[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
This commit is contained in:
Usman Nadeem 2024-09-24 08:54:36 -07:00 committed by GitHub
parent d075debc50
commit d4a38c8ff5
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
2 changed files with 152 additions and 17 deletions

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@ -194,7 +194,6 @@ void unfold(DomTreeUpdater *DTU, LoopInfo *LI, SelectInstToUnfold SIToUnfold,
SelectInst *SI = SIToUnfold.getInst(); SelectInst *SI = SIToUnfold.getInst();
PHINode *SIUse = SIToUnfold.getUse(); PHINode *SIUse = SIToUnfold.getUse();
BasicBlock *StartBlock = SI->getParent(); BasicBlock *StartBlock = SI->getParent();
BasicBlock *EndBlock = SIUse->getParent();
BranchInst *StartBlockTerm = BranchInst *StartBlockTerm =
dyn_cast<BranchInst>(StartBlock->getTerminator()); dyn_cast<BranchInst>(StartBlock->getTerminator());
@ -202,6 +201,7 @@ void unfold(DomTreeUpdater *DTU, LoopInfo *LI, SelectInstToUnfold SIToUnfold,
assert(SI->hasOneUse()); assert(SI->hasOneUse());
if (StartBlockTerm->isUnconditional()) { if (StartBlockTerm->isUnconditional()) {
BasicBlock *EndBlock = StartBlock->getUniqueSuccessor();
// Arbitrarily choose the 'false' side for a new input value to the PHI. // Arbitrarily choose the 'false' side for a new input value to the PHI.
BasicBlock *NewBlock = BasicBlock::Create( BasicBlock *NewBlock = BasicBlock::Create(
SI->getContext(), Twine(SI->getName(), ".si.unfold.false"), SI->getContext(), Twine(SI->getName(), ".si.unfold.false"),
@ -223,32 +223,44 @@ void unfold(DomTreeUpdater *DTU, LoopInfo *LI, SelectInstToUnfold SIToUnfold,
NewBlock->getFirstInsertionPt()); NewBlock->getFirstInsertionPt());
NewPhi->addIncoming(SIOp2, StartBlock); NewPhi->addIncoming(SIOp2, StartBlock);
// Update any other PHI nodes in EndBlock.
for (PHINode &Phi : EndBlock->phis()) {
if (SIUse == &Phi)
continue;
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;
}
if (auto *OpSi = dyn_cast<SelectInst>(SIOp1)) if (auto *OpSi = dyn_cast<SelectInst>(SIOp1))
NewSIsToUnfold->push_back(SelectInstToUnfold(OpSi, SIUse)); NewSIsToUnfold->push_back(SelectInstToUnfold(OpSi, SIUse));
if (auto *OpSi = dyn_cast<SelectInst>(SIOp2)) if (auto *OpSi = dyn_cast<SelectInst>(SIOp2))
NewSIsToUnfold->push_back(SelectInstToUnfold(OpSi, NewPhi)); 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);
}
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);
}
StartBlockTerm->eraseFromParent();
// Insert the real conditional branch based on the original condition. // Insert the real conditional branch based on the original condition.
StartBlockTerm->eraseFromParent();
BranchInst::Create(EndBlock, NewBlock, SI->getCondition(), StartBlock); BranchInst::Create(EndBlock, NewBlock, SI->getCondition(), StartBlock);
DTU->applyUpdates({{DominatorTree::Insert, StartBlock, EndBlock}, DTU->applyUpdates({{DominatorTree::Insert, StartBlock, EndBlock},
{DominatorTree::Insert, StartBlock, NewBlock}}); {DominatorTree::Insert, StartBlock, NewBlock}});
} else { } else {
BasicBlock *EndBlock = SIUse->getParent();
BasicBlock *NewBlockT = BasicBlock::Create( BasicBlock *NewBlockT = BasicBlock::Create(
SI->getContext(), Twine(SI->getName(), ".si.unfold.true"), SI->getContext(), Twine(SI->getName(), ".si.unfold.true"),
EndBlock->getParent(), EndBlock); EndBlock->getParent(), EndBlock);

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@ -300,3 +300,126 @@ define void @self-reference() {
end: end:
ret void 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
}