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[JumpThreading][NFC] Rename LoadInst variables 

Summary:
The JumpThreading pass has several locations where to the variable name LI
refers to a LoadInst type. This is confusing and inhibits the ability to use
LI for LoopInfo as a member of the JumpThreading class. Minor formatting
and comments were also altered to reflect this change.

Reviewers: dberlin, kuba, spop, sebpop

Reviewed by: sebpop

Subscribers: sebpop, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D42601

llvm-svn: 323695
This commit is contained in:
Brian M. Rzycki 2018-01-29 21:29:44 +00:00
parent 6f73cf45df
commit 994e889022
1 changed files with 46 additions and 43 deletions
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89
llvm/lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -1149,8 +1149,8 @@ bool JumpThreadingPass::ProcessBlock(BasicBlock *BB) {
// TODO: There are other places where load PRE would be profitable, such as
// more complex comparisons.
if (LoadInst *LI = dyn_cast<LoadInst>(SimplifyValue))
if (SimplifyPartiallyRedundantLoad(LI))
if (LoadInst *LoadI = dyn_cast<LoadInst>(SimplifyValue))
if (SimplifyPartiallyRedundantLoad(LoadI))
return true;
// Before threading, try to propagate profile data backwards:
@ -1229,17 +1229,17 @@ static bool isOpDefinedInBlock(Value *Op, BasicBlock *BB) {
return false;
}
/// SimplifyPartiallyRedundantLoad - If LI is an obviously partially redundant
/// load instruction, eliminate it by replacing it with a PHI node. This is an
/// important optimization that encourages jump threading, and needs to be run
/// interlaced with other jump threading tasks.
bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
/// SimplifyPartiallyRedundantLoad - If LoadI is an obviously partially
/// redundant load instruction, eliminate it by replacing it with a PHI node.
/// This is an important optimization that encourages jump threading, and needs
/// to be run interlaced with other jump threading tasks.
bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LoadI) {
// Don't hack volatile and ordered loads.
if (!LI->isUnordered()) return false;
if (!LoadI->isUnordered()) return false;
// If the load is defined in a block with exactly one predecessor, it can't be
// partially redundant.
BasicBlock *LoadBB = LI->getParent();
BasicBlock *LoadBB = LoadI->getParent();
if (LoadBB->getSinglePredecessor())
return false;
@ -1249,7 +1249,7 @@ bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
if (LoadBB->isEHPad())
return false;
Value *LoadedPtr = LI->getOperand(0);
Value *LoadedPtr = LoadI->getOperand(0);
// If the loaded operand is defined in the LoadBB and its not a phi,
// it can't be available in predecessors.
@ -1258,26 +1258,27 @@ bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
// Scan a few instructions up from the load, to see if it is obviously live at
// the entry to its block.
BasicBlock::iterator BBIt(LI);
BasicBlock::iterator BBIt(LoadI);
bool IsLoadCSE;
if (Value *AvailableVal = FindAvailableLoadedValue(
LI, LoadBB, BBIt, DefMaxInstsToScan, AA, &IsLoadCSE)) {
LoadI, LoadBB, BBIt, DefMaxInstsToScan, AA, &IsLoadCSE)) {
// If the value of the load is locally available within the block, just use
// it. This frequently occurs for reg2mem'd allocas.
if (IsLoadCSE) {
LoadInst *NLI = cast<LoadInst>(AvailableVal);
combineMetadataForCSE(NLI, LI);
LoadInst *NLoadI = cast<LoadInst>(AvailableVal);
combineMetadataForCSE(NLoadI, LoadI);
};
// If the returned value is the load itself, replace with an undef. This can
// only happen in dead loops.
if (AvailableVal == LI) AvailableVal = UndefValue::get(LI->getType());
if (AvailableVal->getType() != LI->getType())
AvailableVal =
CastInst::CreateBitOrPointerCast(AvailableVal, LI->getType(), "", LI);
LI->replaceAllUsesWith(AvailableVal);
LI->eraseFromParent();
if (AvailableVal == LoadI)
AvailableVal = UndefValue::get(LoadI->getType());
if (AvailableVal->getType() != LoadI->getType())
AvailableVal = CastInst::CreateBitOrPointerCast(
AvailableVal, LoadI->getType(), "", LoadI);
LoadI->replaceAllUsesWith(AvailableVal);
LoadI->eraseFromParent();
return true;
}
@ -1290,7 +1291,7 @@ bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
// If all of the loads and stores that feed the value have the same AA tags,
// then we can propagate them onto any newly inserted loads.
AAMDNodes AATags;
LI->getAAMetadata(AATags);
LoadI->getAAMetadata(AATags);
SmallPtrSet<BasicBlock*, 8> PredsScanned;
@ -1312,13 +1313,14 @@ bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
Value *PredAvailable = nullptr;
// NOTE: We don't CSE load that is volatile or anything stronger than
// unordered, that should have been checked when we entered the function.
assert(LI->isUnordered() && "Attempting to CSE volatile or atomic loads");
assert(LoadI->isUnordered() &&
"Attempting to CSE volatile or atomic loads");
// If this is a load on a phi pointer, phi-translate it and search
// for available load/store to the pointer in predecessors.
Value *Ptr = LoadedPtr->DoPHITranslation(LoadBB, PredBB);
PredAvailable = FindAvailablePtrLoadStore(
Ptr, LI->getType(), LI->isAtomic(), PredBB, BBIt, DefMaxInstsToScan,
AA, &IsLoadCSE, &NumScanedInst);
Ptr, LoadI->getType(), LoadI->isAtomic(), PredBB, BBIt,
DefMaxInstsToScan, AA, &IsLoadCSE, &NumScanedInst);
// If PredBB has a single predecessor, continue scanning through the
// single precessor.
@ -1329,7 +1331,7 @@ bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
if (SinglePredBB) {
BBIt = SinglePredBB->end();
PredAvailable = FindAvailablePtrLoadStore(
Ptr, LI->getType(), LI->isAtomic(), SinglePredBB, BBIt,
Ptr, LoadI->getType(), LoadI->isAtomic(), SinglePredBB, BBIt,
(DefMaxInstsToScan - NumScanedInst), AA, &IsLoadCSE,
&NumScanedInst);
}
@ -1361,15 +1363,15 @@ bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
// If the value is unavailable in one of predecessors, we will end up
// inserting a new instruction into them. It is only valid if all the
// instructions before LI are guaranteed to pass execution to its successor,
// or if LI is safe to speculate.
// instructions before LoadI are guaranteed to pass execution to its
// successor, or if LoadI is safe to speculate.
// TODO: If this logic becomes more complex, and we will perform PRE insertion
// farther than to a predecessor, we need to reuse the code from GVN's PRE.
// It requires domination tree analysis, so for this simple case it is an
// overkill.
if (PredsScanned.size() != AvailablePreds.size() &&
!isSafeToSpeculativelyExecute(LI))
for (auto I = LoadBB->begin(); &*I != LI; ++I)
!isSafeToSpeculativelyExecute(LoadI))
for (auto I = LoadBB->begin(); &*I != LoadI; ++I)
if (!isGuaranteedToTransferExecutionToSuccessor(&*I))
return false;
@ -1408,11 +1410,12 @@ bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
if (UnavailablePred) {
assert(UnavailablePred->getTerminator()->getNumSuccessors() == 1 &&
"Can't handle critical edge here!");
LoadInst *NewVal = new LoadInst(
LoadedPtr->DoPHITranslation(LoadBB, UnavailablePred),
LI->getName() + ".pr", false, LI->getAlignment(), LI->getOrdering(),
LI->getSyncScopeID(), UnavailablePred->getTerminator());
NewVal->setDebugLoc(LI->getDebugLoc());
LoadInst *NewVal =
new LoadInst(LoadedPtr->DoPHITranslation(LoadBB, UnavailablePred),
LoadI->getName() + ".pr", false, LoadI->getAlignment(),
LoadI->getOrdering(), LoadI->getSyncScopeID(),
UnavailablePred->getTerminator());
NewVal->setDebugLoc(LoadI->getDebugLoc());
if (AATags)
NewVal->setAAMetadata(AATags);
@ -1425,10 +1428,10 @@ bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
// Create a PHI node at the start of the block for the PRE'd load value.
pred_iterator PB = pred_begin(LoadBB), PE = pred_end(LoadBB);
PHINode *PN = PHINode::Create(LI->getType(), std::distance(PB, PE), "",
PHINode *PN = PHINode::Create(LoadI->getType(), std::distance(PB, PE), "",
&LoadBB->front());
PN->takeName(LI);
PN->setDebugLoc(LI->getDebugLoc());
PN->takeName(LoadI);
PN->setDebugLoc(LoadI->getDebugLoc());
// Insert new entries into the PHI for each predecessor. A single block may
// have multiple entries here.
@ -1446,19 +1449,19 @@ bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
// AvailablePreds vector as we go so that all of the PHI entries for this
// predecessor use the same bitcast.
Value *&PredV = I->second;
if (PredV->getType() != LI->getType())
PredV = CastInst::CreateBitOrPointerCast(PredV, LI->getType(), "",
if (PredV->getType() != LoadI->getType())
PredV = CastInst::CreateBitOrPointerCast(PredV, LoadI->getType(), "",
P->getTerminator());
PN->addIncoming(PredV, I->first);
}
for (LoadInst *PredLI : CSELoads) {
combineMetadataForCSE(PredLI, LI);
for (LoadInst *PredLoadI : CSELoads) {
combineMetadataForCSE(PredLoadI, LoadI);
}
LI->replaceAllUsesWith(PN);
LI->eraseFromParent();
LoadI->replaceAllUsesWith(PN);
LoadI->eraseFromParent();
return true;
}