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[InstCombine] Enable select freeze poison folding when storing value #129776

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Merged
merged 1 commit into from
Mar 20, 2025
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[InstCombine] Enable select freeze poison folding when storing value #129776

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44 changes: 33 additions & 11 deletions llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4812,19 +4812,23 @@ Instruction *InstCombinerImpl::visitFreeze(FreezeInst &I) {
//
// TODO: This could use getBinopAbsorber() / getBinopIdentity() to avoid
// duplicating logic for binops at least.
auto getUndefReplacement = [&I](Type *Ty) {
Constant *BestValue = nullptr;
Constant *NullValue = Constant::getNullValue(Ty);
auto getUndefReplacement = [&](Type *Ty) {
Value *BestValue = nullptr;
Value *NullValue = Constant::getNullValue(Ty);
for (const auto *U : I.users()) {
Constant *C = NullValue;
Value *V = NullValue;
if (match(U, m_Or(m_Value(), m_Value())))
C = ConstantInt::getAllOnesValue(Ty);
V = ConstantInt::getAllOnesValue(Ty);
else if (match(U, m_Select(m_Specific(&I), m_Constant(), m_Value())))
C = ConstantInt::getTrue(Ty);
V = ConstantInt::getTrue(Ty);
else if (match(U, m_c_Select(m_Specific(&I), m_Value(V)))) {
if (!isGuaranteedNotToBeUndefOrPoison(V, &AC, &I, &DT))
V = NullValue;
}

if (!BestValue)
BestValue = C;
else if (BestValue != C)
BestValue = V;
else if (BestValue != V)
BestValue = NullValue;
}
assert(BestValue && "Must have at least one use");
Expand All @@ -4840,10 +4844,28 @@ Instruction *InstCombinerImpl::visitFreeze(FreezeInst &I) {
return replaceInstUsesWith(I, getUndefReplacement(I.getType()));
}

auto getFreezeVectorReplacement = [](Constant *C) -> Constant * {
Type *Ty = C->getType();
auto *VTy = dyn_cast<FixedVectorType>(Ty);
if (!VTy)
return nullptr;
unsigned NumElts = VTy->getNumElements();
Constant *BestValue = Constant::getNullValue(VTy->getScalarType());
for (unsigned i = 0; i != NumElts; ++i) {
Constant *EltC = C->getAggregateElement(i);
if (EltC && !match(EltC, m_Undef())) {
BestValue = EltC;
break;
}
}
return Constant::replaceUndefsWith(C, BestValue);
};

Constant *C;
if (match(Op0, m_Constant(C)) && C->containsUndefOrPoisonElement()) {
Constant *ReplaceC = getUndefReplacement(I.getType()->getScalarType());
return replaceInstUsesWith(I, Constant::replaceUndefsWith(C, ReplaceC));
if (match(Op0, m_Constant(C)) && C->containsUndefOrPoisonElement() &&
!C->containsConstantExpression()) {
if (Constant *Repl = getFreezeVectorReplacement(C))
return replaceInstUsesWith(I, Repl);
}

// Replace uses of Op with freeze(Op).
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/Transforms/InstCombine/freeze-phi.ll
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Expand Up @@ -53,7 +53,7 @@ define <2 x i32> @vec_undef(i1 %cond) {
; CHECK: B:
; CHECK-NEXT: br label [[C]]
; CHECK: C:
; CHECK-NEXT: [[Y:%.*]] = phi <2 x i32> [ <i32 0, i32 1>, [[A]] ], [ <i32 2, i32 0>, [[B]] ]
; CHECK-NEXT: [[Y:%.*]] = phi <2 x i32> [ <i32 0, i32 1>, [[A]] ], [ splat (i32 2), [[B]] ]
; CHECK-NEXT: ret <2 x i32> [[Y]]
;
br i1 %cond, label %A, label %B
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/Transforms/InstCombine/freeze.ll
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Expand Up @@ -90,7 +90,7 @@ define void @or_select_multipleuses_logical(i32 %x, i1 %y) {

define <3 x i4> @partial_undef_vec() {
; CHECK-LABEL: @partial_undef_vec(
; CHECK-NEXT: ret <3 x i4> <i4 0, i4 1, i4 0>
; CHECK-NEXT: ret <3 x i4> splat (i4 1)
;
%f = freeze <3 x i4> <i4 poison, i4 1, i4 undef>
ret <3 x i4> %f
Expand Down
127 changes: 118 additions & 9 deletions llvm/test/Transforms/InstCombine/select.ll
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Expand Up @@ -2652,8 +2652,7 @@ define <2 x i8> @partial_cond_freeze_constant_true_val_vec(<2 x i8> %x) {

define <2 x i8> @partial_cond_freeze_constant_false_val_vec(<2 x i8> %x) {
; CHECK-LABEL: @partial_cond_freeze_constant_false_val_vec(
; CHECK-NEXT: [[S1:%.*]] = insertelement <2 x i8> [[X:%.*]], i8 2, i64 1
; CHECK-NEXT: ret <2 x i8> [[S1]]
; CHECK-NEXT: ret <2 x i8> [[X:%.*]]
;
%cond.fr = freeze <2 x i1> <i1 true, i1 undef>
%s = select <2 x i1> %cond.fr, <2 x i8> %x, <2 x i8> <i8 1, i8 2>
Expand All @@ -2662,7 +2661,7 @@ define <2 x i8> @partial_cond_freeze_constant_false_val_vec(<2 x i8> %x) {

define <2 x i8> @partial_cond_freeze_both_arms_constant_vec() {
; CHECK-LABEL: @partial_cond_freeze_both_arms_constant_vec(
; CHECK-NEXT: ret <2 x i8> <i8 42, i8 2>
; CHECK-NEXT: ret <2 x i8> <i8 42, i8 43>
;
%cond.fr = freeze <2 x i1> <i1 false, i1 undef>
%s = select <2 x i1> %cond.fr, <2 x i8> <i8 1, i8 2>, <2 x i8> <i8 42, i8 43>
Expand Down Expand Up @@ -4904,8 +4903,7 @@ define i32 @src_simplify_2x_at_once_and(i32 %x, i32 %y) {

define void @select_freeze_poison_parameter(ptr noundef %addr.src, ptr %addr.tgt, i1 %cond) {
; CHECK-LABEL: @select_freeze_poison_parameter(
; CHECK-NEXT: [[ADDR_SRC:%.*]] = select i1 [[COND:%.*]], ptr [[ADDR_SRC1:%.*]], ptr null
; CHECK-NEXT: store ptr [[ADDR_SRC]], ptr [[ADDR_TGT:%.*]], align 8
; CHECK-NEXT: store ptr [[ADDR_SRC:%.*]], ptr [[ADDR_TGT:%.*]], align 8
; CHECK-NEXT: ret void
;
%freeze = freeze ptr poison
Expand All @@ -4914,12 +4912,47 @@ define void @select_freeze_poison_parameter(ptr noundef %addr.src, ptr %addr.tgt
ret void
}

define i8 @select_freeze_poison_different_parameters(i8 noundef %x, i8 noundef %y, i1 %cond1, i1 %cond2) {
; CHECK-LABEL: @select_freeze_poison_different_parameters(
; CHECK-NEXT: [[SEL1:%.*]] = select i1 [[COND1:%.*]], i8 [[X:%.*]], i8 0
; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[COND2:%.*]], i8 [[Y:%.*]], i8 0
; CHECK-NEXT: [[CONJ:%.*]] = and i8 [[SEL1]], [[SEL2]]
; CHECK-NEXT: ret i8 [[CONJ]]
;
%freeze = freeze i8 poison
%sel1 = select i1 %cond1, i8 %x, i8 %freeze
%sel2 = select i1 %cond2, i8 %y, i8 %freeze
%conj = and i8 %sel1, %sel2
ret i8 %conj
}

define i8 @select_or_freeze_poison_parameter(i8 noundef %x, i1 %cond1) {
; CHECK-LABEL: @select_or_freeze_poison_parameter(
; CHECK-NEXT: ret i8 -1
;
%freeze = freeze i8 poison
%sel1 = select i1 %cond1, i8 -1, i8 %freeze
%or1 = or i8 %x, %freeze
%conj = and i8 %sel1, %or1
ret i8 %conj
}

define i8 @selects_freeze_poison_parameter(i8 noundef %x, i1 %cond1, i1 %cond2) {
; CHECK-LABEL: @selects_freeze_poison_parameter(
; CHECK-NEXT: ret i8 [[X:%.*]]
;
%freeze = freeze i8 poison
%sel1 = select i1 %cond1, i8 %x, i8 %freeze
%sel2 = select i1 %cond2, i8 %x, i8 %freeze
%conj = and i8 %sel1, %sel2
ret i8 %conj
}

@glb = global ptr null

define void @select_freeze_poison_global(ptr %addr.tgt, i1 %cond) {
; CHECK-LABEL: @select_freeze_poison_global(
; CHECK-NEXT: [[SELECT_ADDR:%.*]] = select i1 [[COND:%.*]], ptr @glb, ptr null
; CHECK-NEXT: store ptr [[SELECT_ADDR]], ptr [[ADDR_TGT:%.*]], align 8
; CHECK-NEXT: store ptr @glb, ptr [[ADDR_TGT:%.*]], align 8
; CHECK-NEXT: ret void
;
%freeze = freeze ptr poison
Expand All @@ -4930,12 +4963,88 @@ define void @select_freeze_poison_global(ptr %addr.tgt, i1 %cond) {

define void @select_freeze_poison_constant(ptr %addr.tgt, i1 %cond) {
; CHECK-LABEL: @select_freeze_poison_constant(
; CHECK-NEXT: [[SELECT_ADDR:%.*]] = select i1 [[COND:%.*]], i32 72, i32 0
; CHECK-NEXT: store i32 [[SELECT_ADDR]], ptr [[ADDR_TGT:%.*]], align 4
; CHECK-NEXT: store i32 72, ptr [[ADDR_TGT:%.*]], align 4
; CHECK-NEXT: ret void
;
%freeze = freeze i32 poison
%select.addr = select i1 %cond, i32 72, i32 %freeze
store i32 %select.addr, ptr %addr.tgt
ret void
}

define <2 x i8> @select_freeze_poison_mask_vector(i1 %cond, <2 x i8> noundef %y) {
; CHECK-LABEL: @select_freeze_poison_mask_vector(
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[COND:%.*]], <2 x i8> [[Y:%.*]], <2 x i8> zeroinitializer
; CHECK-NEXT: ret <2 x i8> [[SEL]]
;
%freeze = freeze <2 x i8> <i8 0, i8 poison>
%sel = select i1 %cond, <2 x i8> %y, <2 x i8> %freeze
ret <2 x i8> %sel
}

define <2 x i8> @selects_freeze_poison_mask_vector(<2 x i8> noundef %x, i1 %cond1, i1 %cond2) {
; CHECK-LABEL: @selects_freeze_poison_mask_vector(
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[COND1:%.*]], i1 [[COND2:%.*]], i1 false
; CHECK-NEXT: [[X:%.*]] = select i1 [[TMP1]], <2 x i8> [[X1:%.*]], <2 x i8> zeroinitializer
; CHECK-NEXT: ret <2 x i8> [[X]]
;
%freeze = freeze <2 x i8> <i8 0, i8 poison>
%sel1 = select i1 %cond1, <2 x i8> %x, <2 x i8> %freeze
%sel2 = select i1 %cond2, <2 x i8> %x, <2 x i8> %freeze
%conj = and <2 x i8> %sel1, %sel2
ret <2 x i8> %conj
}

define <2 x i8> @select_freeze_poison_splat_vector(i1 %cond, <2 x i8> noundef %y) {
; CHECK-LABEL: @select_freeze_poison_splat_vector(
; CHECK-NEXT: ret <2 x i8> [[Y:%.*]]
;
%freeze = freeze <2 x i8> <i8 poison, i8 poison>
%sel = select i1 %cond, <2 x i8> %y, <2 x i8> %freeze
ret <2 x i8> %sel
}

define <2 x i8> @selects_freeze_poison_splat_vector(<2 x i8> noundef %x, i1 %cond1, i1 %cond2) {
; CHECK-LABEL: @selects_freeze_poison_splat_vector(
; CHECK-NEXT: ret <2 x i8> [[X:%.*]]
;
%freeze = freeze <2 x i8> <i8 poison, i8 poison>
%sel1 = select i1 %cond1, <2 x i8> %x, <2 x i8> %freeze
%sel2 = select i1 %cond2, <2 x i8> %x, <2 x i8> %freeze
%conj = and <2 x i8> %sel1, %sel2
ret <2 x i8> %conj
}

define <2 x i8> @select_freeze_constant_vector(i1 %cond, <2 x i8> noundef %y) {
; CHECK-LABEL: @select_freeze_constant_vector(
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[COND:%.*]], <2 x i8> [[Y:%.*]], <2 x i8> zeroinitializer
; CHECK-NEXT: ret <2 x i8> [[SEL]]
;
%freeze = freeze <2 x i8> <i8 0, i8 0>
%sel = select i1 %cond, <2 x i8> %y, <2 x i8> %freeze
ret <2 x i8> %sel
}

define <2 x i8> @select_freeze_constant_expression_vector_add(i1 %cond, <2 x i8> noundef %y) {
; CHECK-LABEL: @select_freeze_constant_expression_vector_add(
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[COND:%.*]], <2 x i8> [[Y:%.*]], <2 x i8> splat (i8 3)
; CHECK-NEXT: ret <2 x i8> [[SEL]]
;
%freeze = freeze <2 x i8> <i8 poison, i8 add (i8 1, i8 2)>
%sel = select i1 %cond, <2 x i8> %y, <2 x i8> %freeze
ret <2 x i8> %sel
}

%struct.1 = type {i32, i32}
@glb.struct.1 = global %struct.1 {i32 1, i32 2}

define <2 x ptr> @select_freeze_constant_expression_vector_gep(i1 %cond, <2 x ptr> noundef %y) {
; CHECK-LABEL: @select_freeze_constant_expression_vector_gep(
; CHECK-NEXT: [[FREEZE:%.*]] = freeze <2 x ptr> <ptr poison, ptr getelementptr inbounds nuw (i8, ptr @glb.struct.1, i64 800)>
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[COND:%.*]], <2 x ptr> [[Y:%.*]], <2 x ptr> [[FREEZE]]
; CHECK-NEXT: ret <2 x ptr> [[SEL]]
;
%freeze = freeze <2 x ptr> <ptr poison, ptr getelementptr inbounds (%struct.1, ptr @glb.struct.1, i64 100)>
%sel = select i1 %cond, <2 x ptr> %y, <2 x ptr> %freeze
ret <2 x ptr> %sel
}
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