[LLVMbugs] [Bug 18532] Multiplication of a float vector by -1 should be transformed to an XOR of sign bits.

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sat Jan 18 08:47:22 PST 2014


http://llvm.org/bugs/show_bug.cgi?id=18532

Benjamin Kramer <benny.kra at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |benny.kra at gmail.com
         Resolution|---                         |FIXED

--- Comment #1 from Benjamin Kramer <benny.kra at gmail.com> ---
With r199553:

$ cat mul.c
#include <immintrin.h>

__m128 foo(__m128 x) {
  return _mm_mul_ps(x, _mm_set1_ps(-1.0f));
}

$ clang -O -S -o - mul.c
[...]                                                                    
LCPI0_0:
    .long    2147483648              ## float -0.000000e+00
    .long    2147483648              ## float -0.000000e+00
    .long    2147483648              ## float -0.000000e+00
    .long    2147483648              ## float -0.000000e+00
[...]
    xorps    LCPI0_0(%rip), %xmm0

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