[llvm-bugs] [Bug 39479] New: Failure to simplify select(-1, +1, cond)*b -> select(-b, b, cond)

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=39479

            Bug ID: 39479
           Summary: Failure to simplify select(-1,+1,cond)*b ->
                    select(-b,b,cond)
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm-dev at redking.me.uk
                CC: filcab at gmail.com, llvm-bugs at lists.llvm.org,
                    spatel+llvm at rotateright.com, tilkax at gmail.com

#include <math.h>

int sel_mul_s32(bool a, int b)
{
    return (a ? -1 : 1) * b;
}

float sel_mul_f32(bool a, float b)
{
    return (a ? -1 : 1) * b;
}

https://godbolt.org/z/nGT8f_

clang:

_Z11sel_mul_s32bi: # @_Z11sel_mul_s32bi
  xorb $1, %dil
  movzbl %dil, %eax
  leal -1(%rax,%rax), %eax
  imull %esi, %eax
  retq


_Z11sel_mul_f32bf: # @_Z11sel_mul_f32bf
  testl %edi, %edi
  jne .LBB1_1
  vmovss .LCPI1_1(%rip), %xmm1 # xmm1 = mem[0],zero,zero,zero
  vmulss %xmm0, %xmm1, %xmm0
  retq
.LBB1_1:
  vmovss .LCPI1_0(%rip), %xmm1 # xmm1 = mem[0],zero,zero,zero
  vmulss %xmm0, %xmm1, %xmm0
  retq

gcc:

_Z11sel_mul_s32bi:
  testb %dil, %dil
  movl %esi, %eax
  je .L6
  negl %eax
.L6:
  ret

_Z11sel_mul_f32bf:
  testb %dil, %dil
  je .L13
  vxorps .LC0(%rip), %xmm0, %xmm0
.L13:
  ret

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