << ") = ("
<< op.lowerBound() << ") to (" << op.upperBound() << ") step (" << op.step()
<< ")";
if (!op.initVals().empty())
p << " init (" << op.initVals() << ")";
p.printOptionalArrowTypeList(op.getResultTypes());
p.printRegion(op.region(), /*printEntryBlockArgs=*/false);
p.printOptionalAttrDict(
op->getAttrs(), /*elidedAttrs=*/ParallelOp::getOperandSegmentSizeAttr());
}
Region &ParallelOp::getLoopBody() { return region(); }
bool ParallelOp::isDefinedOutsideOfLoop(Value value) {
return !region().isAncestor(value.getParentRegion());
}
LogicalResult ParallelOp::moveOutOfLoop(ArrayRef<Operation *> ops) {
for (auto *op : ops)
op->moveBefore(*this);
return success();
}
ParallelOp mlir::scf::getParallelForInductionVarOwner(Value val) {
auto ivArg = val.dyn_cast<BlockArgument>();
if (!ivArg)
return ParallelOp();
assert(ivArg.getOwner() && "unlinked block argument");
auto *containingOp = ivArg.getOwner()->getParentOp();
return dyn_cast<ParallelOp>(containingOp);
}
namespace {
// Collapse loop dimensions that perform a single iteration.
struct CollapseSingleIterationLoops : public OpRewritePattern<ParallelOp> {
using OpRewritePattern<ParallelOp>::OpRewritePattern;
LogicalResult matchAndRewrite(ParallelOp op,
PatternRewriter &rewriter) const override {
BlockAndValueMapping mapping;
// Compute new loop bounds that omit all single-iteration loop dimensions.
SmallVector<Value, 2> newLowerBounds;
SmallVector<Value, 2> newUpperBounds;
SmallVector<Value, 2> newSteps;
newLowerBounds.reserve(op.lowerBound().size());
newUpperBounds.reserve(op.upperBound().size());
newSteps.reserve(op.step().size());
for (auto dim : llvm::zip(op.lowerBound(), op.upperBound(), op.step(),
op.getInductionVars())) {
Value lowerBound, upperBound, step, iv;
std::tie(lowerBound, upperBound, step, iv) = dim;
// Collect the statically known loop bounds.
auto lowerBoundConstant =
dyn_cast_or_null<ConstantIndexOp>(lowerBound.getDefiningOp());
auto upperBoundConstant =
dyn_cast_or_null<ConstantIndexOp>(upperBound.getDefiningOp());
auto stepConstant =
dyn_cast_or_null<ConstantIndexOp>(step.getDefiningOp());
// Replace the loop induction variable by the lower bound if the loop
// performs a single iteration. Otherwise, copy the loop bounds.
if (lowerBoundConstant && upperBoundConstant && stepConstant &&
(upperBoundConstant.getValue() - lowerBoundConstant.getValue()) > 0 &&
(upperBoundConstant.getValue() - lowerBoundConstant.getValue()) <=
stepConstant.getValue()) {
mapping.map(iv, lowerBound);
} else {
newLowerBounds.push_back(lowerBound);
newUpperBounds.push_back(upperBound);
newSteps.push_back(step);
}
}
// Exit if none of the loop dimensions perform a single iteration.
if (newLowerBounds.size() == op.lowerBound().size())
return failure();
if (newLowerBounds.empty()) {
// All of the loop dimensions perform a single iteration. Inline
// loop body and nested ReduceOp's
SmallVector<Value> results;
results.reserve(op.initVals().size());
for (auto &bodyOp : op.getLoopBody().front().without_terminator()) {
auto reduce = dyn_cast<ReduceOp>(bodyOp);
if (!reduce) {
rewriter.clone(bodyOp, mapping);
continue;
}
Block &reduceBlock = reduce.reductionOperator().front();
auto initValIndex = results.size();
mapping.map(reduceBlock.getArgument(0), op.initVals()[initValIndex]);
mapping.map(reduceBlock.getArgument(1),
mapping.lookupOrDefault(reduce.operand()));
for (auto &reduceBodyOp : reduceBlock.without_terminator())
rewriter.clone(reduceBodyOp, mapping);
auto result = mapping.lookupOrDefault(
cast<ReduceReturnOp>(reduceBlock.getTerminator()).result());
results.push_back(result);
}
rewriter.replaceOp(op, results);
return success();
}
// Replace the parallel loop by lower-dimensional parallel loop.
auto newOp =
rewriter.create<ParallelOp>(op.getLoc(), newLowerBounds, newUpperBounds,
newSteps, op.initVals(), nullptr);
// Clone the loop body and remap the block arguments of the collapsed loops
// (inlining does not support a cancellable block argument mapping).
rewriter.cloneRegionBefore(op.region(), newOp.region(),
newOp.region().begin(), mapping);
rewriter.replaceOp(op, newOp.getResults());
return success();
}
};
/// Removes parallel loops in which at least one lower/upper bound pair consists
/// of the same values - such loops have an empty iteration domain.
struct RemoveEmptyParallelLoops : public OpRewritePattern<ParallelOp> {
using OpRewritePattern<ParallelOp>::OpRewritePattern;
LogicalResult matchAndRewrite(ParallelOp op,
PatternRewriter &rewriter) const override {
for (auto dim : llvm::zip(op.lowerBound(), op.upperBound())) {
if (std::get<0>(dim) == std::get<1>(dim)) {
rewriter.replaceOp(op, op.initVals());
return success();
}
}
return failure();
}
};
struct MergeNestedParallelLoops : public OpRewritePattern<ParallelOp> {
using OpRewritePattern<ParallelOp>::OpRewritePattern;
LogicalResult matchAndRewrite(ParallelOp op,
PatternRewriter &rewriter) const override {
Block &outerBody = op.getLoopBody().front();
if (!llvm::hasSingleElement(outerBody.without_terminator()))
return failure();
auto innerOp = dyn_cast<ParallelOp>(outerBody.front());
if (!innerOp)
return failure();
auto hasVal = [](const auto &range, Value val) {
return llvm::find(range, val) != range.end();
};
for (auto val : outerBody.getArguments())
if (hasVal(innerOp.lowerBound(), val) ||
hasVal(innerOp.upperBound(), val) || hasVal(innerOp.step(), val))
return failure();
// Reductions are not supported yet.
if (!op.initVals().empty() || !innerOp.initVals().empty())
return failure();
auto bodyBuilder = [&](OpBuilder &builder, Location /*loc*/,
ValueRange iterVals, ValueRange) {
Block &innerBody = innerOp.getLoopBody().front();
assert(iterVals.size() ==
(outerBody.getNumArguments() + innerBody.getNumArguments()));
BlockAndValueMapping mapping;
mapping.map(outerBody.getArguments(),
iterVals.take_front(outerBody.getNumArguments()));
mapping.map(innerBody.getArguments(),
iterVals.take_back(innerBody.getNumArguments()));
for (Operation &op : innerBody.without_terminator())
builder.clone(op, mapping);
};
auto concatValues = [](const auto &first, const auto &second) {
SmallVector<Value> ret;
ret.reserve(first.size() + second.size());
ret.assign(first.begin(), first.end());
ret.append(second.begin(), second.end());
return ret;
};
auto newLowerBounds = concatValues(op.lowerBound(), innerOp.lowerBound());
auto newUpperBounds = concatValues(op.upperBound(), innerOp.upperBound());
auto newSteps = concatValues(op.step(), innerOp.step());
rewriter.replaceOpWithNewOp<ParallelOp>(op, newLowerBounds, newUpperBounds,
newSteps, llvm::None, bodyBuilder);
return success();
}
};
} // namespace
void ParallelOp::getCanonicalizationPatterns(RewritePatternSet &results,
MLIRContext *context) {
results.add<CollapseSingleIterationLoops, RemoveEmptyParallelLoops,
MergeNestedParallelLoops>(context);
}
//===----------------------------------------------------------------------===//
// ReduceOp
//===----------------------------------------------------------------------===//
void ReduceOp::build(
OpBuilder &builder, OperationState &result, Value operand,
function_ref<void(OpBuilder &, Location, Value, Value)> bodyBuilderFn) {
auto type = operand.getType();
result.addOperands(operand);
OpBuilder::InsertionGuard guard(builder);
Region *bodyRegion = result.addRegion();
Block *body = builder.createBlock(bodyRegion, {}, ArrayRef<Type>{type, type});
if (bodyBuilderFn)
bodyBuilderFn(builder, result.location, body->getArgument(0),
body->getArgument(1));
}
static LogicalResult verify(ReduceOp op) {
// The region of a ReduceOp has two arguments of the same type as its operand.
auto type = op.operand().getType();
Block &block = op.reductionOperator().front();
if (block.empty())
return op.emitOpError("the block inside reduce should not be empty");
if (block.getNumArguments() != 2 ||
llvm::any_of(block.getArguments(), [&](const BlockArgument &arg) {
return arg.getType() != type;
}))
return op.emitOpError()
<< "expects two arguments to reduce block of type " << type;
// Check that the block is terminated by a ReduceReturnOp.
if (!isa<ReduceReturnOp>(block.getTerminator()))
return op.emitOpError("the block inside reduce should be terminated with a "
"'scf.reduce.return' op");
return success();
}
static ParseResult parseReduceOp(OpAsmParser &parser, OperationState &result) {
// Parse an opening `(` followed by the reduced value followed by `)`
OpAsmParser::OperandType operand;
if (parser.parseLParen() || parser.parseOperand(operand) ||
parser.parseRParen())
return failure();
Type resultType;
// Parse the type of the operand (and also what reduce computes on).
if (parser.parseColonType(resultType) ||
parser.resolveOperand(operand, resultType, result.operands))
return failure();
// Now parse the body.
Region *body = result.addRegion();
if (parser.parseRegion(*body, /*arguments=*/{}, /*argTypes=*/{}))
return failure();
return success();
}
static void print(OpAsmPrinter &p, ReduceOp op) {
p << op.getOperationName() << "(" << op.operand() << ") ";
p << " : " << op.operand().getType();
p.printRegion(op.reductionOperator());
}
//===----------------------------------------------------------------------===//
// ReduceReturnOp
//===----------------------------------------------------------------------===//
static LogicalResult verify(ReduceReturnOp op) {
// The type of the return value should be the same type as the type of the
// operand of the enclosing ReduceOp.
auto reduceOp = cast<ReduceOp>(op->getParentOp());
Type reduceType = reduceOp.operand().getType();
if (reduceType != op.result().getType())
return op.emitOpError() << "needs to have type " << reduceType
<< " (the type of the enclosing ReduceOp)";
return success();
}
//===----------------------------------------------------------------------===//
// WhileOp
//===----------------------------------------------------------------------===//
OperandRange WhileOp::getSuccessorEntryOperands(unsigned index) {
assert(index == 0 &&
"WhileOp is expected to branch only to the first region");
return inits();
}
ConditionOp WhileOp::getConditionOp() {
return cast<ConditionOp>(before().front().getTerminator());
}
Block::BlockArgListType WhileOp::getAfterArguments() {
return after().front().getArguments();
}
void WhileOp::getSuccessorRegions(Optional<unsigned> index,
ArrayRef<Attribute> operands,
SmallVectorImpl<RegionSuccessor> &regions) {
(void)operands;
if (!index.hasValue()) {
regions.emplace_back(&before(), before().getArguments());
return;
}
assert(*index < 2 && "there are only two regions in a WhileOp");
if (*index == 0) {
regions.emplace_back(&after(), after().getArguments());
regions.emplace_back(getResults());
return;
}
regions.emplace_back(&before(), before().getArguments());
}
/// Parses a `while` op.
///
/// op ::= `scf.while` assignments `:` function-type region `do` region
/// `attributes` attribute-dict
/// initializer ::= /* empty */ | `(` assignment-list `)`
/// assignment-list ::= assignment | assignment `,` assignment-list
/// assignment ::= ssa-value `=` ssa-value
static ParseResult parseWhileOp(OpAsmParser &parser, OperationState &result) {
SmallVector<OpAsmParser::OperandType, 4> regionArgs, operands;
Region *before = result.addRegion();
Region *after = result.addRegion();
OptionalParseResult listResult =
parser.parseOptionalAssignmentList(regionArgs, operands);
if (listResult.hasValue() && failed(listResult.getValue()))
return failure();
FunctionType functionType;
llvm::SMLoc typeLoc = parser.getCurrentLocation();
if (failed(parser.parseColonType(functionType)))
return failure();
result.addTypes(functionType.getResults());
if (functionType.getNumInputs() != operands.size()) {
return parser.emitError(typeLoc)
<< "expected as many input types as operands "
<< "(expected " << operands.size() << " got "
<< functionType.getNumInputs() << ")";
}
// Resolve input operands.
if (failed(parser.resolveOperands(operands, functionType.getInputs(),
parser.getCurrentLocation(),
result.operands)))
return failure();
return failure(
parser.parseRegion(*before, regionArgs, functionType.getInputs()) ||
parser.parseKeyword("do") || parser.parseRegion(*after) ||
parser.parseOptionalAttrDictWithKeyword(result.attributes));
}
/// Prints a `while` op.
static void print(OpAsmPrinter &p, scf::WhileOp op) {
p << op.getOperationName();
printInitializationList(p, op.before().front().getArguments(), op.inits(),
" ");
p << " : ";
p.printFunctionalType(op.inits().getTypes(), op.results().getTypes());
p.printRegion(op.before(), /*printEntryBlockArgs=*/false);
p << " do";
p.printRegion(op.after());
p.printOptionalAttrDictWithKeyword(op->getAttrs());
}
/// Verifies that two ranges of types match, i.e. have the same number of
/// entries and that types are pairwise equals. Reports errors on the given
/// operation in case of mismatch.
template <typename OpTy>
static LogicalResult verifyTypeRangesMatch(OpTy op, TypeRange left,
TypeRange right, StringRef message) {
if (left.size() != right.size())
return op.emitOpError("expects the same number of ") << message;
for (unsigned i = 0, e = left.size(); i < e; ++i) {
if (left[i] != right[i]) {
InFlightDiagnostic diag = op.emitOpError("expects the same types for ")
<< message;
diag.attachNote() << "for argument " << i << ", found " << left[i]
<< " and " << right[i];
return diag;
}
}
return success();
}
/// Verifies that the first block of the given `region` is terminated by a
/// YieldOp. Reports errors on the given operation if it is not the case.
template <typename TerminatorTy>
static TerminatorTy verifyAndGetTerminator(scf::WhileOp op, Region &region,
StringRef errorMessage) {
Operation *terminatorOperation = region.front().getTerminator();
if (auto yield = dyn_cast_or_null<TerminatorTy>(terminatorOperation))
return yield;
auto diag = op.emitOpError(errorMessage);
if (terminatorOperation)
diag.attachNote(terminatorOperation->getLoc()) << "terminator here";
return nullptr;
}
static LogicalResult verify(scf::WhileOp op) {
if (failed(RegionBranchOpInterface::verifyTypes(op)))
return failure();
auto beforeTerminator = verifyAndGetTerminator<scf::ConditionOp>(
op, op.before(),
"expects the 'before' region to terminate with 'scf.condition'");
if (!beforeTerminator)
return failure();
TypeRange trailingTerminatorOperands = beforeTerminator.args().getTypes();
if (failed(verifyTypeRangesMatch(op, trailingTerminatorOperands,
op.after().getArgumentTypes(),
"trailing operands of the 'before' block "
"terminator and 'after' region arguments")))
return failure();
if (failed(verifyTypeRangesMatch(
op, trailingTerminatorOperands, op.getResultTypes(),
"trailing operands of the 'before' block terminator and op results")))
return failure();
auto afterTerminator = verifyAndGetTerminator<scf::YieldOp>(
op, op.after(),
"expects the 'after' region to terminate with 'scf.yield'");
return success(afterTerminator != nullptr);
}
namespace {
/// Replace uses of the condition within the do block with true, since otherwise
/// the block would not be evaluated.
///
/// scf.while (..) : (i1, ...) -> ... {
/// %condition = call @evaluate_condition() : () -> i1
/// scf.condition(%condition) %condition : i1, ...
/// } do {
/// ^bb0(%arg0: i1, ...):
/// use(%arg0)
/// ...
///
/// becomes
/// scf.while (..) : (i1, ...) -> ... {
/// %condition = call @evaluate_condition() : () -> i1
/// scf.condition(%condition) %condition : i1, ...
/// } do {
/// ^bb0(%arg0: i1, ...):
/// use(%true)
/// ...
struct WhileConditionTruth : public OpRewritePattern<WhileOp> {
using OpRewritePattern<WhileOp>::OpRewritePattern;
LogicalResult matchAndRewrite(WhileOp op,
PatternRewriter &rewriter) const override {
auto term = op.getConditionOp();
// These variables serve to prevent creating duplicate constants
// and hold constant true or false values.
Value constantTrue = nullptr;
bool replaced = false;
for (auto yieldedAndBlockArgs :
llvm::zip(term.args(), op.getAfterArguments())) {
if (std::get<0>(yieldedAndBlockArgs) == term.condition()) {
if (!std::get<1>(yieldedAndBlockArgs).use_empty()) {
if (!constantTrue)
constantTrue = rewriter.create<mlir::ConstantOp>(
op.getLoc(), term.condition().getType(),
rewriter.getBoolAttr(true));
std::get<1>(yieldedAndBlockArgs).replaceAllUsesWith(constantTrue);
replaced = true;
}
}
}
return success(replaced);
}
};
} // namespace
void WhileOp::getCanonicalizationPatterns(OwningRewritePatternList &results,
MLIRContext *context) {
results.insert<WhileConditionTruth>(context);
}
//===----------------------------------------------------------------------===//
// TableGen'd op method definitions
//===----------------------------------------------------------------------===//
#define GET_OP_CLASSES
#include "mlir/Dialect/SCF/SCFOps.cpp.inc"
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