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Fold Select with a Const Operand to BinOp
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@veera-sivarajan
veera-sivarajan committed Nov 19, 2024
1 parent 74f2e24 commit ef33107
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Showing 4 changed files with 74 additions and 48 deletions.
41 changes: 41 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1898,6 +1898,44 @@ static Instruction *foldSelectICmpEq(SelectInst &SI, ICmpInst *ICI,
return nullptr;
}

// Turn (select (Cmp X C1) (BOp X C2) C3)
// -> (select (Cmp X C1) (BOp X C2) (BOp C1 C2))
// -> (BOp (select (Cmp X C1) X C1) C2)
// iff C3 == BOp C1 C2
// This allows for better canonicalization.
static Instruction *canonicalizeConstToBOp(SelectInst &SI, Value *TrueVal,
Value *FalseVal,
InstCombinerImpl &IC) {
Value *CondVal = SI.getCondition();

BinaryOperator *BOp;
Constant *C1, *C2, *C3;
Value *X;
ICmpInst::Predicate Predicate;

if (!match(CondVal, m_c_ICmp(Predicate, m_Value(X), m_Constant(C1))))
return nullptr;

if (!((match(TrueVal, m_BinOp(BOp)) && match(FalseVal, m_Constant(C3))) ||
(match(FalseVal, m_BinOp(BOp)) && match(TrueVal, m_Constant(C3)))))
return nullptr;

if (!match(BOp, m_OneUse(m_c_BinOp(m_Specific(X), m_Constant(C2)))))
return nullptr;

if (!(ICmpInst::isRelational(Predicate) &&
C3 == ConstantFoldBinaryOpOperands(BOp->getOpcode(), C1, C2,
SI.getDataLayout())))
return nullptr;

Instruction *NewBO =
BinaryOperator::CreateWithCopiedFlags(BOp->getOpcode(), C1, C2, BOp);
IC.InsertNewInstBefore(NewBO, SI.getIterator());
IC.replaceOperand(SI, isa<Constant>(TrueVal) ? 1 : 2, NewBO);
return IC.foldSelectOpOp(SI, cast<Instruction>(SI.getTrueValue()),
cast<Instruction>(SI.getFalseValue()));
}

/// Visit a SelectInst that has an ICmpInst as its first operand.
Instruction *InstCombinerImpl::foldSelectInstWithICmp(SelectInst &SI,
ICmpInst *ICI) {
Expand Down Expand Up @@ -1990,6 +2028,9 @@ Instruction *InstCombinerImpl::foldSelectInstWithICmp(SelectInst &SI,
if (Value *V = foldAbsDiff(ICI, TrueVal, FalseVal, Builder))
return replaceInstUsesWith(SI, V);

if (Instruction *I = canonicalizeConstToBOp(SI, TrueVal, FalseVal, *this))
return I;

return Changed ? &SI : nullptr;
}

Expand Down
67 changes: 27 additions & 40 deletions llvm/test/Transforms/InstCombine/canonicalize-const-to-bop.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,8 @@
define i8 @add_and_sgt(i8 %x) {
; CHECK-LABEL: define i8 @add_and_sgt(
; CHECK-SAME: i8 [[X:%.*]]) {
; CHECK-NEXT: [[ADD:%.*]] = add nsw i8 [[X]], 16
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X]], 8
; CHECK-NEXT: [[S:%.*]] = select i1 [[CMP]], i8 [[ADD]], i8 24
; CHECK-NEXT: [[S_V:%.*]] = call i8 @llvm.smax.i8(i8 [[X]], i8 8)
; CHECK-NEXT: [[S:%.*]] = add nuw nsw i8 [[S_V]], 16
; CHECK-NEXT: ret i8 [[S]]
;
%add = add nsw i8 %x, 16
Expand All @@ -18,9 +17,8 @@ define i8 @add_and_sgt(i8 %x) {
define i8 @add_sgt_nuw(i8 %x) {
; CHECK-LABEL: define i8 @add_sgt_nuw(
; CHECK-SAME: i8 [[X:%.*]]) {
; CHECK-NEXT: [[ADD:%.*]] = add nuw i8 [[X]], 16
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X]], 8
; CHECK-NEXT: [[S:%.*]] = select i1 [[CMP]], i8 [[ADD]], i8 24
; CHECK-NEXT: [[S_V:%.*]] = call i8 @llvm.smax.i8(i8 [[X]], i8 8)
; CHECK-NEXT: [[S:%.*]] = add nuw i8 [[S_V]], 16
; CHECK-NEXT: ret i8 [[S]]
;
%add = add nuw i8 %x, 16
Expand All @@ -32,9 +30,8 @@ define i8 @add_sgt_nuw(i8 %x) {
define i8 @sub_and_ugt(i8 %x) {
; CHECK-LABEL: define i8 @sub_and_ugt(
; CHECK-SAME: i8 [[X:%.*]]) {
; CHECK-NEXT: [[SUB:%.*]] = add nsw i8 [[X]], -50
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[X]], 100
; CHECK-NEXT: [[S:%.*]] = select i1 [[CMP]], i8 50, i8 [[SUB]]
; CHECK-NEXT: [[S_V:%.*]] = call i8 @llvm.umin.i8(i8 [[X]], i8 100)
; CHECK-NEXT: [[S:%.*]] = add nsw i8 [[S_V]], -50
; CHECK-NEXT: ret i8 [[S]]
;
%sub = sub nsw i8 %x, 50
Expand All @@ -46,9 +43,8 @@ define i8 @sub_and_ugt(i8 %x) {
define i8 @sub_ugt_nuw_nsw(i8 %x) {
; CHECK-LABEL: define i8 @sub_ugt_nuw_nsw(
; CHECK-SAME: i8 [[X:%.*]]) {
; CHECK-NEXT: [[SUB:%.*]] = add nsw i8 [[X]], -50
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[X]], 100
; CHECK-NEXT: [[S:%.*]] = select i1 [[CMP]], i8 50, i8 [[SUB]]
; CHECK-NEXT: [[S_V:%.*]] = call i8 @llvm.umin.i8(i8 [[X]], i8 100)
; CHECK-NEXT: [[S:%.*]] = add nsw i8 [[S_V]], -50
; CHECK-NEXT: ret i8 [[S]]
;
%sub = sub nuw nsw i8 %x, 50
Expand All @@ -60,9 +56,8 @@ define i8 @sub_ugt_nuw_nsw(i8 %x) {
define i8 @mul_and_ult(i8 %x) {
; CHECK-LABEL: define i8 @mul_and_ult(
; CHECK-SAME: i8 [[X:%.*]]) {
; CHECK-NEXT: [[ADD:%.*]] = mul nsw i8 [[X]], 10
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[X]], 10
; CHECK-NEXT: [[S:%.*]] = select i1 [[CMP]], i8 100, i8 [[ADD]]
; CHECK-NEXT: [[S_V:%.*]] = call i8 @llvm.umin.i8(i8 [[X]], i8 10)
; CHECK-NEXT: [[S:%.*]] = mul nuw nsw i8 [[S_V]], 10
; CHECK-NEXT: ret i8 [[S]]
;
%add = mul nsw i8 %x, 10
Expand All @@ -74,9 +69,8 @@ define i8 @mul_and_ult(i8 %x) {
define i8 @mul_ult_noflags(i8 %x) {
; CHECK-LABEL: define i8 @mul_ult_noflags(
; CHECK-SAME: i8 [[X:%.*]]) {
; CHECK-NEXT: [[ADD:%.*]] = mul i8 [[X]], 10
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[X]], 10
; CHECK-NEXT: [[S:%.*]] = select i1 [[CMP]], i8 100, i8 [[ADD]]
; CHECK-NEXT: [[S_V:%.*]] = call i8 @llvm.umin.i8(i8 [[X]], i8 10)
; CHECK-NEXT: [[S:%.*]] = mul nuw i8 [[S_V]], 10
; CHECK-NEXT: ret i8 [[S]]
;
%add = mul i8 %x, 10
Expand All @@ -88,9 +82,8 @@ define i8 @mul_ult_noflags(i8 %x) {
define i8 @udiv_and_slt(i8 %x) {
; CHECK-LABEL: define i8 @udiv_and_slt(
; CHECK-SAME: i8 [[X:%.*]]) {
; CHECK-NEXT: [[SUB:%.*]] = udiv i8 [[X]], 10
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X]], 100
; CHECK-NEXT: [[S:%.*]] = select i1 [[CMP]], i8 10, i8 [[SUB]]
; CHECK-NEXT: [[S_V:%.*]] = call i8 @llvm.smax.i8(i8 [[X]], i8 100)
; CHECK-NEXT: [[S:%.*]] = udiv i8 [[S_V]], 10
; CHECK-NEXT: ret i8 [[S]]
;
%sub = udiv i8 %x, 10
Expand All @@ -102,9 +95,8 @@ define i8 @udiv_and_slt(i8 %x) {
define i8 @udiv_slt_exact(i8 %x) {
; CHECK-LABEL: define i8 @udiv_slt_exact(
; CHECK-SAME: i8 [[X:%.*]]) {
; CHECK-NEXT: [[SUB:%.*]] = udiv exact i8 [[X]], 10
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X]], 100
; CHECK-NEXT: [[S:%.*]] = select i1 [[CMP]], i8 10, i8 [[SUB]]
; CHECK-NEXT: [[S_V:%.*]] = call i8 @llvm.smax.i8(i8 [[X]], i8 100)
; CHECK-NEXT: [[S:%.*]] = udiv exact i8 [[S_V]], 10
; CHECK-NEXT: ret i8 [[S]]
;
%sub = udiv exact i8 %x, 10
Expand All @@ -116,9 +108,8 @@ define i8 @udiv_slt_exact(i8 %x) {
define i8 @canonicalize_icmp_operands(i8 %x) {
; CHECK-LABEL: define i8 @canonicalize_icmp_operands(
; CHECK-SAME: i8 [[X:%.*]]) {
; CHECK-NEXT: [[ADD:%.*]] = add nsw i8 [[X]], 8
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X]], 119
; CHECK-NEXT: [[S:%.*]] = select i1 [[CMP]], i8 127, i8 [[ADD]]
; CHECK-NEXT: [[S_V:%.*]] = call i8 @llvm.smin.i8(i8 [[X]], i8 119)
; CHECK-NEXT: [[S:%.*]] = add nsw i8 [[S_V]], 8
; CHECK-NEXT: ret i8 [[S]]
;
%add = add nsw i8 %x, 8
Expand All @@ -133,10 +124,10 @@ declare void @use_byte(i8)
define i8 @multi_use_cond_and_sel(i8 %x) {
; CHECK-LABEL: define i8 @multi_use_cond_and_sel(
; CHECK-SAME: i8 [[X:%.*]]) {
; CHECK-NEXT: [[ADD:%.*]] = add nsw i8 [[X]], 16
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X]], 8
; CHECK-NEXT: call void @use(i1 [[CMP]])
; CHECK-NEXT: [[S:%.*]] = select i1 [[CMP]], i8 [[ADD]], i8 24
; CHECK-NEXT: [[S_V:%.*]] = call i8 @llvm.smax.i8(i8 [[X]], i8 8)
; CHECK-NEXT: [[S:%.*]] = add nuw nsw i8 [[S_V]], 16
; CHECK-NEXT: call void @use_byte(i8 [[S]])
; CHECK-NEXT: ret i8 [[S]]
;
Expand All @@ -155,11 +146,9 @@ define void @rust_noop_loop() {
; CHECK: [[BB2_I]]:
; CHECK-NEXT: [[ITER_SROA_0_07:%.*]] = phi i32 [ 0, %[[START]] ], [ [[SPEC_SELECT5:%.*]], %[[BB2_I]] ]
; CHECK-NEXT: [[_0_I3_I:%.*]] = icmp sgt i32 [[ITER_SROA_0_07]], 99
; CHECK-NEXT: [[TMP0:%.*]] = add nsw i32 [[ITER_SROA_0_07]], 1
; CHECK-NEXT: [[SPEC_SELECT5]] = select i1 [[_0_I3_I]], i32 100, i32 [[TMP0]]
; CHECK-NEXT: [[_0_I_NOT_I:%.*]] = icmp sgt i32 [[SPEC_SELECT5]], 100
; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[_0_I3_I]], i1 true, i1 [[_0_I_NOT_I]]
; CHECK-NEXT: br i1 [[OR_COND]], label %[[BASICBLOCK4:.*]], label %[[BB2_I]]
; CHECK-NEXT: [[SPEC_SELECT5_V:%.*]] = call i32 @llvm.smin.i32(i32 [[ITER_SROA_0_07]], i32 99)
; CHECK-NEXT: [[SPEC_SELECT5]] = add nsw i32 [[SPEC_SELECT5_V]], 1
; CHECK-NEXT: br i1 [[_0_I3_I]], label %[[BASICBLOCK4:.*]], label %[[BB2_I]]
; CHECK: [[BASICBLOCK4]]:
; CHECK-NEXT: ret void
;
Expand All @@ -182,9 +171,8 @@ basicblock4:
define <2 x i8> @add_non_splat_vector(<2 x i8> %x) {
; CHECK-LABEL: define <2 x i8> @add_non_splat_vector(
; CHECK-SAME: <2 x i8> [[X:%.*]]) {
; CHECK-NEXT: [[ADD:%.*]] = add <2 x i8> [[X]], <i8 1, i8 0>
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i8> [[X]], <i8 0, i8 1>
; CHECK-NEXT: [[S:%.*]] = select <2 x i1> [[CMP]], <2 x i8> [[ADD]], <2 x i8> <i8 1, i8 1>
; CHECK-NEXT: [[S_V:%.*]] = call <2 x i8> @llvm.smax.v2i8(<2 x i8> [[X]], <2 x i8> <i8 0, i8 1>)
; CHECK-NEXT: [[S:%.*]] = add nuw <2 x i8> [[S_V]], <i8 1, i8 0>
; CHECK-NEXT: ret <2 x i8> [[S]]
;
%add = add <2 x i8> %x, <i8 1, i8 0>
Expand All @@ -196,9 +184,8 @@ define <2 x i8> @add_non_splat_vector(<2 x i8> %x) {
define <2 x i8> @or_splat_vector(<2 x i8> %x) {
; CHECK-LABEL: define <2 x i8> @or_splat_vector(
; CHECK-SAME: <2 x i8> [[X:%.*]]) {
; CHECK-NEXT: [[ADD:%.*]] = or <2 x i8> [[X]], <i8 1, i8 1>
; CHECK-NEXT: [[CMP_INV:%.*]] = icmp slt <2 x i8> [[X]], <i8 1, i8 1>
; CHECK-NEXT: [[S:%.*]] = select <2 x i1> [[CMP_INV]], <2 x i8> <i8 1, i8 1>, <2 x i8> [[ADD]]
; CHECK-NEXT: [[S_V:%.*]] = call <2 x i8> @llvm.smax.v2i8(<2 x i8> [[X]], <2 x i8> <i8 1, i8 1>)
; CHECK-NEXT: [[S:%.*]] = or <2 x i8> [[S_V]], <i8 1, i8 1>
; CHECK-NEXT: ret <2 x i8> [[S]]
;
%add = or <2 x i8> %x, <i8 1, i8 1>
Expand Down
7 changes: 3 additions & 4 deletions llvm/test/Transforms/InstCombine/saturating-add-sub.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -1793,10 +1793,9 @@ define i32 @not_uadd_sat(i32 %x, i32 %y) {

define i32 @not_uadd_sat2(i32 %x, i32 %y) {
; CHECK-LABEL: @not_uadd_sat2(
; CHECK-NEXT: [[A:%.*]] = add i32 [[X:%.*]], -2
; CHECK-NEXT: [[C:%.*]] = icmp ugt i32 [[X]], 1
; CHECK-NEXT: [[R:%.*]] = select i1 [[C]], i32 [[A]], i32 -1
; CHECK-NEXT: ret i32 [[R]]
; CHECK-NEXT: [[X:%.*]] = call i32 @llvm.umax.i32(i32 [[X1:%.*]], i32 1)
; CHECK-NEXT: [[A:%.*]] = add i32 [[X]], -2
; CHECK-NEXT: ret i32 [[A]]
;
%a = add i32 %x, -2
%c = icmp ugt i32 %x, 1
Expand Down
7 changes: 3 additions & 4 deletions llvm/test/Transforms/InstCombine/select.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -2989,10 +2989,9 @@ define i8 @select_replacement_loop3(i32 noundef %x) {

define i16 @select_replacement_loop4(i16 noundef %p_12) {
; CHECK-LABEL: @select_replacement_loop4(
; CHECK-NEXT: [[AND1:%.*]] = and i16 [[P_12:%.*]], 1
; CHECK-NEXT: [[CMP21:%.*]] = icmp ult i16 [[P_12]], 2
; CHECK-NEXT: [[AND3:%.*]] = select i1 [[CMP21]], i16 [[AND1]], i16 0
; CHECK-NEXT: ret i16 [[AND3]]
; CHECK-NEXT: [[P_12:%.*]] = call i16 @llvm.umin.i16(i16 [[P_13:%.*]], i16 2)
; CHECK-NEXT: [[AND1:%.*]] = and i16 [[P_12]], 1
; CHECK-NEXT: ret i16 [[AND1]]
;
%cmp1 = icmp ult i16 %p_12, 2
%and1 = and i16 %p_12, 1
Expand Down

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