[Bug tree-optimization/50713] SLP vs loop: code generated differs (SLP less efficient)

["vincenzo.innocente at cern dot ch" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50713

vincenzo Innocente <vincenzo.innocente at cern dot ch> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|SLP vs loop: code generated |SLP vs loop: code generated
                   |differs                     |differs (SLP less
                   |                            |efficient)

--- Comment #5 from vincenzo Innocente <vincenzo.innocente at cern dot ch> 2012-10-25 13:19:23 UTC ---
I think that here the problem is similar
using 4.8 trunk

in the following code the explicit  loop is way more efficient that the vector
notation
for all corei7, corei7-avx and bdver1 architectures.
(i spare you the assembler dumps. Inferring the number of instructions from nm
should enough
0000000000000170 T dfmav(double __vector, double __vector, double __vector,
double, double)
0000000000000370 T dfmal(double __vector, double __vector, double __vector,
double, double)
00000000000003c0 T dfma8v(double __vector, double __vector, double __vector,
double, double)
0000000000000810 T dfma8l(double __vector, double __vector, double __vector,
double, double)
00000000000008b0 short EH_frame1
)


typedef double __attribute__( ( vector_size( 32 ) ) ) float64x4_t;
typedef double __attribute__( ( vector_size( 64 ) ) ) float64x8_t;
float64x4_t dfmav(float64x4_t x, float64x4_t y, float64x4_t z, double a, double
b) {
    return a*x*(y+b*z); 
}

float64x4_t dfmal(float64x4_t x, float64x4_t y, float64x4_t z, double a, double
b) {
        float64x4_t r;
        for (int i=0; i!=4;++i)
          r[i] = a*x[i]*(y[i]+b*z[i]);
       return r;
}

float64x8_t dfma8v(float64x8_t x, float64x8_t y, float64x8_t z, double a,
double b) {
        return a*x*(y+b*z);
}

float64x8_t dfma8l(float64x8_t x, float64x8_t y, float64x8_t z, double a,
double b) {
        float64x8_t r;
        for (int i=0; i!=8;++i)
          r[i] = a*x[i]*(y[i]+b*z[i]);
       return r;
}