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[InstCombine] handle trunc to i1 in foldSelectICmpAndBinOp #127390

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Merged
merged 1 commit into from
Feb 19, 2025
Merged

[InstCombine] handle trunc to i1 in foldSelectICmpAndBinOp #127390

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62 changes: 35 additions & 27 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -742,39 +742,47 @@ static Value *foldSelectICmpLshrAshr(const ICmpInst *IC, Value *TrueVal,
/// 1. The icmp predicate is inverted
/// 2. The select operands are reversed
/// 3. The magnitude of C2 and C1 are flipped
static Value *foldSelectICmpAndBinOp(const ICmpInst *IC, Value *TrueVal,
Value *FalseVal,
InstCombiner::BuilderTy &Builder) {
static Value *foldSelectICmpAndBinOp(Value *CondVal, Value *TrueVal,
Value *FalseVal,
InstCombiner::BuilderTy &Builder) {
// Only handle integer compares. Also, if this is a vector select, we need a
// vector compare.
if (!TrueVal->getType()->isIntOrIntVectorTy() ||
TrueVal->getType()->isVectorTy() != IC->getType()->isVectorTy())
TrueVal->getType()->isVectorTy() != CondVal->getType()->isVectorTy())
return nullptr;

Value *CmpLHS = IC->getOperand(0);
Value *CmpRHS = IC->getOperand(1);

unsigned C1Log;
bool NeedAnd = false;
CmpInst::Predicate Pred = IC->getPredicate();
if (IC->isEquality()) {
if (!match(CmpRHS, m_Zero()))
return nullptr;
CmpPredicate Pred;
Value *CmpLHS, *CmpRHS;

const APInt *C1;
if (!match(CmpLHS, m_And(m_Value(), m_Power2(C1))))
return nullptr;
if (match(CondVal, m_ICmp(Pred, m_Value(CmpLHS), m_Value(CmpRHS)))) {
if (ICmpInst::isEquality(Pred)) {
if (!match(CmpRHS, m_Zero()))
return nullptr;

C1Log = C1->logBase2();
} else {
auto Res = decomposeBitTestICmp(CmpLHS, CmpRHS, Pred);
if (!Res || !Res->Mask.isPowerOf2())
return nullptr;
const APInt *C1;
if (!match(CmpLHS, m_And(m_Value(), m_Power2(C1))))
return nullptr;

CmpLHS = Res->X;
Pred = Res->Pred;
C1Log = Res->Mask.logBase2();
NeedAnd = true;
C1Log = C1->logBase2();
} else {
auto Res = decomposeBitTestICmp(CmpLHS, CmpRHS, Pred);
if (!Res || !Res->Mask.isPowerOf2())
return nullptr;

CmpLHS = Res->X;
Pred = Res->Pred;
C1Log = Res->Mask.logBase2();
NeedAnd = true;
}
} else if (auto *Trunc = dyn_cast<TruncInst>(CondVal)) {
CmpLHS = Trunc->getOperand(0);
C1Log = 0;
Pred = ICmpInst::ICMP_NE;
NeedAnd = !Trunc->hasNoUnsignedWrap();
} else {
return nullptr;
}

Value *Y, *V = CmpLHS;
Expand Down Expand Up @@ -808,7 +816,7 @@ static Value *foldSelectICmpAndBinOp(const ICmpInst *IC, Value *TrueVal,

// Make sure we don't create more instructions than we save.
if ((NeedShift + NeedXor + NeedZExtTrunc + NeedAnd) >
(IC->hasOneUse() + BinOp->hasOneUse()))
(CondVal->hasOneUse() + BinOp->hasOneUse()))
return nullptr;

if (NeedAnd) {
Expand Down Expand Up @@ -1986,9 +1994,6 @@ Instruction *InstCombinerImpl::foldSelectInstWithICmp(SelectInst &SI,
if (Instruction *V = foldSelectZeroOrOnes(ICI, TrueVal, FalseVal, Builder))
return V;

if (Value *V = foldSelectICmpAndBinOp(ICI, TrueVal, FalseVal, Builder))
return replaceInstUsesWith(SI, V);

if (Value *V = foldSelectICmpLshrAshr(ICI, TrueVal, FalseVal, Builder))
return replaceInstUsesWith(SI, V);

Expand Down Expand Up @@ -3946,6 +3951,9 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
if (Instruction *Result = foldSelectInstWithICmp(SI, ICI))
return Result;

if (Value *V = foldSelectICmpAndBinOp(CondVal, TrueVal, FalseVal, Builder))
return replaceInstUsesWith(SI, V);

if (Instruction *Add = foldAddSubSelect(SI, Builder))
return Add;
if (Instruction *Add = foldOverflowingAddSubSelect(SI, Builder))
Expand Down
29 changes: 14 additions & 15 deletions llvm/test/Transforms/InstCombine/select-with-bitwise-ops.ll
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Expand Up @@ -1754,9 +1754,9 @@ define i8 @select_icmp_eq_and_1_0_lshr_tv(i8 %x, i8 %y) {

define i8 @select_trunc_or_2(i8 %x, i8 %y) {
; CHECK-LABEL: @select_trunc_or_2(
; CHECK-NEXT: [[TRUNC:%.*]] = trunc i8 [[X:%.*]] to i1
; CHECK-NEXT: [[OR:%.*]] = or i8 [[Y:%.*]], 2
; CHECK-NEXT: [[SELECT:%.*]] = select i1 [[TRUNC]], i8 [[OR]], i8 [[Y]]
; CHECK-NEXT: [[TMP1:%.*]] = shl i8 [[X:%.*]], 1
; CHECK-NEXT: [[TMP2:%.*]] = and i8 [[TMP1]], 2
; CHECK-NEXT: [[SELECT:%.*]] = or i8 [[Y:%.*]], [[TMP2]]
; CHECK-NEXT: ret i8 [[SELECT]]
;
%trunc = trunc i8 %x to i1
Expand All @@ -1767,9 +1767,9 @@ define i8 @select_trunc_or_2(i8 %x, i8 %y) {

define i8 @select_not_trunc_or_2(i8 %x, i8 %y) {
; CHECK-LABEL: @select_not_trunc_or_2(
; CHECK-NEXT: [[TRUNC:%.*]] = trunc i8 [[X:%.*]] to i1
; CHECK-NEXT: [[OR:%.*]] = or i8 [[Y:%.*]], 2
; CHECK-NEXT: [[SELECT:%.*]] = select i1 [[TRUNC]], i8 [[OR]], i8 [[Y]]
; CHECK-NEXT: [[TMP1:%.*]] = shl i8 [[X:%.*]], 1
; CHECK-NEXT: [[TMP2:%.*]] = and i8 [[TMP1]], 2
; CHECK-NEXT: [[SELECT:%.*]] = or i8 [[Y:%.*]], [[TMP2]]
; CHECK-NEXT: ret i8 [[SELECT]]
;
%trunc = trunc i8 %x to i1
Expand All @@ -1781,9 +1781,8 @@ define i8 @select_not_trunc_or_2(i8 %x, i8 %y) {

define i8 @select_trunc_nuw_or_2(i8 %x, i8 %y) {
; CHECK-LABEL: @select_trunc_nuw_or_2(
; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw i8 [[X:%.*]] to i1
; CHECK-NEXT: [[OR:%.*]] = or i8 [[Y:%.*]], 2
; CHECK-NEXT: [[SELECT:%.*]] = select i1 [[TRUNC]], i8 [[OR]], i8 [[Y]]
; CHECK-NEXT: [[TMP1:%.*]] = shl i8 [[X:%.*]], 1
; CHECK-NEXT: [[SELECT:%.*]] = or i8 [[Y:%.*]], [[TMP1]]
; CHECK-NEXT: ret i8 [[SELECT]]
;
%trunc = trunc nuw i8 %x to i1
Expand All @@ -1794,9 +1793,9 @@ define i8 @select_trunc_nuw_or_2(i8 %x, i8 %y) {

define i8 @select_trunc_nsw_or_2(i8 %x, i8 %y) {
; CHECK-LABEL: @select_trunc_nsw_or_2(
; CHECK-NEXT: [[TRUNC:%.*]] = trunc nsw i8 [[X:%.*]] to i1
; CHECK-NEXT: [[OR:%.*]] = or i8 [[Y:%.*]], 2
; CHECK-NEXT: [[SELECT:%.*]] = select i1 [[TRUNC]], i8 [[OR]], i8 [[Y]]
; CHECK-NEXT: [[TMP1:%.*]] = shl i8 [[X:%.*]], 1
; CHECK-NEXT: [[TMP2:%.*]] = and i8 [[TMP1]], 2
; CHECK-NEXT: [[SELECT:%.*]] = or i8 [[Y:%.*]], [[TMP2]]
; CHECK-NEXT: ret i8 [[SELECT]]
;
%trunc = trunc nsw i8 %x to i1
Expand All @@ -1807,9 +1806,9 @@ define i8 @select_trunc_nsw_or_2(i8 %x, i8 %y) {

define <2 x i8> @select_trunc_or_2_vec(<2 x i8> %x, <2 x i8> %y) {
; CHECK-LABEL: @select_trunc_or_2_vec(
; CHECK-NEXT: [[TRUNC:%.*]] = trunc <2 x i8> [[X:%.*]] to <2 x i1>
; CHECK-NEXT: [[OR:%.*]] = or <2 x i8> [[Y:%.*]], splat (i8 2)
; CHECK-NEXT: [[SELECT:%.*]] = select <2 x i1> [[TRUNC]], <2 x i8> [[OR]], <2 x i8> [[Y]]
; CHECK-NEXT: [[TMP1:%.*]] = shl <2 x i8> [[X:%.*]], splat (i8 1)
; CHECK-NEXT: [[TMP2:%.*]] = and <2 x i8> [[TMP1]], splat (i8 2)
; CHECK-NEXT: [[SELECT:%.*]] = or <2 x i8> [[Y:%.*]], [[TMP2]]
; CHECK-NEXT: ret <2 x i8> [[SELECT]]
;
%trunc = trunc <2 x i8> %x to <2 x i1>
Expand Down