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[InstSimplify] Fix simplifyAndOrWithICmpEq with undef refinement #98898

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Merged
merged 1 commit into from
Jul 16, 2024
Merged

[InstSimplify] Fix simplifyAndOrWithICmpEq with undef refinement #98898

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30 changes: 23 additions & 7 deletions llvm/lib/Analysis/InstructionSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1975,13 +1975,16 @@ static Value *simplifyAndOrWithICmpEq(unsigned Opcode, Value *Op0, Value *Op1,
return nullptr;
};

if (Value *Res =
simplifyWithOpReplaced(Op1, A, B, Q, /* AllowRefinement */ true,
/* DropFlags */ nullptr, MaxRecurse))
// In the final case (Res == Absorber with inverted predicate), it is safe to
// refine poison during simplification, but not undef. For simplicity always
// disable undef-based folds here.
if (Value *Res = simplifyWithOpReplaced(Op1, A, B, Q.getWithoutUndef(),
/* AllowRefinement */ true,
/* DropFlags */ nullptr, MaxRecurse))
return Simplify(Res);
if (Value *Res =
simplifyWithOpReplaced(Op1, B, A, Q, /* AllowRefinement */ true,
/* DropFlags */ nullptr, MaxRecurse))
if (Value *Res = simplifyWithOpReplaced(Op1, B, A, Q.getWithoutUndef(),
/* AllowRefinement */ true,
/* DropFlags */ nullptr, MaxRecurse))
return Simplify(Res);

return nullptr;
Expand Down Expand Up @@ -4300,6 +4303,9 @@ static Value *simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
bool AllowRefinement,
SmallVectorImpl<Instruction *> *DropFlags,
unsigned MaxRecurse) {
assert((AllowRefinement || !Q.CanUseUndef) &&
"If AllowRefinement=false then CanUseUndef=false");

// Trivial replacement.
if (V == Op)
return RepOp;
Expand Down Expand Up @@ -4347,6 +4353,11 @@ static Value *simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
} else {
NewOps.push_back(InstOp);
}

// Bail out if any operand is undef and SimplifyQuery disables undef
// simplification. Constant folding currently doesn't respect this option.
if (isa<UndefValue>(NewOps.back()) && !Q.CanUseUndef)
return nullptr;
}

if (!AnyReplaced)
Expand Down Expand Up @@ -4467,6 +4478,11 @@ Value *llvm::simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
const SimplifyQuery &Q,
bool AllowRefinement,
SmallVectorImpl<Instruction *> *DropFlags) {
// If refinement is disabled, also disable undef simplifications (which are
// always refinements) in SimplifyQuery.
if (!AllowRefinement)
return ::simplifyWithOpReplaced(V, Op, RepOp, Q.getWithoutUndef(),
AllowRefinement, DropFlags, RecursionLimit);
return ::simplifyWithOpReplaced(V, Op, RepOp, Q, AllowRefinement, DropFlags,
RecursionLimit);
}
Expand Down Expand Up @@ -4606,7 +4622,7 @@ static Value *simplifySelectWithICmpEq(Value *CmpLHS, Value *CmpRHS,
Value *TrueVal, Value *FalseVal,
const SimplifyQuery &Q,
unsigned MaxRecurse) {
if (simplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, Q,
if (simplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, Q.getWithoutUndef(),
/* AllowRefinement */ false,
/* DropFlags */ nullptr, MaxRecurse) == TrueVal)
return FalseVal;
Expand Down
4 changes: 2 additions & 2 deletions llvm/test/Transforms/InstSimplify/and-or-implied-cond.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -331,13 +331,13 @@ define i1 @and_is_constant(ptr %arg, ptr %arg2) {
ret i1 %and
}

; FIXME: This is a miscompile.
define i1 @pr98753(i32 noundef %x, i32 %y) {
; CHECK-LABEL: @pr98753(
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i32 [[X:%.*]], 0
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i32 [[Y:%.*]], i32 undef
; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 [[SEL]], 0
; CHECK-NEXT: ret i1 [[CMP2]]
; CHECK-NEXT: [[AND:%.*]] = and i1 [[CMP1]], [[CMP2]]
; CHECK-NEXT: ret i1 [[AND]]
;
%cmp1 = icmp ne i32 %x, 0
%sel = select i1 %cmp1, i32 %y, i32 undef
Expand Down
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