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llvm-project/llvm/lib/Transforms/Utils/PredicateInfo.cpp

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//===-- PredicateInfo.cpp - PredicateInfo Builder--------------------===//
//
// 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
//
//===----------------------------------------------------------------===//
//
// This file implements the PredicateInfo class.
//
//===----------------------------------------------------------------===//
#include "llvm/Transforms/Utils/PredicateInfo.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/IR/AssemblyAnnotationWriter.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/DebugCounter.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Transforms/Utils.h"
#include <algorithm>
#define DEBUG_TYPE "predicateinfo"
using namespace llvm;
using namespace PatternMatch;
INITIALIZE_PASS_BEGIN(PredicateInfoPrinterLegacyPass, "print-predicateinfo",
"PredicateInfo Printer", false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_END(PredicateInfoPrinterLegacyPass, "print-predicateinfo",
"PredicateInfo Printer", false, false)
static cl::opt<bool> VerifyPredicateInfo(
"verify-predicateinfo", cl::init(false), cl::Hidden,
cl::desc("Verify PredicateInfo in legacy printer pass."));
DEBUG_COUNTER(RenameCounter, "predicateinfo-rename",
"Controls which variables are renamed with predicateinfo");
// Maximum number of conditions considered for renaming for each branch/assume.
// This limits renaming of deep and/or chains.
static const unsigned MaxCondsPerBranch = 8;
namespace {
// Given a predicate info that is a type of branching terminator, get the
// branching block.
const BasicBlock *getBranchBlock(const PredicateBase *PB) {
assert(isa<PredicateWithEdge>(PB) &&
"Only branches and switches should have PHIOnly defs that "
"require branch blocks.");
return cast<PredicateWithEdge>(PB)->From;
}
// Given a predicate info that is a type of branching terminator, get the
// branching terminator.
static Instruction *getBranchTerminator(const PredicateBase *PB) {
assert(isa<PredicateWithEdge>(PB) &&
"Not a predicate info type we know how to get a terminator from.");
return cast<PredicateWithEdge>(PB)->From->getTerminator();
}
// Given a predicate info that is a type of branching terminator, get the
// edge this predicate info represents
std::pair<BasicBlock *, BasicBlock *> getBlockEdge(const PredicateBase *PB) {
assert(isa<PredicateWithEdge>(PB) &&
"Not a predicate info type we know how to get an edge from.");
const auto *PEdge = cast<PredicateWithEdge>(PB);
return std::make_pair(PEdge->From, PEdge->To);
}
}
namespace llvm {
enum LocalNum {
// Operations that must appear first in the block.
LN_First,
// Operations that are somewhere in the middle of the block, and are sorted on
// demand.
LN_Middle,
// Operations that must appear last in a block, like successor phi node uses.
LN_Last
};
// Associate global and local DFS info with defs and uses, so we can sort them
// into a global domination ordering.
struct ValueDFS {
int DFSIn = 0;
int DFSOut = 0;
unsigned int LocalNum = LN_Middle;
// Only one of Def or Use will be set.
Value *Def = nullptr;
Use *U = nullptr;
// Neither PInfo nor EdgeOnly participate in the ordering
PredicateBase *PInfo = nullptr;
bool EdgeOnly = false;
};
// Perform a strict weak ordering on instructions and arguments.
static bool valueComesBefore(const Value *A, const Value *B) {
auto *ArgA = dyn_cast_or_null<Argument>(A);
auto *ArgB = dyn_cast_or_null<Argument>(B);
if (ArgA && !ArgB)
return true;
if (ArgB && !ArgA)
return false;
if (ArgA && ArgB)
return ArgA->getArgNo() < ArgB->getArgNo();
return cast<Instruction>(A)->comesBefore(cast<Instruction>(B));
}
// This compares ValueDFS structures. Doing so allows us to walk the minimum
// number of instructions necessary to compute our def/use ordering.
struct ValueDFS_Compare {
DominatorTree &DT;
ValueDFS_Compare(DominatorTree &DT) : DT(DT) {}
bool operator()(const ValueDFS &A, const ValueDFS &B) const {
if (&A == &B)
return false;
// The only case we can't directly compare them is when they in the same
// block, and both have localnum == middle. In that case, we have to use
// comesbefore to see what the real ordering is, because they are in the
// same basic block.
assert((A.DFSIn != B.DFSIn || A.DFSOut == B.DFSOut) &&
"Equal DFS-in numbers imply equal out numbers");
bool SameBlock = A.DFSIn == B.DFSIn;
// We want to put the def that will get used for a given set of phi uses,
// before those phi uses.
// So we sort by edge, then by def.
// Note that only phi nodes uses and defs can come last.
if (SameBlock && A.LocalNum == LN_Last && B.LocalNum == LN_Last)
return comparePHIRelated(A, B);
bool isADef = A.Def;
bool isBDef = B.Def;
if (!SameBlock || A.LocalNum != LN_Middle || B.LocalNum != LN_Middle)
return std::tie(A.DFSIn, A.LocalNum, isADef) <
std::tie(B.DFSIn, B.LocalNum, isBDef);
return localComesBefore(A, B);
}
// For a phi use, or a non-materialized def, return the edge it represents.
std::pair<BasicBlock *, BasicBlock *> getBlockEdge(const ValueDFS &VD) const {
if (!VD.Def && VD.U) {
auto *PHI = cast<PHINode>(VD.U->getUser());
return std::make_pair(PHI->getIncomingBlock(*VD.U), PHI->getParent());
}
// This is really a non-materialized def.
return ::getBlockEdge(VD.PInfo);
}
// For two phi related values, return the ordering.
bool comparePHIRelated(const ValueDFS &A, const ValueDFS &B) const {
BasicBlock *ASrc, *ADest, *BSrc, *BDest;
std::tie(ASrc, ADest) = getBlockEdge(A);
std::tie(BSrc, BDest) = getBlockEdge(B);
#ifndef NDEBUG
// This function should only be used for values in the same BB, check that.
DomTreeNode *DomASrc = DT.getNode(ASrc);
DomTreeNode *DomBSrc = DT.getNode(BSrc);
assert(DomASrc->getDFSNumIn() == (unsigned)A.DFSIn &&
"DFS numbers for A should match the ones of the source block");
assert(DomBSrc->getDFSNumIn() == (unsigned)B.DFSIn &&
"DFS numbers for B should match the ones of the source block");
assert(A.DFSIn == B.DFSIn && "Values must be in the same block");
#endif
(void)ASrc;
(void)BSrc;
// Use DFS numbers to compare destination blocks, to guarantee a
// deterministic order.
DomTreeNode *DomADest = DT.getNode(ADest);
DomTreeNode *DomBDest = DT.getNode(BDest);
unsigned AIn = DomADest->getDFSNumIn();
unsigned BIn = DomBDest->getDFSNumIn();
bool isADef = A.Def;
bool isBDef = B.Def;
assert((!A.Def || !A.U) && (!B.Def || !B.U) &&
"Def and U cannot be set at the same time");
// Now sort by edge destination and then defs before uses.
return std::tie(AIn, isADef) < std::tie(BIn, isBDef);
}
// Get the definition of an instruction that occurs in the middle of a block.
Value *getMiddleDef(const ValueDFS &VD) const {
if (VD.Def)
return VD.Def;
// It's possible for the defs and uses to be null. For branches, the local
// numbering will say the placed predicaeinfos should go first (IE
// LN_beginning), so we won't be in this function. For assumes, we will end
// up here, beause we need to order the def we will place relative to the
// assume. So for the purpose of ordering, we pretend the def is right
// after the assume, because that is where we will insert the info.
if (!VD.U) {
assert(VD.PInfo &&
"No def, no use, and no predicateinfo should not occur");
assert(isa<PredicateAssume>(VD.PInfo) &&
"Middle of block should only occur for assumes");
return cast<PredicateAssume>(VD.PInfo)->AssumeInst->getNextNode();
}
return nullptr;
}
// Return either the Def, if it's not null, or the user of the Use, if the def
// is null.
const Instruction *getDefOrUser(const Value *Def, const Use *U) const {
if (Def)
return cast<Instruction>(Def);
return cast<Instruction>(U->getUser());
}
// This performs the necessary local basic block ordering checks to tell
// whether A comes before B, where both are in the same basic block.
bool localComesBefore(const ValueDFS &A, const ValueDFS &B) const {
auto *ADef = getMiddleDef(A);
auto *BDef = getMiddleDef(B);
// See if we have real values or uses. If we have real values, we are
// guaranteed they are instructions or arguments. No matter what, we are
// guaranteed they are in the same block if they are instructions.
auto *ArgA = dyn_cast_or_null<Argument>(ADef);
auto *ArgB = dyn_cast_or_null<Argument>(BDef);
if (ArgA || ArgB)
return valueComesBefore(ArgA, ArgB);
auto *AInst = getDefOrUser(ADef, A.U);
auto *BInst = getDefOrUser(BDef, B.U);
return valueComesBefore(AInst, BInst);
}
};
class PredicateInfoBuilder {
// Used to store information about each value we might rename.
struct ValueInfo {
SmallVector<PredicateBase *, 4> Infos;
};
PredicateInfo &PI;
Function &F;
DominatorTree &DT;
AssumptionCache &AC;
// This stores info about each operand or comparison result we make copies
// of. The real ValueInfos start at index 1, index 0 is unused so that we
// can more easily detect invalid indexing.
SmallVector<ValueInfo, 32> ValueInfos;
// This gives the index into the ValueInfos array for a given Value. Because
// 0 is not a valid Value Info index, you can use DenseMap::lookup and tell
// whether it returned a valid result.
DenseMap<Value *, unsigned int> ValueInfoNums;
// The set of edges along which we can only handle phi uses, due to critical
// edges.
DenseSet<std::pair<BasicBlock *, BasicBlock *>> EdgeUsesOnly;
ValueInfo &getOrCreateValueInfo(Value *);
const ValueInfo &getValueInfo(Value *) const;
void processAssume(IntrinsicInst *, BasicBlock *,
SmallVectorImpl<Value *> &OpsToRename);
void processBranch(BranchInst *, BasicBlock *,
SmallVectorImpl<Value *> &OpsToRename);
void processSwitch(SwitchInst *, BasicBlock *,
SmallVectorImpl<Value *> &OpsToRename);
void renameUses(SmallVectorImpl<Value *> &OpsToRename);
void addInfoFor(SmallVectorImpl<Value *> &OpsToRename, Value *Op,
PredicateBase *PB);
typedef SmallVectorImpl<ValueDFS> ValueDFSStack;
void convertUsesToDFSOrdered(Value *, SmallVectorImpl<ValueDFS> &);
Value *materializeStack(unsigned int &, ValueDFSStack &, Value *);
bool stackIsInScope(const ValueDFSStack &, const ValueDFS &) const;
void popStackUntilDFSScope(ValueDFSStack &, const ValueDFS &);
public:
PredicateInfoBuilder(PredicateInfo &PI, Function &F, DominatorTree &DT,
AssumptionCache &AC)
: PI(PI), F(F), DT(DT), AC(AC) {
// Push an empty operand info so that we can detect 0 as not finding one
ValueInfos.resize(1);
}
void buildPredicateInfo();
};
bool PredicateInfoBuilder::stackIsInScope(const ValueDFSStack &Stack,
const ValueDFS &VDUse) const {
if (Stack.empty())
return false;
// If it's a phi only use, make sure it's for this phi node edge, and that the
// use is in a phi node. If it's anything else, and the top of the stack is
// EdgeOnly, we need to pop the stack. We deliberately sort phi uses next to
// the defs they must go with so that we can know it's time to pop the stack
// when we hit the end of the phi uses for a given def.
if (Stack.back().EdgeOnly) {
if (!VDUse.U)
return false;
auto *PHI = dyn_cast<PHINode>(VDUse.U->getUser());
if (!PHI)
return false;
// Check edge
BasicBlock *EdgePred = PHI->getIncomingBlock(*VDUse.U);
if (EdgePred != getBranchBlock(Stack.back().PInfo))
return false;
// Use dominates, which knows how to handle edge dominance.
return DT.dominates(getBlockEdge(Stack.back().PInfo), *VDUse.U);
}
return (VDUse.DFSIn >= Stack.back().DFSIn &&
VDUse.DFSOut <= Stack.back().DFSOut);
}
void PredicateInfoBuilder::popStackUntilDFSScope(ValueDFSStack &Stack,
const ValueDFS &VD) {
while (!Stack.empty() && !stackIsInScope(Stack, VD))
Stack.pop_back();
}
// Convert the uses of Op into a vector of uses, associating global and local
// DFS info with each one.
void PredicateInfoBuilder::convertUsesToDFSOrdered(
Value *Op, SmallVectorImpl<ValueDFS> &DFSOrderedSet) {
for (auto &U : Op->uses()) {
if (auto *I = dyn_cast<Instruction>(U.getUser())) {
ValueDFS VD;
// Put the phi node uses in the incoming block.
BasicBlock *IBlock;
if (auto *PN = dyn_cast<PHINode>(I)) {
IBlock = PN->getIncomingBlock(U);
// Make phi node users appear last in the incoming block
// they are from.
VD.LocalNum = LN_Last;
} else {
// If it's not a phi node use, it is somewhere in the middle of the
// block.
IBlock = I->getParent();
VD.LocalNum = LN_Middle;
}
DomTreeNode *DomNode = DT.getNode(IBlock);
// It's possible our use is in an unreachable block. Skip it if so.
if (!DomNode)
continue;
VD.DFSIn = DomNode->getDFSNumIn();
VD.DFSOut = DomNode->getDFSNumOut();
VD.U = &U;
DFSOrderedSet.push_back(VD);
}
}
}
bool shouldRename(Value *V) {
// Only want real values, not constants. Additionally, operands with one use
// are only being used in the comparison, which means they will not be useful
// for us to consider for predicateinfo.
return (isa<Instruction>(V) || isa<Argument>(V)) && !V->hasOneUse();
}
// Collect relevant operations from Comparison that we may want to insert copies
// for.
void collectCmpOps(CmpInst *Comparison, SmallVectorImpl<Value *> &CmpOperands) {
auto *Op0 = Comparison->getOperand(0);
auto *Op1 = Comparison->getOperand(1);
if (Op0 == Op1)
return;
CmpOperands.push_back(Op0);
CmpOperands.push_back(Op1);
}
// Add Op, PB to the list of value infos for Op, and mark Op to be renamed.
void PredicateInfoBuilder::addInfoFor(SmallVectorImpl<Value *> &OpsToRename,
Value *Op, PredicateBase *PB) {
auto &OperandInfo = getOrCreateValueInfo(Op);
if (OperandInfo.Infos.empty())
OpsToRename.push_back(Op);
PI.AllInfos.push_back(PB);
OperandInfo.Infos.push_back(PB);
}
// Process an assume instruction and place relevant operations we want to rename
// into OpsToRename.
void PredicateInfoBuilder::processAssume(
IntrinsicInst *II, BasicBlock *AssumeBB,
SmallVectorImpl<Value *> &OpsToRename) {
SmallVector<Value *, 4> Worklist;
SmallPtrSet<Value *, 4> Visited;
Worklist.push_back(II->getOperand(0));
while (!Worklist.empty()) {
Value *Cond = Worklist.pop_back_val();
if (!Visited.insert(Cond).second)
continue;
if (Visited.size() > MaxCondsPerBranch)
break;
Value *Op0, *Op1;
if (match(Cond, m_LogicalAnd(m_Value(Op0), m_Value(Op1)))) {
Worklist.push_back(Op1);
Worklist.push_back(Op0);
}
SmallVector<Value *, 4> Values;
Values.push_back(Cond);
if (auto *Cmp = dyn_cast<CmpInst>(Cond))
collectCmpOps(Cmp, Values);
for (Value *V : Values) {
if (shouldRename(V)) {
auto *PA = new PredicateAssume(V, II, Cond);
addInfoFor(OpsToRename, V, PA);
}
}
}
}
// Process a block terminating branch, and place relevant operations to be
// renamed into OpsToRename.
void PredicateInfoBuilder::processBranch(
BranchInst *BI, BasicBlock *BranchBB,
SmallVectorImpl<Value *> &OpsToRename) {
BasicBlock *FirstBB = BI->getSuccessor(0);
BasicBlock *SecondBB = BI->getSuccessor(1);
for (BasicBlock *Succ : {FirstBB, SecondBB}) {
bool TakenEdge = Succ == FirstBB;
// Don't try to insert on a self-edge. This is mainly because we will
// eliminate during renaming anyway.
if (Succ == BranchBB)
continue;
SmallVector<Value *, 4> Worklist;
SmallPtrSet<Value *, 4> Visited;
Worklist.push_back(BI->getCondition());
while (!Worklist.empty()) {
Value *Cond = Worklist.pop_back_val();
if (!Visited.insert(Cond).second)
continue;
if (Visited.size() > MaxCondsPerBranch)
break;
Value *Op0, *Op1;
if (TakenEdge ? match(Cond, m_LogicalAnd(m_Value(Op0), m_Value(Op1)))
: match(Cond, m_LogicalOr(m_Value(Op0), m_Value(Op1)))) {
Worklist.push_back(Op1);
Worklist.push_back(Op0);
}
SmallVector<Value *, 4> Values;
Values.push_back(Cond);
if (auto *Cmp = dyn_cast<CmpInst>(Cond))
collectCmpOps(Cmp, Values);
for (Value *V : Values) {
if (shouldRename(V)) {
PredicateBase *PB =
new PredicateBranch(V, BranchBB, Succ, Cond, TakenEdge);
addInfoFor(OpsToRename, V, PB);
if (!Succ->getSinglePredecessor())
EdgeUsesOnly.insert({BranchBB, Succ});
}
}
}
}
}
// Process a block terminating switch, and place relevant operations to be
// renamed into OpsToRename.
void PredicateInfoBuilder::processSwitch(
SwitchInst *SI, BasicBlock *BranchBB,
SmallVectorImpl<Value *> &OpsToRename) {
Value *Op = SI->getCondition();
if ((!isa<Instruction>(Op) && !isa<Argument>(Op)) || Op->hasOneUse())
return;
// Remember how many outgoing edges there are to every successor.
SmallDenseMap<BasicBlock *, unsigned, 16> SwitchEdges;
for (unsigned i = 0, e = SI->getNumSuccessors(); i != e; ++i) {
BasicBlock *TargetBlock = SI->getSuccessor(i);
++SwitchEdges[TargetBlock];
}
// Now propagate info for each case value
for (auto C : SI->cases()) {
BasicBlock *TargetBlock = C.getCaseSuccessor();
if (SwitchEdges.lookup(TargetBlock) == 1) {
PredicateSwitch *PS = new PredicateSwitch(
Op, SI->getParent(), TargetBlock, C.getCaseValue(), SI);
addInfoFor(OpsToRename, Op, PS);
if (!TargetBlock->getSinglePredecessor())
EdgeUsesOnly.insert({BranchBB, TargetBlock});
}
}
}
// Build predicate info for our function
void PredicateInfoBuilder::buildPredicateInfo() {
DT.updateDFSNumbers();
// Collect operands to rename from all conditional branch terminators, as well
// as assume statements.
SmallVector<Value *, 8> OpsToRename;
for (auto DTN : depth_first(DT.getRootNode())) {
BasicBlock *BranchBB = DTN->getBlock();
if (auto *BI = dyn_cast<BranchInst>(BranchBB->getTerminator())) {
if (!BI->isConditional())
continue;
// Can't insert conditional information if they all go to the same place.
if (BI->getSuccessor(0) == BI->getSuccessor(1))
continue;
processBranch(BI, BranchBB, OpsToRename);
} else if (auto *SI = dyn_cast<SwitchInst>(BranchBB->getTerminator())) {
processSwitch(SI, BranchBB, OpsToRename);
}
}
for (auto &Assume : AC.assumptions()) {
if (auto *II = dyn_cast_or_null<IntrinsicInst>(Assume))
if (DT.isReachableFromEntry(II->getParent()))
processAssume(II, II->getParent(), OpsToRename);
}
// Now rename all our operations.
renameUses(OpsToRename);
}
// Given the renaming stack, make all the operands currently on the stack real
// by inserting them into the IR. Return the last operation's value.
Value *PredicateInfoBuilder::materializeStack(unsigned int &Counter,
ValueDFSStack &RenameStack,
Value *OrigOp) {
// Find the first thing we have to materialize
auto RevIter = RenameStack.rbegin();
for (; RevIter != RenameStack.rend(); ++RevIter)
if (RevIter->Def)
break;
size_t Start = RevIter - RenameStack.rbegin();
// The maximum number of things we should be trying to materialize at once
// right now is 4, depending on if we had an assume, a branch, and both used
// and of conditions.
for (auto RenameIter = RenameStack.end() - Start;
RenameIter != RenameStack.end(); ++RenameIter) {
auto *Op =
RenameIter == RenameStack.begin() ? OrigOp : (RenameIter - 1)->Def;
ValueDFS &Result = *RenameIter;
auto *ValInfo = Result.PInfo;
ValInfo->RenamedOp = (RenameStack.end() - Start) == RenameStack.begin()
? OrigOp
: (RenameStack.end() - Start - 1)->Def;
// For edge predicates, we can just place the operand in the block before
// the terminator. For assume, we have to place it right before the assume
// to ensure we dominate all of our uses. Always insert right before the
// relevant instruction (terminator, assume), so that we insert in proper
// order in the case of multiple predicateinfo in the same block.
// The number of named values is used to detect if a new declaration was
// added. If so, that declaration is tracked so that it can be removed when
// the analysis is done. The corner case were a new declaration results in
// a name clash and the old name being renamed is not considered as that
// represents an invalid module.
if (isa<PredicateWithEdge>(ValInfo)) {
IRBuilder<> B(getBranchTerminator(ValInfo));
auto NumDecls = F.getParent()->getNumNamedValues();
Function *IF = Intrinsic::getDeclaration(
F.getParent(), Intrinsic::ssa_copy, Op->getType());
if (NumDecls != F.getParent()->getNumNamedValues())
PI.CreatedDeclarations.insert(IF);
CallInst *PIC =
B.CreateCall(IF, Op, Op->getName() + "." + Twine(Counter++));
PI.PredicateMap.insert({PIC, ValInfo});
Result.Def = PIC;
} else {
auto *PAssume = dyn_cast<PredicateAssume>(ValInfo);
assert(PAssume &&
"Should not have gotten here without it being an assume");
// Insert the predicate directly after the assume. While it also holds
// directly before it, assume(i1 true) is not a useful fact.
IRBuilder<> B(PAssume->AssumeInst->getNextNode());
auto NumDecls = F.getParent()->getNumNamedValues();
Function *IF = Intrinsic::getDeclaration(
F.getParent(), Intrinsic::ssa_copy, Op->getType());
if (NumDecls != F.getParent()->getNumNamedValues())
PI.CreatedDeclarations.insert(IF);
CallInst *PIC = B.CreateCall(IF, Op);
PI.PredicateMap.insert({PIC, ValInfo});
Result.Def = PIC;
}
}
return RenameStack.back().Def;
}
// Instead of the standard SSA renaming algorithm, which is O(Number of
// instructions), and walks the entire dominator tree, we walk only the defs +
// uses. The standard SSA renaming algorithm does not really rely on the
// dominator tree except to order the stack push/pops of the renaming stacks, so
// that defs end up getting pushed before hitting the correct uses. This does
// not require the dominator tree, only the *order* of the dominator tree. The
// complete and correct ordering of the defs and uses, in dominator tree is
// contained in the DFS numbering of the dominator tree. So we sort the defs and
// uses into the DFS ordering, and then just use the renaming stack as per
// normal, pushing when we hit a def (which is a predicateinfo instruction),
// popping when we are out of the dfs scope for that def, and replacing any uses
// with top of stack if it exists. In order to handle liveness without
// propagating liveness info, we don't actually insert the predicateinfo
// instruction def until we see a use that it would dominate. Once we see such
// a use, we materialize the predicateinfo instruction in the right place and
// use it.
//
// TODO: Use this algorithm to perform fast single-variable renaming in
// promotememtoreg and memoryssa.
void PredicateInfoBuilder::renameUses(SmallVectorImpl<Value *> &OpsToRename) {
ValueDFS_Compare Compare(DT);
// Compute liveness, and rename in O(uses) per Op.
for (auto *Op : OpsToRename) {
LLVM_DEBUG(dbgs() << "Visiting " << *Op << "\n");
unsigned Counter = 0;
SmallVector<ValueDFS, 16> OrderedUses;
const auto &ValueInfo = getValueInfo(Op);
// Insert the possible copies into the def/use list.
// They will become real copies if we find a real use for them, and never
// created otherwise.
for (auto &PossibleCopy : ValueInfo.Infos) {
ValueDFS VD;
// Determine where we are going to place the copy by the copy type.
// The predicate info for branches always come first, they will get
// materialized in the split block at the top of the block.
// The predicate info for assumes will be somewhere in the middle,
// it will get materialized in front of the assume.
if (const auto *PAssume = dyn_cast<PredicateAssume>(PossibleCopy)) {
VD.LocalNum = LN_Middle;
DomTreeNode *DomNode = DT.getNode(PAssume->AssumeInst->getParent());
if (!DomNode)
continue;
VD.DFSIn = DomNode->getDFSNumIn();
VD.DFSOut = DomNode->getDFSNumOut();
VD.PInfo = PossibleCopy;
OrderedUses.push_back(VD);
} else if (isa<PredicateWithEdge>(PossibleCopy)) {
// If we can only do phi uses, we treat it like it's in the branch
// block, and handle it specially. We know that it goes last, and only
// dominate phi uses.
auto BlockEdge = getBlockEdge(PossibleCopy);
if (EdgeUsesOnly.count(BlockEdge)) {
VD.LocalNum = LN_Last;
auto *DomNode = DT.getNode(BlockEdge.first);
if (DomNode) {
VD.DFSIn = DomNode->getDFSNumIn();
VD.DFSOut = DomNode->getDFSNumOut();
VD.PInfo = PossibleCopy;
VD.EdgeOnly = true;
OrderedUses.push_back(VD);
}
} else {
// Otherwise, we are in the split block (even though we perform
// insertion in the branch block).
// Insert a possible copy at the split block and before the branch.
VD.LocalNum = LN_First;
auto *DomNode = DT.getNode(BlockEdge.second);
if (DomNode) {
VD.DFSIn = DomNode->getDFSNumIn();
VD.DFSOut = DomNode->getDFSNumOut();
VD.PInfo = PossibleCopy;
OrderedUses.push_back(VD);
}
}
}
}
convertUsesToDFSOrdered(Op, OrderedUses);
// Here we require a stable sort because we do not bother to try to
// assign an order to the operands the uses represent. Thus, two
// uses in the same instruction do not have a strict sort order
// currently and will be considered equal. We could get rid of the
// stable sort by creating one if we wanted.
llvm::stable_sort(OrderedUses, Compare);
SmallVector<ValueDFS, 8> RenameStack;
// For each use, sorted into dfs order, push values and replaces uses with
// top of stack, which will represent the reaching def.
for (auto &VD : OrderedUses) {
// We currently do not materialize copy over copy, but we should decide if
// we want to.
bool PossibleCopy = VD.PInfo != nullptr;
if (RenameStack.empty()) {
LLVM_DEBUG(dbgs() << "Rename Stack is empty\n");
} else {
LLVM_DEBUG(dbgs() << "Rename Stack Top DFS numbers are ("
<< RenameStack.back().DFSIn << ","
<< RenameStack.back().DFSOut << ")\n");
}
LLVM_DEBUG(dbgs() << "Current DFS numbers are (" << VD.DFSIn << ","
<< VD.DFSOut << ")\n");
bool ShouldPush = (VD.Def || PossibleCopy);
bool OutOfScope = !stackIsInScope(RenameStack, VD);
if (OutOfScope || ShouldPush) {
// Sync to our current scope.
popStackUntilDFSScope(RenameStack, VD);
if (ShouldPush) {
RenameStack.push_back(VD);
}
}
// If we get to this point, and the stack is empty we must have a use
// with no renaming needed, just skip it.
if (RenameStack.empty())
continue;
// Skip values, only want to rename the uses
if (VD.Def || PossibleCopy)
continue;
if (!DebugCounter::shouldExecute(RenameCounter)) {
LLVM_DEBUG(dbgs() << "Skipping execution due to debug counter\n");
continue;
}
ValueDFS &Result = RenameStack.back();
// If the possible copy dominates something, materialize our stack up to
// this point. This ensures every comparison that affects our operation
// ends up with predicateinfo.
if (!Result.Def)
Result.Def = materializeStack(Counter, RenameStack, Op);
LLVM_DEBUG(dbgs() << "Found replacement " << *Result.Def << " for "
<< *VD.U->get() << " in " << *(VD.U->getUser())
<< "\n");
assert(DT.dominates(cast<Instruction>(Result.Def), *VD.U) &&
"Predicateinfo def should have dominated this use");
VD.U->set(Result.Def);
}
}
}
PredicateInfoBuilder::ValueInfo &
PredicateInfoBuilder::getOrCreateValueInfo(Value *Operand) {
auto OIN = ValueInfoNums.find(Operand);
if (OIN == ValueInfoNums.end()) {
// This will grow it
ValueInfos.resize(ValueInfos.size() + 1);
// This will use the new size and give us a 0 based number of the info
auto InsertResult = ValueInfoNums.insert({Operand, ValueInfos.size() - 1});
assert(InsertResult.second && "Value info number already existed?");
return ValueInfos[InsertResult.first->second];
}
return ValueInfos[OIN->second];
}
const PredicateInfoBuilder::ValueInfo &
PredicateInfoBuilder::getValueInfo(Value *Operand) const {
auto OINI = ValueInfoNums.lookup(Operand);
assert(OINI != 0 && "Operand was not really in the Value Info Numbers");
assert(OINI < ValueInfos.size() &&
"Value Info Number greater than size of Value Info Table");
return ValueInfos[OINI];
}
PredicateInfo::PredicateInfo(Function &F, DominatorTree &DT,
AssumptionCache &AC)
: F(F) {
PredicateInfoBuilder Builder(*this, F, DT, AC);
Builder.buildPredicateInfo();
}
// Remove all declarations we created . The PredicateInfo consumers are
// responsible for remove the ssa_copy calls created.
PredicateInfo::~PredicateInfo() {
// Collect function pointers in set first, as SmallSet uses a SmallVector
// internally and we have to remove the asserting value handles first.
SmallPtrSet<Function *, 20> FunctionPtrs;
for (auto &F : CreatedDeclarations)
FunctionPtrs.insert(&*F);
CreatedDeclarations.clear();
for (Function *F : FunctionPtrs) {
assert(F->user_begin() == F->user_end() &&
"PredicateInfo consumer did not remove all SSA copies.");
F->eraseFromParent();
}
}
Optional<PredicateConstraint> PredicateBase::getConstraint() const {
switch (Type) {
case PT_Assume:
case PT_Branch: {
bool TrueEdge = true;
if (auto *PBranch = dyn_cast<PredicateBranch>(this))
TrueEdge = PBranch->TrueEdge;
if (Condition == RenamedOp) {
return {{CmpInst::ICMP_EQ,
TrueEdge ? ConstantInt::getTrue(Condition->getType())
: ConstantInt::getFalse(Condition->getType())}};
}
CmpInst *Cmp = dyn_cast<CmpInst>(Condition);
if (!Cmp) {
// TODO: Make this an assertion once RenamedOp is fully accurate.
return None;
}
CmpInst::Predicate Pred;
Value *OtherOp;
if (Cmp->getOperand(0) == RenamedOp) {
Pred = Cmp->getPredicate();
OtherOp = Cmp->getOperand(1);
} else if (Cmp->getOperand(1) == RenamedOp) {
Pred = Cmp->getSwappedPredicate();
OtherOp = Cmp->getOperand(0);
} else {
// TODO: Make this an assertion once RenamedOp is fully accurate.
return None;
}
// Invert predicate along false edge.
if (!TrueEdge)
Pred = CmpInst::getInversePredicate(Pred);
return {{Pred, OtherOp}};
}
case PT_Switch:
if (Condition != RenamedOp) {
// TODO: Make this an assertion once RenamedOp is fully accurate.
return None;
}
return {{CmpInst::ICMP_EQ, cast<PredicateSwitch>(this)->CaseValue}};
}
llvm_unreachable("Unknown predicate type");
}
void PredicateInfo::verifyPredicateInfo() const {}
char PredicateInfoPrinterLegacyPass::ID = 0;
PredicateInfoPrinterLegacyPass::PredicateInfoPrinterLegacyPass()
: FunctionPass(ID) {
initializePredicateInfoPrinterLegacyPassPass(
*PassRegistry::getPassRegistry());
}
void PredicateInfoPrinterLegacyPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequiredTransitive<DominatorTreeWrapperPass>();
AU.addRequired<AssumptionCacheTracker>();
}
// Replace ssa_copy calls created by PredicateInfo with their operand.
static void replaceCreatedSSACopys(PredicateInfo &PredInfo, Function &F) {
for (Instruction &Inst : llvm::make_early_inc_range(instructions(F))) {
const auto *PI = PredInfo.getPredicateInfoFor(&Inst);
auto *II = dyn_cast<IntrinsicInst>(&Inst);
if (!PI || !II || II->getIntrinsicID() != Intrinsic::ssa_copy)
continue;
Inst.replaceAllUsesWith(II->getOperand(0));
Inst.eraseFromParent();
}
}
bool PredicateInfoPrinterLegacyPass::runOnFunction(Function &F) {
auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
auto PredInfo = std::make_unique<PredicateInfo>(F, DT, AC);
PredInfo->print(dbgs());
if (VerifyPredicateInfo)
PredInfo->verifyPredicateInfo();
replaceCreatedSSACopys(*PredInfo, F);
return false;
}
PreservedAnalyses PredicateInfoPrinterPass::run(Function &F,
FunctionAnalysisManager &AM) {
auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
auto &AC = AM.getResult<AssumptionAnalysis>(F);
OS << "PredicateInfo for function: " << F.getName() << "\n";
auto PredInfo = std::make_unique<PredicateInfo>(F, DT, AC);
PredInfo->print(OS);
replaceCreatedSSACopys(*PredInfo, F);
return PreservedAnalyses::all();
}
/// An assembly annotator class to print PredicateInfo information in
/// comments.
class PredicateInfoAnnotatedWriter : public AssemblyAnnotationWriter {
friend class PredicateInfo;
const PredicateInfo *PredInfo;
public:
PredicateInfoAnnotatedWriter(const PredicateInfo *M) : PredInfo(M) {}
void emitBasicBlockStartAnnot(const BasicBlock *BB,
formatted_raw_ostream &OS) override {}
void emitInstructionAnnot(const Instruction *I,
formatted_raw_ostream &OS) override {
if (const auto *PI = PredInfo->getPredicateInfoFor(I)) {
OS << "; Has predicate info\n";
if (const auto *PB = dyn_cast<PredicateBranch>(PI)) {
OS << "; branch predicate info { TrueEdge: " << PB->TrueEdge
<< " Comparison:" << *PB->Condition << " Edge: [";
PB->From->printAsOperand(OS);
OS << ",";
PB->To->printAsOperand(OS);
OS << "]";
} else if (const auto *PS = dyn_cast<PredicateSwitch>(PI)) {
OS << "; switch predicate info { CaseValue: " << *PS->CaseValue
<< " Switch:" << *PS->Switch << " Edge: [";
PS->From->printAsOperand(OS);
OS << ",";
PS->To->printAsOperand(OS);
OS << "]";
} else if (const auto *PA = dyn_cast<PredicateAssume>(PI)) {
OS << "; assume predicate info {"
<< " Comparison:" << *PA->Condition;
}
OS << ", RenamedOp: ";
PI->RenamedOp->printAsOperand(OS, false);
OS << " }\n";
}
}
};
void PredicateInfo::print(raw_ostream &OS) const {
PredicateInfoAnnotatedWriter Writer(this);
F.print(OS, &Writer);
}
void PredicateInfo::dump() const {
PredicateInfoAnnotatedWriter Writer(this);
F.print(dbgs(), &Writer);
}
PreservedAnalyses PredicateInfoVerifierPass::run(Function &F,
FunctionAnalysisManager &AM) {
auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
auto &AC = AM.getResult<AssumptionAnalysis>(F);
std::make_unique<PredicateInfo>(F, DT, AC)->verifyPredicateInfo();
return PreservedAnalyses::all();
}
}
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