[llvm] d4a38c8 - [DFAJumpThreading] Handle select unfolding when user phi is not a dir… (#109511)
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Tue Sep 24 08:54:40 PDT 2024
Author: Usman Nadeem
Date: 2024-09-24T08:54:36-07:00
New Revision: d4a38c8ff5c993e14c42895b51a47272fb03a857
URL: https://github.com/llvm/llvm-project/commit/d4a38c8ff5c993e14c42895b51a47272fb03a857
DIFF: https://github.com/llvm/llvm-project/commit/d4a38c8ff5c993e14c42895b51a47272fb03a857.diff
LOG: [DFAJumpThreading] Handle select unfolding when user phi is not a dir… (#109511)
…ect successor
Previously the code assumed that the select instruction is defined in a
block that is a direct predecessor of the block where the PHINode uses
it. So, we were hitting an assertion when we tried to access the def
block as an incoming block for the user phi node.
This patch handles that case by using the correct end block and creating
a new phi node that aggregates both the values of the select in that end
block, and then using that new unfolded phi to overwrite the original
user phi node.
Fixes #106083
Change-Id: Ie471994cca232318f74a6e6438efa21e561c2dc0
Added:
Modified:
llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
llvm/test/Transforms/DFAJumpThreading/dfa-jump-threading-transform.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp b/llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
index ef9c264482a640..0e2b5c925a6a7a 100644
--- a/llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
@@ -194,7 +194,6 @@ void unfold(DomTreeUpdater *DTU, LoopInfo *LI, SelectInstToUnfold SIToUnfold,
SelectInst *SI = SIToUnfold.getInst();
PHINode *SIUse = SIToUnfold.getUse();
BasicBlock *StartBlock = SI->getParent();
- BasicBlock *EndBlock = SIUse->getParent();
BranchInst *StartBlockTerm =
dyn_cast<BranchInst>(StartBlock->getTerminator());
@@ -202,6 +201,7 @@ void unfold(DomTreeUpdater *DTU, LoopInfo *LI, SelectInstToUnfold SIToUnfold,
assert(SI->hasOneUse());
if (StartBlockTerm->isUnconditional()) {
+ BasicBlock *EndBlock = StartBlock->getUniqueSuccessor();
// Arbitrarily choose the 'false' side for a new input value to the PHI.
BasicBlock *NewBlock = BasicBlock::Create(
SI->getContext(), Twine(SI->getName(), ".si.unfold.false"),
@@ -223,32 +223,44 @@ void unfold(DomTreeUpdater *DTU, LoopInfo *LI, SelectInstToUnfold SIToUnfold,
NewBlock->getFirstInsertionPt());
NewPhi->addIncoming(SIOp2, StartBlock);
- if (auto *OpSi = dyn_cast<SelectInst>(SIOp1))
- NewSIsToUnfold->push_back(SelectInstToUnfold(OpSi, SIUse));
- if (auto *OpSi = dyn_cast<SelectInst>(SIOp2))
- NewSIsToUnfold->push_back(SelectInstToUnfold(OpSi, NewPhi));
-
- // Update the phi node of SI.
- for (unsigned Idx = 0; Idx < SIUse->getNumIncomingValues(); ++Idx) {
- if (SIUse->getIncomingBlock(Idx) == StartBlock)
- SIUse->setIncomingValue(Idx, SIOp1);
+ // Update any other PHI nodes in EndBlock.
+ for (PHINode &Phi : EndBlock->phis()) {
+ if (SIUse == &Phi)
+ continue;
+ Phi.addIncoming(Phi.getIncomingValueForBlock(StartBlock), NewBlock);
}
- SIUse->addIncoming(NewPhi, NewBlock);
- // Update any other PHI nodes in EndBlock.
- for (auto II = EndBlock->begin(); PHINode *Phi = dyn_cast<PHINode>(II);
- ++II) {
- if (Phi != SIUse)
- Phi->addIncoming(Phi->getIncomingValueForBlock(StartBlock), NewBlock);
+ // Update the phi node of SI, which is its only use.
+ if (EndBlock == SIUse->getParent()) {
+ SIUse->addIncoming(NewPhi, NewBlock);
+ SIUse->replaceUsesOfWith(SI, SIOp1);
+ } else {
+ PHINode *EndPhi = PHINode::Create(SIUse->getType(), pred_size(EndBlock),
+ Twine(SI->getName(), ".si.unfold.phi"),
+ EndBlock->getFirstInsertionPt());
+ for (BasicBlock *Pred : predecessors(EndBlock)) {
+ if (Pred != StartBlock && Pred != NewBlock)
+ EndPhi->addIncoming(EndPhi, Pred);
+ }
+
+ EndPhi->addIncoming(SIOp1, StartBlock);
+ EndPhi->addIncoming(NewPhi, NewBlock);
+ SIUse->replaceUsesOfWith(SI, EndPhi);
+ SIUse = EndPhi;
}
- StartBlockTerm->eraseFromParent();
+ if (auto *OpSi = dyn_cast<SelectInst>(SIOp1))
+ NewSIsToUnfold->push_back(SelectInstToUnfold(OpSi, SIUse));
+ if (auto *OpSi = dyn_cast<SelectInst>(SIOp2))
+ NewSIsToUnfold->push_back(SelectInstToUnfold(OpSi, NewPhi));
// Insert the real conditional branch based on the original condition.
+ StartBlockTerm->eraseFromParent();
BranchInst::Create(EndBlock, NewBlock, SI->getCondition(), StartBlock);
DTU->applyUpdates({{DominatorTree::Insert, StartBlock, EndBlock},
{DominatorTree::Insert, StartBlock, NewBlock}});
} else {
+ BasicBlock *EndBlock = SIUse->getParent();
BasicBlock *NewBlockT = BasicBlock::Create(
SI->getContext(), Twine(SI->getName(), ".si.unfold.true"),
EndBlock->getParent(), EndBlock);
diff --git a/llvm/test/Transforms/DFAJumpThreading/dfa-jump-threading-transform.ll b/llvm/test/Transforms/DFAJumpThreading/dfa-jump-threading-transform.ll
index c38f81d0f046ef..cba1ba8dde768e 100644
--- a/llvm/test/Transforms/DFAJumpThreading/dfa-jump-threading-transform.ll
+++ b/llvm/test/Transforms/DFAJumpThreading/dfa-jump-threading-transform.ll
@@ -300,3 +300,126 @@ define void @self-reference() {
end:
ret void
}
+
+define void @pr106083_invalidBBarg_fold(i1 %cmp1, i1 %cmp2, i1 %not, ptr %d) {
+; CHECK-LABEL: @pr106083_invalidBBarg_fold(
+; CHECK-NEXT: bb:
+; CHECK-NEXT: br i1 [[CMP1:%.*]], label [[BB1:%.*]], label [[SEL_SI_UNFOLD_FALSE:%.*]]
+; CHECK: sel.si.unfold.false:
+; CHECK-NEXT: [[DOTSI_UNFOLD_PHI1:%.*]] = phi i32 [ 1, [[BB:%.*]] ]
+; CHECK-NEXT: br label [[BB1]]
+; CHECK: BB1:
+; CHECK-NEXT: [[I:%.*]] = phi i16 [ 0, [[BB1_BACKEDGE:%.*]] ], [ 0, [[BB]] ], [ 1, [[BB7:%.*]] ], [ 0, [[SEL_SI_UNFOLD_FALSE]] ], [ 1, [[BB7_JT0:%.*]] ]
+; CHECK-NEXT: [[SEL_SI_UNFOLD_PHI:%.*]] = phi i32 [ [[SEL_SI_UNFOLD_PHI]], [[BB1_BACKEDGE]] ], [ [[SEL_SI_UNFOLD_PHI]], [[BB7]] ], [ 0, [[BB]] ], [ [[DOTSI_UNFOLD_PHI1]], [[SEL_SI_UNFOLD_FALSE]] ], [ [[SEL_SI_UNFOLD_PHI]], [[BB7_JT0]] ]
+; CHECK-NEXT: br i1 [[NOT:%.*]], label [[BB7_JT0]], label [[BB2:%.*]]
+; CHECK: BB2:
+; CHECK-NEXT: store i16 0, ptr [[D:%.*]], align 2
+; CHECK-NEXT: br i1 [[CMP2:%.*]], label [[BB7]], label [[SPEC_SELECT_SI_UNFOLD_FALSE_JT0:%.*]]
+; CHECK: spec.select.si.unfold.false:
+; CHECK-NEXT: br label [[BB7]]
+; CHECK: spec.select.si.unfold.false.jt0:
+; CHECK-NEXT: [[DOTSI_UNFOLD_PHI_JT0:%.*]] = phi i32 [ 0, [[BB2]] ]
+; CHECK-NEXT: br label [[BB7_JT0]]
+; CHECK: BB7:
+; CHECK-NEXT: [[D_PROMOTED4:%.*]] = phi i16 [ 1, [[BB2]] ], [ 1, [[SPEC_SELECT_SI_UNFOLD_FALSE:%.*]] ]
+; CHECK-NEXT: [[_3:%.*]] = phi i32 [ [[SEL_SI_UNFOLD_PHI]], [[BB2]] ], [ poison, [[SPEC_SELECT_SI_UNFOLD_FALSE]] ]
+; CHECK-NEXT: switch i32 [[_3]], label [[BB1_BACKEDGE]] [
+; CHECK-NEXT: i32 0, label [[BB1]]
+; CHECK-NEXT: i32 1, label [[BB8:%.*]]
+; CHECK-NEXT: ]
+; CHECK: BB7.jt0:
+; CHECK-NEXT: [[D_PROMOTED4_JT0:%.*]] = phi i16 [ 0, [[BB1]] ], [ 1, [[SPEC_SELECT_SI_UNFOLD_FALSE_JT0]] ]
+; CHECK-NEXT: [[_3_JT0:%.*]] = phi i32 [ 0, [[BB1]] ], [ [[DOTSI_UNFOLD_PHI_JT0]], [[SPEC_SELECT_SI_UNFOLD_FALSE_JT0]] ]
+; CHECK-NEXT: br label [[BB1]]
+; CHECK: BB1.backedge:
+; CHECK-NEXT: br label [[BB1]]
+; CHECK: BB8:
+; CHECK-NEXT: ret void
+;
+bb:
+ %sel = select i1 %cmp1, i32 0, i32 1
+ br label %BB1
+
+BB1: ; preds = %BB1.backedge, %BB7, %bb
+ %i = phi i16 [ 0, %BB1.backedge ], [ 0, %bb ], [ 1, %BB7 ]
+ br i1 %not, label %BB7, label %BB2
+
+BB2: ; preds = %BB1
+ store i16 0, ptr %d, align 2
+ %spec.select = select i1 %cmp2, i32 %sel, i32 0
+ br label %BB7
+
+BB7: ; preds = %BB2, %BB1
+ %d.promoted4 = phi i16 [ 0, %BB1 ], [ 1, %BB2 ]
+ %_3 = phi i32 [ 0, %BB1 ], [ %spec.select, %BB2 ]
+ switch i32 %_3, label %BB1.backedge [
+ i32 0, label %BB1
+ i32 1, label %BB8
+ ]
+
+BB1.backedge: ; preds = %BB7
+ br label %BB1
+
+BB8: ; preds = %BB7
+ ret void
+}
+
+define void @pr106083_select_dead_uses(i1 %cmp1, i1 %not, ptr %p) {
+; CHECK-LABEL: @pr106083_select_dead_uses(
+; CHECK-NEXT: bb:
+; CHECK-NEXT: br i1 [[CMP1:%.*]], label [[DOTLOOPEXIT6:%.*]], label [[SPEC_SELECT_SI_UNFOLD_FALSE:%.*]]
+; CHECK: spec.select.si.unfold.false:
+; CHECK-NEXT: [[DOTSI_UNFOLD_PHI1:%.*]] = phi i32 [ 1, [[BB:%.*]] ]
+; CHECK-NEXT: br label [[DOTLOOPEXIT6]]
+; CHECK: .loopexit6:
+; CHECK-NEXT: [[SPEC_SELECT_SI_UNFOLD_PHI:%.*]] = phi i32 [ [[SPEC_SELECT_SI_UNFOLD_PHI]], [[SELECT_UNFOLD:%.*]] ], [ 0, [[BB]] ], [ [[DOTSI_UNFOLD_PHI1]], [[SPEC_SELECT_SI_UNFOLD_FALSE]] ]
+; CHECK-NEXT: br i1 [[NOT:%.*]], label [[SELECT_UNFOLD_JT0:%.*]], label [[BB1:%.*]]
+; CHECK: bb1:
+; CHECK-NEXT: [[I:%.*]] = load i32, ptr [[P:%.*]], align 4
+; CHECK-NEXT: [[NOT2:%.*]] = icmp eq i32 0, 0
+; CHECK-NEXT: br i1 [[NOT2]], label [[SELECT_UNFOLD]], label [[SPEC_SELECT7_SI_UNFOLD_FALSE_JT0:%.*]]
+; CHECK: spec.select7.si.unfold.false:
+; CHECK-NEXT: br label [[SELECT_UNFOLD]]
+; CHECK: spec.select7.si.unfold.false.jt0:
+; CHECK-NEXT: [[DOTSI_UNFOLD_PHI_JT0:%.*]] = phi i32 [ 0, [[BB1]] ]
+; CHECK-NEXT: br label [[SELECT_UNFOLD_JT0]]
+; CHECK: select.unfold:
+; CHECK-NEXT: [[_2:%.*]] = phi i32 [ [[SPEC_SELECT_SI_UNFOLD_PHI]], [[BB1]] ], [ poison, [[SPEC_SELECT7_SI_UNFOLD_FALSE:%.*]] ]
+; CHECK-NEXT: switch i32 [[_2]], label [[BB2:%.*]] [
+; CHECK-NEXT: i32 0, label [[DOTPREHEADER_PREHEADER:%.*]]
+; CHECK-NEXT: i32 1, label [[DOTLOOPEXIT6]]
+; CHECK-NEXT: ]
+; CHECK: select.unfold.jt0:
+; CHECK-NEXT: [[_2_JT0:%.*]] = phi i32 [ 0, [[DOTLOOPEXIT6]] ], [ [[DOTSI_UNFOLD_PHI_JT0]], [[SPEC_SELECT7_SI_UNFOLD_FALSE_JT0]] ]
+; CHECK-NEXT: br label [[DOTPREHEADER_PREHEADER]]
+; CHECK: .preheader.preheader:
+; CHECK-NEXT: ret void
+; CHECK: bb2:
+; CHECK-NEXT: unreachable
+;
+bb:
+ %spec.select = select i1 %cmp1, i32 0, i32 1
+ br label %.loopexit6
+
+.loopexit6: ; preds = %select.unfold, %bb
+ br i1 %not, label %select.unfold, label %bb1
+
+bb1: ; preds = %.loopexit6
+ %i = load i32, ptr %p, align 4
+ %not2 = icmp eq i32 0, 0
+ %spec.select7 = select i1 %not2, i32 %spec.select, i32 0
+ br label %select.unfold
+
+select.unfold: ; preds = %bb1, %.loopexit6
+ %_2 = phi i32 [ 0, %.loopexit6 ], [ %spec.select7, %bb1 ]
+ switch i32 %_2, label %bb2 [
+ i32 0, label %.preheader.preheader
+ i32 1, label %.loopexit6
+ ]
+
+.preheader.preheader: ; preds = %select.unfold
+ ret void
+
+bb2: ; preds = %select.unfold
+ unreachable
+}
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