[Bug tree-optimization/51062] SLP vectorization of dot (inner) product

[vincenzo.innocente at cern dot ch]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51062

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|4.7.0                       |4.8.0

--- Comment #3 from vincenzo Innocente <vincenzo.innocente at cern dot ch> 
2012-11-30 13:53:41 UTC ---
in 4.8 using 
typedef float __attribute__( ( vector_size( 16 ) ) ) float32x4_t;
typedef double __attribute__( ( vector_size( 32 ) ) ) float64x4_t;
the scalar product works well IF WRITTEN as a loop!

in the following 
dot_product2 produces exactly the code I would have expected to be emitted by
"dot_product"..
would be nice to have also the reduction of a single vector to emit
horizonal-sum…


float dot_product(float32x4_t x, float32x4_t y) {
  float32x4_t res = x*y;
  float ret=0;
  for (int i=0;i!=4;++i) ret+=res[i];
  return ret;
}

float dot_product2(float32x4_t x, float32x4_t y) {
  float ret=0;
  for (int i=0;i!=4;++i) ret+=x[i]*y[i];
  return ret;
}


double dot_product(float64x4_t x, float64x4_t y) {
  float64x4_t res = x*y;
  double ret=0;
  for (int i=0;i!=4;++i) ret+=res[i];
  return ret;
}

double dot_product2(float64x4_t x, float64x4_t y) {
  double ret=0;
  for (int i=0;i!=4;++i) ret+=x[i]*y[i];
  return ret;
}

c++ -Ofast -ftree-vectorizer-verbose=2 -S cross.cc  -march=corei7-avx; cat
cross.s | c++filt
dot_product(float __vector, float __vector):
LFB2:
    vmulps    %xmm1, %xmm0, %xmm1
    vmovaps    %xmm1, %xmm0
    vshufps    $85, %xmm1, %xmm1, %xmm2
    vaddss    %xmm0, %xmm2, %xmm0
    vunpckhps    %xmm1, %xmm1, %xmm2
    vshufps    $255, %xmm1, %xmm1, %xmm1
    vaddss    %xmm2, %xmm0, %xmm0
    vaddss    %xmm1, %xmm0, %xmm0
    ret
LFE2:
    .align 4,0x90
    .globl dot_product2(float __vector, float __vector)
dot_product2(float __vector, float __vector):
LFB3:
    vmulps    %xmm0, %xmm1, %xmm1
    vhaddps    %xmm1, %xmm1, %xmm0
    vhaddps    %xmm0, %xmm0, %xmm0
    ret
LFE3:
    .align 4,0x90
    .globl dot_product(double __vector, double __vector)
dot_product(double __vector, double __vector):
LFB4:
    vmulpd    %ymm1, %ymm0, %ymm1
    vmovapd    %xmm1, %xmm0
    vextractf128    $0x1, %ymm1, %xmm1
    vhaddpd    %xmm0, %xmm0, %xmm0
    vmovapd    %xmm1, %xmm2
    vunpckhpd    %xmm1, %xmm1, %xmm1
    vaddsd    %xmm2, %xmm0, %xmm0
    vaddsd    %xmm1, %xmm0, %xmm0
    vzeroupper
    ret
LFE4:
    .align 4,0x90
    .globl dot_product2(double __vector, double __vector)
dot_product2(double __vector, double __vector):
LFB5:
    vmulpd    %ymm0, %ymm1, %ymm1
    vhaddpd    %ymm1, %ymm1, %ymm1
    pushq    %rbp
LCFI0:
    movq    %rsp, %rbp
LCFI1:
    andq    $-32, %rsp
    addq    $16, %rsp
    vperm2f128    $1, %ymm1, %ymm1, %ymm0
    vaddpd    %ymm0, %ymm1, %ymm1
    vmovapd    %xmm1, %xmm0
    vzeroupper
    leave
LCFI2:
    ret