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[InstCombine] fold ldexp(x, zext(i1 y)) to fmul x, (select y, 2.0, 1.0) #94887

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Merged
arsenm merged 5 commits into from
Jun 10, 2024
Merged

[InstCombine] fold ldexp(x, zext(i1 y)) to fmul x, (select y, 2.0, 1.0) #94887

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00af1fb
ldexp(x, zext(i1 y))
c8ef Jun 9, 2024
fb274bb
address CR comments
c8ef Jun 9, 2024
edc40e4
remove useless icmp
c8ef Jun 9, 2024
270482c
preserve fast math flag; add test about it
c8ef Jun 9, 2024
5caee72
fix test
c8ef Jun 10, 2024
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10 changes: 10 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2618,6 +2618,16 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
}
}

// ldexp(x, zext(i1 y)) -> fmul x, (select y, 2.0, 1.0)
Value *ExtSrc;
if (match(Exp, m_ZExt(m_Value(ExtSrc))) &&
ExtSrc->getType()->getScalarSizeInBits() == 1) {
Value *Select =
Builder.CreateSelect(ExtSrc, ConstantFP::get(II->getType(), 2.0),
ConstantFP::get(II->getType(), 1.0));
return BinaryOperator::CreateFMulFMF(Src, Select, II);
}

break;
}
case Intrinsic::ptrauth_auth:
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57 changes: 57 additions & 0 deletions llvm/test/Transforms/InstCombine/ldexp-zext.ll
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@@ -0,0 +1,57 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=instcombine -S | FileCheck %s

define float @ldexp_zext_float(float %x, i1 %bool) {
; CHECK-LABEL: @ldexp_zext_float(
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[BOOL:%.*]], float 2.000000e+00, float 1.000000e+00
; CHECK-NEXT: [[LDEXP:%.*]] = fmul float [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret float [[LDEXP]]
;
%zext = zext i1 %bool to i32
%ldexp = call float @llvm.ldexp.f32.i32(float %x, i32 %zext)
ret float %ldexp
}

define float @ldexp_zext_float_negative(float %x, i8 %y) {
; CHECK-LABEL: @ldexp_zext_float_negative(
; CHECK-NEXT: [[ZEXT:%.*]] = zext i8 [[Y:%.*]] to i32
; CHECK-NEXT: [[LDEXP:%.*]] = call float @llvm.ldexp.f32.i32(float [[X:%.*]], i32 [[ZEXT]])
; CHECK-NEXT: ret float [[LDEXP]]
;
%zext = zext i8 %y to i32
%ldexp = call float @llvm.ldexp.f32.i32(float %x, i32 %zext)
ret float %ldexp
}

define double @ldexp_zext_double(double %x, i1 %bool) {
; CHECK-LABEL: @ldexp_zext_double(
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[BOOL:%.*]], double 2.000000e+00, double 1.000000e+00
; CHECK-NEXT: [[LDEXP:%.*]] = fmul double [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret double [[LDEXP]]
;
%zext = zext i1 %bool to i32
%ldexp = call double @llvm.ldexp.f32.i32(double %x, i32 %zext)
ret double %ldexp
}

define double @ldexp_zext_double_fast_math(double %x, i1 %bool) {
; CHECK-LABEL: @ldexp_zext_double_fast_math(
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[BOOL:%.*]], double 2.000000e+00, double 1.000000e+00
; CHECK-NEXT: [[LDEXP:%.*]] = fmul fast double [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret double [[LDEXP]]
;
%zext = zext i1 %bool to i32
%ldexp = call fast double @llvm.ldexp.f32.i32(double %x, i32 %zext)
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@dtcxzyw dtcxzyw Jun 9, 2024

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Don't use fast here. See https://llvm.org/docs/InstCombineContributorGuide.html#flag-tests

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@c8ef c8ef Jun 10, 2024

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Fixed.

ret double %ldexp
}

define <2 x float> @ldexp_zext_float_vector(<2 x float> %x, <2 x i1> %bool) {
; CHECK-LABEL: @ldexp_zext_float_vector(
; CHECK-NEXT: [[TMP1:%.*]] = select <2 x i1> [[BOOL:%.*]], <2 x float> <float 2.000000e+00, float 2.000000e+00>, <2 x float> <float 1.000000e+00, float 1.000000e+00>
; CHECK-NEXT: [[LDEXP:%.*]] = fmul <2 x float> [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret <2 x float> [[LDEXP]]
;
%zext = zext <2 x i1> %bool to <2 x i32>
%ldexp = call <2 x float> @llvm.ldexp.v2f32.v2i32(<2 x float> %x, <2 x i32> %zext)
ret <2 x float> %ldexp
}