[Bug tree-optimization/51499] vectorizer missing simple case

["fb.programming at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499

--- Comment #4 from fb.programming at gmail dot com 2011-12-11 11:52:30 UTC ---
Looks like there has been some great progress in gcc 4.7!

Still I think it behaves slightly buggy.

(1) In this case it should work without -funsafe-math-optimizations but
    it doesn't. gcc 4.7 requires -fno-signed-zeros -fno-trapping-math
   -fassociative-math to make it work.

(2) The prediction:
       7: not vectorized: vectorization not profitable.
    is just wrong. Forcing it with -fno-vect-cost-model shows it speeds up
    by factor of 2.

(3) If I change all double's into float's in the code above it seems to
    work without forcing it (-fno-vect-cost-model):


   g++-4.7 -S -Wall -O2  -ftree-vectorize -ftree-vectorizer-verbose=2 \
           -funsafe-math-optimizations test.cpp

   Analyzing loop at test.cpp:7


   Vectorizing loop at test.cpp:7

   7: vectorizing stmts using SLP.
   7: LOOP VECTORIZED.
   test.cpp:4: note: vectorized 1 loops in function.


    However, it hasn't vectorized it at all as the assembly shows:

.L11:
    addq    $1, %rax
    addss    %xmm0, %xmm3
    cmpq    %rax, %rdi
    addss    %xmm0, %xmm4
    addss    %xmm0, %xmm7
    addss    %xmm0, %xmm6
    addss    %xmm0, %xmm5
    addss    %xmm0, %xmm1
    ja    .L11