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[mlir][AffineOps] Adds affine loop fusion transformation function to LoopFusionUtils. 

Summary:
Adds affine loop fusion transformation function to LoopFusionUtils.
Updates TestLoopFusion utility to run loop fusion transformation until a fixed point is reached.
Adds unit tests to test the transformation.
Includes ASAN bug fix for D73190.

Reviewers: bondhugula, dcaballe

Reviewed By: bondhugula, dcaballe

Subscribers: mehdi_amini, rriddle, jpienaar, burmako, shauheen, antiagainst, nicolasvasilache, arpith-jacob, mgester, lucyrfox, aartbik, liufengdb, Joonsoo, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74330
This commit is contained in:
Andy Davis 2020-02-11 13:30:49 -08:00
parent 20a604d3f5
commit 40b2eb3530
4 changed files with 215 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
mlir/include/mlir/Transforms/LoopFusionUtils.h
View File

@ -51,6 +51,11 @@ FusionResult canFuseLoops(AffineForOp srcForOp, AffineForOp dstForOp,
unsigned dstLoopDepth,
ComputationSliceState *srcSlice);
/// Fuses 'srcForOp' into 'dstForOp' with destination loop block insertion point
/// and source slice loop bounds specified in 'srcSlice'.
void fuseLoops(AffineForOp srcForOp, AffineForOp dstForOp,
ComputationSliceState *srcSlice);
/// LoopNestStats aggregates various per-loop statistics (eg. loop trip count
/// and operation count) for a loop nest up until (and including) the innermost
/// loop body.

29
mlir/lib/Transforms/Utils/LoopFusionUtils.cpp
View File

@ -24,6 +24,7 @@
#include "mlir/IR/Builders.h"
#include "mlir/IR/Function.h"
#include "mlir/IR/Operation.h"
#include "mlir/Transforms/LoopUtils.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/Debug.h"
@ -246,6 +247,34 @@ FusionResult mlir::canFuseLoops(AffineForOp srcForOp, AffineForOp dstForOp,
return FusionResult::Success;
}
/// Fuses 'srcForOp' into 'dstForOp' with destination loop block insertion point
/// and source slice loop bounds specified in 'srcSlice'.
void mlir::fuseLoops(AffineForOp srcForOp, AffineForOp dstForOp,
ComputationSliceState *srcSlice) {
// Clone 'srcForOp' into 'dstForOp' at 'srcSlice->insertPoint'.
OpBuilder b(srcSlice->insertPoint->getBlock(), srcSlice->insertPoint);
BlockAndValueMapping mapper;
b.clone(*srcForOp, mapper);
// Update 'sliceLoopNest' upper and lower bounds from computed 'srcSlice'.
SmallVector<AffineForOp, 4> sliceLoops;
for (unsigned i = 0, e = srcSlice->ivs.size(); i < e; ++i) {
auto loopIV = mapper.lookupOrNull(srcSlice->ivs[i]);
if (!loopIV)
continue;
auto forOp = getForInductionVarOwner(loopIV);
sliceLoops.push_back(forOp);
if (AffineMap lbMap = srcSlice->lbs[i])
forOp.setLowerBound(srcSlice->lbOperands[i], lbMap);
if (AffineMap ubMap = srcSlice->ubs[i])
forOp.setUpperBound(srcSlice->ubOperands[i], ubMap);
}
// Promote any single iteration slice loops.
for (AffineForOp forOp : sliceLoops)
promoteIfSingleIteration(forOp);
}
/// Collect loop nest statistics (eg. loop trip count and operation count)
/// in 'stats' for loop nest rooted at 'forOp'. Returns true on success,
/// returns false otherwise.

105
mlir/test/Transforms/loop-fusion-transformation.mlir Normal file
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@ -0,0 +1,105 @@
// RUN: mlir-opt %s -test-loop-fusion -test-loop-fusion-transformation -split-input-file -canonicalize | FileCheck %s
// CHECK-LABEL: func @slice_depth1_loop_nest() {
func @slice_depth1_loop_nest() {
%0 = alloc() : memref<100xf32>
%cst = constant 7.000000e+00 : f32
affine.for %i0 = 0 to 16 {
affine.store %cst, %0[%i0] : memref<100xf32>
}
affine.for %i1 = 0 to 5 {
%1 = affine.load %0[%i1] : memref<100xf32>
}
// CHECK: affine.for %[[IV0:.*]] = 0 to 5 {
// CHECK-NEXT: affine.store %{{.*}}, %{{.*}}[%[[IV0]]] : memref<100xf32>
// CHECK-NEXT: affine.load %{{.*}}[%[[IV0]]] : memref<100xf32>
// CHECK-NEXT: }
// CHECK-NEXT: return
return
}
// -----
// CHECK-LABEL: func @should_fuse_reduction_to_pointwise() {
func @should_fuse_reduction_to_pointwise() {
%a = alloc() : memref<10x10xf32>
%b = alloc() : memref<10xf32>
%c = alloc() : memref<10xf32>
%cf7 = constant 7.0 : f32
affine.for %i0 = 0 to 10 {
affine.for %i1 = 0 to 10 {
%v0 = affine.load %b[%i0] : memref<10xf32>
%v1 = affine.load %a[%i0, %i1] : memref<10x10xf32>
%v3 = addf %v0, %v1 : f32
affine.store %v3, %b[%i0] : memref<10xf32>
}
}
affine.for %i2 = 0 to 10 {
%v4 = affine.load %b[%i2] : memref<10xf32>
affine.store %v4, %c[%i2] : memref<10xf32>
}
// Match on the fused loop nest.
// Should fuse in entire inner loop on %i1 from source loop nest, as %i1
// is not used in the access function of the store/load on %b.
// CHECK: affine.for %{{.*}} = 0 to 10 {
// CHECK-NEXT: affine.for %{{.*}} = 0 to 10 {
// CHECK-NEXT: affine.load %{{.*}}[%{{.*}}] : memref<10xf32>
// CHECK-NEXT: affine.load %{{.*}}[%{{.*}}, %{{.*}}] : memref<10x10xf32>
// CHECK-NEXT: addf %{{.*}}, %{{.*}} : f32
// CHECK-NEXT: affine.store %{{.*}}, %{{.*}}[%{{.*}}] : memref<10xf32>
// CHECK-NEXT: }
// CHECK-NEXT: affine.load %{{.*}}[%{{.*}}] : memref<10xf32>
// CHECK-NEXT: affine.store %{{.*}}, %{{.*}}[%{{.*}}] : memref<10xf32>
// CHECK-NEXT: }
// CHECK-NEXT: return
return
}
// -----
// CHECK-LABEL: func @should_fuse_avoiding_dependence_cycle() {
func @should_fuse_avoiding_dependence_cycle() {
%a = alloc() : memref<10xf32>
%b = alloc() : memref<10xf32>
%c = alloc() : memref<10xf32>
%cf7 = constant 7.0 : f32
// Set up the following dependences:
// 1) loop0 -> loop1 on memref '%{{.*}}'
// 2) loop0 -> loop2 on memref '%{{.*}}'
// 3) loop1 -> loop2 on memref '%{{.*}}'
affine.for %i0 = 0 to 10 {
%v0 = affine.load %a[%i0] : memref<10xf32>
affine.store %cf7, %b[%i0] : memref<10xf32>
}
affine.for %i1 = 0 to 10 {
affine.store %cf7, %a[%i1] : memref<10xf32>
%v1 = affine.load %c[%i1] : memref<10xf32>
}
affine.for %i2 = 0 to 10 {
%v2 = affine.load %b[%i2] : memref<10xf32>
affine.store %cf7, %c[%i2] : memref<10xf32>
}
// Fusing loop first loop into last would create a cycle:
// {1} <--> {0, 2}
// However, we can avoid the dependence cycle if we first fuse loop0 into
// loop1:
// {0, 1) --> {2}
// Then fuse this loop nest with loop2:
// {0, 1, 2}
//
// CHECK: affine.for %{{.*}} = 0 to 10 {
// CHECK-NEXT: affine.load %{{.*}}[%{{.*}}] : memref<10xf32>
// CHECK-NEXT: affine.store %{{.*}}, %{{.*}}[%{{.*}}] : memref<10xf32>
// CHECK-NEXT: affine.store %{{.*}}, %{{.*}}[%{{.*}}] : memref<10xf32>
// CHECK-NEXT: affine.load %{{.*}}[%{{.*}}] : memref<10xf32>
// CHECK-NEXT: affine.load %{{.*}}[%{{.*}}] : memref<10xf32>
// CHECK-NEXT: affine.store %{{.*}}, %{{.*}}[%{{.*}}] : memref<10xf32>
// CHECK-NEXT: }
// CHECK-NEXT: return
return
}

96
mlir/test/lib/Transforms/TestLoopFusion.cpp
View File

@ -41,6 +41,11 @@ static llvm::cl::opt<bool> clTestSliceComputation(
llvm::cl::desc("Enable testing of loop fusion slice computation"),
llvm::cl::cat(clOptionsCategory));
static llvm::cl::opt<bool> clTestLoopFusionTransformation(
"test-loop-fusion-transformation",
llvm::cl::desc("Enable testing of loop fusion transformation"),
llvm::cl::cat(clOptionsCategory));
namespace {
struct TestLoopFusion : public FunctionPass<TestLoopFusion> {
@ -69,11 +74,10 @@ gatherLoops(Block *block, unsigned currLoopDepth,
// Run fusion dependence check on 'loops[i]' and 'loops[j]' at loop depths
// in range ['loopDepth' + 1, 'maxLoopDepth'].
// Emits a remark on 'loops[i]' if a fusion-preventing dependence exists.
static void testDependenceCheck(SmallVector<AffineForOp, 2> &loops, unsigned i,
unsigned j, unsigned loopDepth,
// Returns false as IR is not transformed.
static bool testDependenceCheck(AffineForOp srcForOp, AffineForOp dstForOp,
unsigned i, unsigned j, unsigned loopDepth,
unsigned maxLoopDepth) {
AffineForOp srcForOp = loops[i];
AffineForOp dstForOp = loops[j];
mlir::ComputationSliceState sliceUnion;
for (unsigned d = loopDepth + 1; d <= maxLoopDepth; ++d) {
FusionResult result =
@ -84,6 +88,7 @@ static void testDependenceCheck(SmallVector<AffineForOp, 2> &loops, unsigned i,
<< i << " into loop nest " << j << " at depth " << loopDepth;
}
}
return false;
}
// Returns the index of 'op' in its block.
@ -121,11 +126,10 @@ static std::string getSliceStr(const mlir::ComputationSliceState &sliceUnion) {
// Computes fusion slice union on 'loops[i]' and 'loops[j]' at loop depths
// in range ['loopDepth' + 1, 'maxLoopDepth'].
// Emits a string representation of the slice union as a remark on 'loops[j]'.
static void testSliceComputation(SmallVector<AffineForOp, 2> &loops, unsigned i,
unsigned j, unsigned loopDepth,
// Returns false as IR is not transformed.
static bool testSliceComputation(AffineForOp forOpA, AffineForOp forOpB,
unsigned i, unsigned j, unsigned loopDepth,
unsigned maxLoopDepth) {
AffineForOp forOpA = loops[i];
AffineForOp forOpB = loops[j];
for (unsigned d = loopDepth + 1; d <= maxLoopDepth; ++d) {
mlir::ComputationSliceState sliceUnion;
FusionResult result = mlir::canFuseLoops(forOpA, forOpB, d, &sliceUnion);
@ -135,31 +139,83 @@ static void testSliceComputation(SmallVector<AffineForOp, 2> &loops, unsigned i,
<< " : " << getSliceStr(sliceUnion) << ")";
}
}
return false;
}
void TestLoopFusion::runOnFunction() {
// Gather all AffineForOps by loop depth.
DenseMap<unsigned, SmallVector<AffineForOp, 2>> depthToLoops;
for (auto &block : getFunction()) {
gatherLoops(&block, /*currLoopDepth=*/0, depthToLoops);
// Attempts to fuse 'forOpA' into 'forOpB' at loop depths in range
// ['loopDepth' + 1, 'maxLoopDepth'].
// Returns true if loops were successfully fused, false otherwise.
static bool testLoopFusionTransformation(AffineForOp forOpA, AffineForOp forOpB,
unsigned i, unsigned j,
unsigned loopDepth,
unsigned maxLoopDepth) {
for (unsigned d = loopDepth + 1; d <= maxLoopDepth; ++d) {
mlir::ComputationSliceState sliceUnion;
FusionResult result = mlir::canFuseLoops(forOpA, forOpB, d, &sliceUnion);
if (result.value == FusionResult::Success) {
mlir::fuseLoops(forOpA, forOpB, &sliceUnion);
// Note: 'forOpA' is removed to simplify test output. A proper loop
// fusion pass should check the data dependence graph and run memref
// region analysis to ensure removing 'forOpA' is safe.
forOpA.erase();
return true;
}
}
return false;
}
// Run tests on all combinations of src/dst loop nests in 'depthToLoops'.
using LoopFunc = function_ref<bool(AffineForOp, AffineForOp, unsigned, unsigned,
unsigned, unsigned)>;
// Run tests on all combinations of src/dst loop nests in 'depthToLoops'.
// If 'return_on_change' is true, returns on first invocation of 'fn' which
// returns true.
static bool
iterateLoops(DenseMap<unsigned, SmallVector<AffineForOp, 2>> &depthToLoops,
LoopFunc fn, bool return_on_change = false) {
bool changed = false;
for (auto &depthAndLoops : depthToLoops) {
unsigned loopDepth = depthAndLoops.first;
auto &loops = depthAndLoops.second;
unsigned numLoops = loops.size();
for (unsigned j = 0; j < numLoops; ++j) {
for (unsigned k = 0; k < numLoops; ++k) {
if (j == k)
continue;
if (clTestDependenceCheck)
testDependenceCheck(loops, j, k, loopDepth, depthToLoops.size());
if (clTestSliceComputation)
testSliceComputation(loops, j, k, loopDepth, depthToLoops.size());
if (j != k)
changed |=
fn(loops[j], loops[k], j, k, loopDepth, depthToLoops.size());
if (changed && return_on_change)
return true;
}
}
}
return changed;
}
void TestLoopFusion::runOnFunction() {
DenseMap<unsigned, SmallVector<AffineForOp, 2>> depthToLoops;
if (clTestLoopFusionTransformation) {
// Run loop fusion until a fixed point is reached.
do {
depthToLoops.clear();
// Gather all AffineForOps by loop depth.
for (auto &block : getFunction())
gatherLoops(&block, /*currLoopDepth=*/0, depthToLoops);
// Try to fuse all combinations of src/dst loop nests in 'depthToLoops'.
} while (iterateLoops(depthToLoops, testLoopFusionTransformation,
/*return_on_change=*/true));
return;
}
// Gather all AffineForOps by loop depth.
for (Block &block : getFunction())
gatherLoops(&block, /*currLoopDepth=*/0, depthToLoops);
// Run tests on all combinations of src/dst loop nests in 'depthToLoops'.
if (clTestDependenceCheck)
iterateLoops(depthToLoops, testDependenceCheck);
if (clTestSliceComputation)
iterateLoops(depthToLoops, testSliceComputation);
}
static PassRegistration<TestLoopFusion>