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Exploit dereferenceable_or_null attribute in LICM pass

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Summary:
Allow hoisting of loads from values marked with dereferenceable_or_null
attribute. For values marked with the attribute perform
context-sensitive analysis to determine whether it's known-non-null or
not.

Patch by Artur Pilipenko!

Reviewers: hfinkel, sanjoy, reames

Reviewed By: reames

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D9253

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237593 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das
2015-05-18 18:07:00 +00:00
parent 9962fd0e2e
commit 0799eb1140
5 changed files with 237 additions and 43 deletions
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28
lib/Transforms/Scalar/LICM.cpp
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@@ -82,6 +82,7 @@ static bool isGuaranteedToExecute(const Instruction &Inst,
const LICMSafetyInfo *SafetyInfo);
static bool isSafeToExecuteUnconditionally(const Instruction &Inst,
const DominatorTree *DT,
const TargetLibraryInfo *TLI,
const Loop *CurLoop,
const LICMSafetyInfo *SafetyInfo);
static bool pointerInvalidatedByLoop(Value *V, uint64_t Size,
@@ -92,8 +93,8 @@ static Instruction *CloneInstructionInExitBlock(const Instruction &I,
PHINode &PN,
const LoopInfo *LI);
static bool canSinkOrHoistInst(Instruction &I, AliasAnalysis *AA,
DominatorTree *DT, Loop *CurLoop,
AliasSetTracker *CurAST,
DominatorTree *DT, TargetLibraryInfo *TLI,
Loop *CurLoop, AliasSetTracker *CurAST,
LICMSafetyInfo *SafetyInfo);
namespace {
@@ -337,7 +338,7 @@ bool llvm::sinkRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
// operands of the instruction are loop invariant.
//
if (isNotUsedInLoop(I, CurLoop) &&
canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo)) {
canSinkOrHoistInst(I, AA, DT, TLI, CurLoop, CurAST, SafetyInfo)) {
++II;
Changed |= sink(I, LI, DT, CurLoop, CurAST);
}
@@ -386,8 +387,8 @@ bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
// is safe to hoist the instruction.
//
if (CurLoop->hasLoopInvariantOperands(&I) &&
canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo) &&
isSafeToExecuteUnconditionally(I, DT, CurLoop, SafetyInfo))
canSinkOrHoistInst(I, AA, DT, TLI, CurLoop, CurAST, SafetyInfo) &&
isSafeToExecuteUnconditionally(I, DT, TLI, CurLoop, SafetyInfo))
Changed |= hoist(I, CurLoop->getLoopPreheader());
}
@@ -425,8 +426,8 @@ void llvm::computeLICMSafetyInfo(LICMSafetyInfo * SafetyInfo, Loop * CurLoop) {
/// instruction.
///
bool canSinkOrHoistInst(Instruction &I, AliasAnalysis *AA, DominatorTree *DT,
Loop *CurLoop, AliasSetTracker *CurAST,
LICMSafetyInfo *SafetyInfo) {
TargetLibraryInfo *TLI, Loop *CurLoop,
AliasSetTracker *CurAST, LICMSafetyInfo *SafetyInfo) {
// Loads have extra constraints we have to verify before we can hoist them.
if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
if (!LI->isUnordered())
@@ -486,7 +487,7 @@ bool canSinkOrHoistInst(Instruction &I, AliasAnalysis *AA, DominatorTree *DT,
!isa<InsertValueInst>(I))
return false;
return isSafeToExecuteUnconditionally(I, DT, CurLoop, SafetyInfo);
return isSafeToExecuteUnconditionally(I, DT, TLI, CurLoop, SafetyInfo);
}
/// Returns true if a PHINode is a trivially replaceable with an
@@ -639,15 +640,16 @@ static bool hoist(Instruction &I, BasicBlock *Preheader) {
return true;
}
/// Only sink or hoist an instruction if it is not a trapping instruction
/// Only sink or hoist an instruction if it is not a trapping instruction,
/// or if the instruction is known not to trap when moved to the preheader.
/// or if it is a trapping instruction and is guaranteed to execute.
///
static bool isSafeToExecuteUnconditionally(const Instruction &Inst,
static bool isSafeToExecuteUnconditionally(const Instruction &Inst,
const DominatorTree *DT,
const TargetLibraryInfo *TLI,
const Loop *CurLoop,
const LICMSafetyInfo *SafetyInfo) {
// If it is not a trapping instruction, it is always safe to hoist.
if (isSafeToSpeculativelyExecute(&Inst))
const Instruction *CtxI = CurLoop->getLoopPreheader()->getTerminator();
if (isSafeToSpeculativelyExecute(&Inst, CtxI, DT, TLI))
return true;
return isGuaranteedToExecute(Inst, DT, CurLoop, SafetyInfo);