[Bug rtl-optimization/62041] vector fneg codegen uses a subtract instead of an xor (x86-64)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62041

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-08-07
          Component|target                      |rtl-optimization
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
That's because _mm_sub_ps is a builtin during gimple opts and on RTL we
generally don't do very many FP related optimizations (especially on vectors).

Confirmed.

(insn 6 5 7 (set (reg:V4SF 87)
        (mem/u/c:V4SF (symbol_ref/u:DI ("*.LC0") [flags 0x2]) [2  S16 A128]))
/usr/lib64/gcc/x86_64-suse-linux/4.9/include/xmmintrin.h:189 -1
     (expr_list:REG_EQUAL (const_vector:V4SF [
                (const_double:SF -0.0 [-0x0.0p+0])
                (const_double:SF -0.0 [-0x0.0p+0])
                (const_double:SF -0.0 [-0x0.0p+0])
                (const_double:SF -0.0 [-0x0.0p+0])
            ])
        (nil)))

(insn 7 6 8 (set (reg:V4SF 86)
        (minus:V4SF (reg:V4SF 87)
            (reg/v:V4SF 85 [ x ])))
/usr/lib64/gcc/x86_64-suse-linux/4.9/include/xmmintrin.h:189 -1
     (nil))

could be optimized guarded with the appropriate flags (signed zeros?
nans/infs?).