[Bug middle-end/23181] [4.1 Regression] Slowdown of the bresenham line drawing by roughly 20%

[steven at gcc dot gnu dot org]

------- Comment #21 from steven at gcc dot gnu dot org  2006-01-07 18:23 -------
Using ``.ident  "GCC: (GNU) 4.1.0 20060107 (prerelease)"'' on AMD64 with -m32,
I get the following assembly outputs:

options: -O2 -fno-tree-dominator-opts
.L2:
        movl    $videoram, %eax
        movl    $-2, %edx
        jmp     .L5
        .p2align 4,,7
.L14:
        addl    $18, %edx
.L5:
        testl   %edx, %edx
        movb    $5, (%eax)
        js      .L6
        addl    $21, %eax
        subl    $40, %edx
.L6:
        incl    %eax
        cmpl    %eax, %ecx
        jne     .L14
        incl    %ebx
        movb    $5, videoram+209
        cmpl    $10000000, %ebx
        jne     .L2

options: -O2
.L2:
        movb    $5, videoram
        movl    $videoram, %eax
        movl    $-2, %edx
.L18:
        incl    %eax
        cmpl    %eax, %ecx
        je      .L20
        .p2align 4,,7
.L5:
        addl    $18, %edx
        movb    $5, (%eax)
        js      .L18
        addl    $21, %eax
        subl    $40, %edx
        incl    %eax
        cmpl    %eax, %ecx
        jne     .L5
.L20:
        incl    %ebx
        movb    $5, videoram+209
        cmpl    $10000000, %ebx
        jne     .L2


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23181