[Bug middle-end/31263] Misoptimization of constant function expressions

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2007-03-19 16:47 -------
On x86 different addressing modes and induction variables are used.  Good:

.L2:
        movq    %r12, 8(%rsp)
        addl    $1, %ebp
        movsd   8(%rsp), %xmm0
        call    Square
        movsd   %xmm0, (%rbx)
        addq    $8, %rbx
        cmpl    $50000000, %ebp
        jne     .L2

bad:

.L2:
        movq    %r12, 8(%rsp)
        movsd   8(%rsp), %xmm0
        call    Square 
        movsd   %xmm0, (%rbp,%rbx,8)
        addq    $1, %rbx
        cmpq    $50000000, %rbx
        jne     .L2

this is because we retain the complex expression until the last DOM run
after loop optimization (for 4.1.2 at least).


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31263