[llvm] cec9e73 - [rs4gc] Simplify code by cloning existing instructions when inserting base chain [NFC]
Philip Reames via llvm-commits
llvm-commits at lists.llvm.org
Tue Mar 16 13:16:27 PDT 2021
Author: Philip Reames
Date: 2021-03-16T13:10:32-07:00
New Revision: cec9e7352bebe06681a9627f3fc08228129b7681
URL: https://github.com/llvm/llvm-project/commit/cec9e7352bebe06681a9627f3fc08228129b7681
DIFF: https://github.com/llvm/llvm-project/commit/cec9e7352bebe06681a9627f3fc08228129b7681.diff
LOG: [rs4gc] Simplify code by cloning existing instructions when inserting base chain [NFC]
Previously we created a new node, then filled in the pieces. Now, we clone the existing node, then change the respective fields. The only change in handling is with phis since we have to handle multiple incoming edges from the same block a bit differently.
Differential Revision: https://reviews.llvm.org/D98316
Added:
Modified:
llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
index 755ebb881622..fdc1c483cb2a 100644
--- a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
+++ b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
@@ -1057,40 +1057,23 @@ static Value *findBasePointer(Value *I, DefiningValueMapTy &Cache) {
if (!State.isConflict())
continue;
- /// Create and insert a new instruction which will represent the base of
- /// the given instruction 'I'.
- auto MakeBaseInstPlaceholder = [](Instruction *I) -> Instruction* {
+ auto getMangledName = [](Instruction *I) -> std::string {
if (isa<PHINode>(I)) {
- BasicBlock *BB = I->getParent();
- int NumPreds = pred_size(BB);
- assert(NumPreds > 0 && "how did we reach here");
- std::string Name = suffixed_name_or(I, ".base", "base_phi");
- return PHINode::Create(I->getType(), NumPreds, Name, I);
- } else if (SelectInst *SI = dyn_cast<SelectInst>(I)) {
- // The undef will be replaced later
- UndefValue *Undef = UndefValue::get(SI->getType());
- std::string Name = suffixed_name_or(I, ".base", "base_select");
- return SelectInst::Create(SI->getCondition(), Undef, Undef, Name, SI);
- } else if (auto *EE = dyn_cast<ExtractElementInst>(I)) {
- UndefValue *Undef = UndefValue::get(EE->getVectorOperand()->getType());
- std::string Name = suffixed_name_or(I, ".base", "base_ee");
- return ExtractElementInst::Create(Undef, EE->getIndexOperand(), Name,
- EE);
- } else if (auto *IE = dyn_cast<InsertElementInst>(I)) {
- UndefValue *VecUndef = UndefValue::get(IE->getOperand(0)->getType());
- UndefValue *ScalarUndef = UndefValue::get(IE->getOperand(1)->getType());
- std::string Name = suffixed_name_or(I, ".base", "base_ie");
- return InsertElementInst::Create(VecUndef, ScalarUndef,
- IE->getOperand(2), Name, IE);
+ return suffixed_name_or(I, ".base", "base_phi");
+ } else if (isa<SelectInst>(I)) {
+ return suffixed_name_or(I, ".base", "base_select");
+ } else if (isa<ExtractElementInst>(I)) {
+ return suffixed_name_or(I, ".base", "base_ee");
+ } else if (isa<InsertElementInst>(I)) {
+ return suffixed_name_or(I, ".base", "base_ie");
} else {
- auto *SV = cast<ShuffleVectorInst>(I);
- UndefValue *VecUndef = UndefValue::get(SV->getOperand(0)->getType());
- std::string Name = suffixed_name_or(I, ".base", "base_sv");
- return new ShuffleVectorInst(VecUndef, VecUndef, SV->getShuffleMask(),
- Name, SV);
+ return suffixed_name_or(I, ".base", "base_sv");
}
};
- Instruction *BaseInst = MakeBaseInstPlaceholder(I);
+
+ Instruction *BaseInst = I->clone();
+ BaseInst->insertBefore(I);
+ BaseInst->setName(getMangledName(I));
// Add metadata marking this as a base value
BaseInst->setMetadata("is_base_value", MDNode::get(I->getContext(), {}));
States[I] = BDVState(I, BDVState::Conflict, BaseInst);
@@ -1145,26 +1128,21 @@ static Value *findBasePointer(Value *I, DefiningValueMapTy &Cache) {
if (PHINode *BasePHI = dyn_cast<PHINode>(State.getBaseValue())) {
PHINode *PN = cast<PHINode>(BDV);
- unsigned NumPHIValues = PN->getNumIncomingValues();
+ const unsigned NumPHIValues = PN->getNumIncomingValues();
+
+ // The IR verifier requires phi nodes with multiple entries from the
+ // same basic block to have the same incoming value for each of those
+ // entries. Since we're inserting bitcasts in the loop, make sure we
+ // do so at least once per incoming block.
+ DenseMap<BasicBlock *, Value*> BlockToValue;
for (unsigned i = 0; i < NumPHIValues; i++) {
Value *InVal = PN->getIncomingValue(i);
BasicBlock *InBB = PN->getIncomingBlock(i);
-
- // If we've already seen InBB, add the same incoming value
- // we added for it earlier. The IR verifier requires phi
- // nodes with multiple entries from the same basic block
- // to have the same incoming value for each of those
- // entries. If we don't do this check here and basephi
- // has a
diff erent type than base, we'll end up adding two
- // bitcasts (and hence two distinct values) as incoming
- // values for the same basic block.
-
- int BlockIndex = BasePHI->getBasicBlockIndex(InBB);
- if (BlockIndex != -1) {
- Value *OldBase = BasePHI->getIncomingValue(BlockIndex);
- BasePHI->addIncoming(OldBase, InBB);
-
+ if (!BlockToValue.count(InBB))
+ BlockToValue[InBB] = getBaseForInput(InVal, InBB->getTerminator());
+ else {
#ifndef NDEBUG
+ Value *OldBase = BlockToValue[InBB];
Value *Base = getBaseForInput(InVal, nullptr);
// In essence this assert states: the only way two values
// incoming from the same basic block may be
diff erent is by
@@ -1175,16 +1153,10 @@ static Value *findBasePointer(Value *I, DefiningValueMapTy &Cache) {
assert(Base->stripPointerCasts() == OldBase->stripPointerCasts() &&
"Sanity -- findBaseOrBDV should be pure!");
#endif
- continue;
}
-
- // Find the instruction which produces the base for each input. We may
- // need to insert a bitcast in the incoming block.
- // TODO: Need to split critical edges if insertion is needed
- Value *Base = getBaseForInput(InVal, InBB->getTerminator());
- BasePHI->addIncoming(Base, InBB);
+ Value *Base = BlockToValue[InBB];
+ BasePHI->setIncomingValue(i, Base);
}
- assert(BasePHI->getNumIncomingValues() == NumPHIValues);
} else if (SelectInst *BaseSI =
dyn_cast<SelectInst>(State.getBaseValue())) {
SelectInst *SI = cast<SelectInst>(BDV);
@@ -1219,6 +1191,11 @@ static Value *findBasePointer(Value *I, DefiningValueMapTy &Cache) {
UpdateOperand(0); // vector operand
if (!BdvSV->isZeroEltSplat())
UpdateOperand(1); // vector operand
+ else {
+ // Never read, so just use undef
+ Value *InVal = BdvSV->getOperand(1);
+ BaseSV->setOperand(1, UndefValue::get(InVal->getType()));
+ }
}
}
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