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InstCombine: extend select-equiv to support vectors #111966

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Merged
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Oct 15, 2024
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InstCombine: extend select-equiv to support vectors #111966

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4 changes: 3 additions & 1 deletion llvm/lib/Analysis/ValueTracking.cpp
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Expand Up @@ -6950,7 +6950,9 @@ bool llvm::onlyUsedByLifetimeMarkersOrDroppableInsts(const Value *V) {
bool llvm::isNotCrossLaneOperation(const Instruction *I) {
if (auto *II = dyn_cast<IntrinsicInst>(I))
return isTriviallyVectorizable(II->getIntrinsicID());
return !isa<CallBase, BitCastInst, ShuffleVectorInst, ExtractElementInst>(I);
auto *Shuffle = dyn_cast<ShuffleVectorInst>(I);
return (!Shuffle || Shuffle->isSelect()) &&
!isa<CallBase, BitCastInst, ExtractElementInst>(I);
}

bool llvm::isSafeToSpeculativelyExecute(const Instruction *Inst,
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7 changes: 5 additions & 2 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Expand Up @@ -1288,6 +1288,10 @@ bool InstCombinerImpl::replaceInInstruction(Value *V, Value *Old, Value *New,
!isSafeToSpeculativelyExecuteWithVariableReplaced(I))
return false;

// Forbid potentially lane-crossing instructions.
if (Old->getType()->isVectorTy() && !isNotCrossLaneOperation(I))
return false;

bool Changed = false;
for (Use &U : I->operands()) {
if (U == Old) {
Expand Down Expand Up @@ -1366,9 +1370,8 @@ Instruction *InstCombinerImpl::foldSelectValueEquivalence(SelectInst &Sel,
// with different operands, which should not cause side-effects or trigger
// undefined behavior). Only do this if CmpRHS is a constant, as
// profitability is not clear for other cases.
// FIXME: Support vectors.
if (OldOp == CmpLHS && match(NewOp, m_ImmConstant()) &&
!match(OldOp, m_Constant()) && !Cmp.getType()->isVectorTy() &&
!match(OldOp, m_Constant()) &&
isGuaranteedNotToBeUndef(NewOp, SQ.AC, &Sel, &DT))
if (replaceInInstruction(TrueVal, OldOp, NewOp))
return &Sel;
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2 changes: 1 addition & 1 deletion llvm/test/Transforms/InstCombine/and-or-icmps.ll
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Expand Up @@ -983,7 +983,7 @@ define <2 x i1> @substitute_constant_or_ne_slt_swap_vec_poison(<2 x i8> %x, <2 x
define <2 x i1> @substitute_constant_or_ne_slt_swap_vec_logical(<2 x i8> %x, <2 x i8> %y) {
; CHECK-LABEL: @substitute_constant_or_ne_slt_swap_vec_logical(
; CHECK-NEXT: [[C1:%.*]] = icmp ne <2 x i8> [[X:%.*]], <i8 42, i8 poison>
; CHECK-NEXT: [[C2:%.*]] = icmp slt <2 x i8> [[Y:%.*]], [[X]]
; CHECK-NEXT: [[C2:%.*]] = icmp slt <2 x i8> [[Y:%.*]], <i8 42, i8 poison>
; CHECK-NEXT: [[R:%.*]] = select <2 x i1> [[C1]], <2 x i1> <i1 true, i1 true>, <2 x i1> [[C2]]
; CHECK-NEXT: ret <2 x i1> [[R]]
;
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10 changes: 5 additions & 5 deletions llvm/test/Transforms/InstCombine/select-binop-cmp.ll
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Expand Up @@ -552,12 +552,12 @@ define i32 @select_xor_icmp_bad_6(i32 %x, i32 %y, i32 %z) {
ret i32 %C
}

; Value equivalence substitution is all-or-nothing, so needs a scalar compare.
; Value equivalence substitution is valid.

define <2 x i8> @select_xor_icmp_vec_bad(<2 x i8> %x, <2 x i8> %y, <2 x i8> %z) {
; CHECK-LABEL: @select_xor_icmp_vec_bad(
define <2 x i8> @select_xor_icmp_vec_equivalence(<2 x i8> %x, <2 x i8> %y, <2 x i8> %z) {
; CHECK-LABEL: @select_xor_icmp_vec_equivalence(
; CHECK-NEXT: [[A:%.*]] = icmp eq <2 x i8> [[X:%.*]], <i8 5, i8 3>
; CHECK-NEXT: [[B:%.*]] = xor <2 x i8> [[X]], [[Z:%.*]]
; CHECK-NEXT: [[B:%.*]] = xor <2 x i8> [[Z:%.*]], <i8 5, i8 3>
; CHECK-NEXT: [[C:%.*]] = select <2 x i1> [[A]], <2 x i8> [[B]], <2 x i8> [[Y:%.*]]
; CHECK-NEXT: ret <2 x i8> [[C]]
;
Expand All @@ -567,7 +567,7 @@ define <2 x i8> @select_xor_icmp_vec_bad(<2 x i8> %x, <2 x i8> %y, <2 x i8> %z)
ret <2 x i8> %C
}

; Value equivalence substitution is all-or-nothing, so needs a scalar compare.
; Value equivalence substitution is invalid due to lane-crossing shufflevector.

define <2 x i32> @vec_select_no_equivalence(<2 x i32> %x) {
; CHECK-LABEL: @vec_select_no_equivalence(
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6 changes: 3 additions & 3 deletions llvm/test/Transforms/InstCombine/select-value-equivalence.ll
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Expand Up @@ -5,7 +5,7 @@ define <2 x i8> @select_icmp_insertelement_eq(<2 x i8> %x, <2 x i8> %y, i8 %i) {
; CHECK-LABEL: define <2 x i8> @select_icmp_insertelement_eq(
; CHECK-SAME: <2 x i8> [[X:%.*]], <2 x i8> [[Y:%.*]], i8 [[I:%.*]]) {
; CHECK-NEXT: [[CMP:%.*]] = icmp eq <2 x i8> [[Y]], <i8 2, i8 2>
; CHECK-NEXT: [[INSERT:%.*]] = insertelement <2 x i8> [[Y]], i8 0, i8 [[I]]
; CHECK-NEXT: [[INSERT:%.*]] = insertelement <2 x i8> <i8 2, i8 2>, i8 0, i8 [[I]]
; CHECK-NEXT: [[RETVAL:%.*]] = select <2 x i1> [[CMP]], <2 x i8> [[INSERT]], <2 x i8> [[X]]
; CHECK-NEXT: ret <2 x i8> [[RETVAL]]
;
Expand All @@ -19,7 +19,7 @@ define <2 x i8> @select_icmp_insertelement_ne(<2 x i8> %x, <2 x i8> %y, i8 %i) {
; CHECK-LABEL: define <2 x i8> @select_icmp_insertelement_ne(
; CHECK-SAME: <2 x i8> [[X:%.*]], <2 x i8> [[Y:%.*]], i8 [[I:%.*]]) {
; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp eq <2 x i8> [[Y]], <i8 2, i8 2>
; CHECK-NEXT: [[INSERT:%.*]] = insertelement <2 x i8> [[Y]], i8 0, i8 [[I]]
; CHECK-NEXT: [[INSERT:%.*]] = insertelement <2 x i8> <i8 2, i8 2>, i8 0, i8 [[I]]
; CHECK-NEXT: [[RETVAL:%.*]] = select <2 x i1> [[CMP_NOT]], <2 x i8> [[INSERT]], <2 x i8> [[X]]
; CHECK-NEXT: ret <2 x i8> [[RETVAL]]
;
Expand All @@ -46,7 +46,7 @@ define <4 x i8> @select_icmp_shufflevector_select(<4 x i8> %x, <4 x i8> %y, <4 x
; CHECK-LABEL: define <4 x i8> @select_icmp_shufflevector_select(
; CHECK-SAME: <4 x i8> [[X:%.*]], <4 x i8> [[Y:%.*]], <4 x i8> [[Z:%.*]]) {
; CHECK-NEXT: [[CMP:%.*]] = icmp eq <4 x i8> [[Y]], <i8 2, i8 2, i8 2, i8 2>
; CHECK-NEXT: [[SHUFFLE:%.*]] = shufflevector <4 x i8> [[Z]], <4 x i8> [[Y]], <4 x i32> <i32 0, i32 5, i32 2, i32 7>
; CHECK-NEXT: [[SHUFFLE:%.*]] = shufflevector <4 x i8> [[Z]], <4 x i8> <i8 poison, i8 2, i8 poison, i8 2>, <4 x i32> <i32 0, i32 5, i32 2, i32 7>
; CHECK-NEXT: [[RETVAL:%.*]] = select <4 x i1> [[CMP]], <4 x i8> [[SHUFFLE]], <4 x i8> [[X]]
; CHECK-NEXT: ret <4 x i8> [[RETVAL]]
;
Expand Down
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