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62ad0a5cf3
As noted in the D44909 review, the transform from (fptosi+sitofp) to ftrunc
can produce -0.0 where the original code does not:
#include <stdio.h>
int main(int argc) {
float x;
x = -0.8 * argc;
printf("%f\n", (float)((int)x));
return 0;
}
$ clang -O0 -mavx fp.c ; ./a.out
0.000000
$ clang -O1 -mavx fp.c ; ./a.out
-0.000000
Ideally, we'd use IR/node flags to predicate the transform, but the IR parser
doesn't currently allow fast-math-flags on the cast instructions. So for now,
just use the function attribute that corresponds to clang's "-fno-signed-zeros"
option.
Differential Revision: https://reviews.llvm.org/D48085
llvm-svn: 335761
46 lines
1.1 KiB
LLVM
46 lines
1.1 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
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; RUN: llc -mtriple=aarch64-unknown-unknown < %s | FileCheck %s
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define float @trunc_unsigned_f32(float %x) #0 {
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; CHECK-LABEL: trunc_unsigned_f32:
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; CHECK: // %bb.0:
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; CHECK-NEXT: frintz s0, s0
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; CHECK-NEXT: ret
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%i = fptoui float %x to i32
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%r = uitofp i32 %i to float
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ret float %r
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}
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define double @trunc_unsigned_f64(double %x) #0 {
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; CHECK-LABEL: trunc_unsigned_f64:
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; CHECK: // %bb.0:
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; CHECK-NEXT: frintz d0, d0
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; CHECK-NEXT: ret
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%i = fptoui double %x to i64
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%r = uitofp i64 %i to double
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ret double %r
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}
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define float @trunc_signed_f32(float %x) #0 {
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; CHECK-LABEL: trunc_signed_f32:
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; CHECK: // %bb.0:
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; CHECK-NEXT: frintz s0, s0
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; CHECK-NEXT: ret
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%i = fptosi float %x to i32
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%r = sitofp i32 %i to float
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ret float %r
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}
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define double @trunc_signed_f64(double %x) #0 {
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; CHECK-LABEL: trunc_signed_f64:
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; CHECK: // %bb.0:
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; CHECK-NEXT: frintz d0, d0
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; CHECK-NEXT: ret
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%i = fptosi double %x to i64
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%r = sitofp i64 %i to double
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ret double %r
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}
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attributes #0 = { "no-signed-zeros-fp-math"="true" }
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