[Bug target/19923] openssl is slower when compiled with gcc 4.0 than 3.3

["rakdver at atrey dot karlin dot mff dot cuni dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From rakdver at atrey dot karlin dot mff dot cuni dot cz  2005-06-02 08:01 -------
Subject: Re:  openssl is slower when compiled with gcc 4.0 than 3.3

The assembler attributed to 4.0 was produced by mainline (or some
patched version of 4.0), wasn't it?
Otherwise I cannot imagine why the inner loop would be unrolled.

For plain 4.0, we get the following code, which seems just fine
and equivalent to the one obtained with 3.4 (one of the memory
references is strength reduced, but since we still fit into registers,
this is OK).

I don't just now see what/whether there is some problem with the code
produced by 4.1, but I also don't see anything related to addressing
mode selection there.

.L21:
        movl    S@GOTOFF(%ebx,%eax,4), %eax
        xorl    (%edx), %eax
        movl    %eax, (%edx)
        movl    S@GOTOFF(%ebx,%eax,4), %eax
        xorl    4(%edx), %eax
        movl    %eax, 4(%edx)
        movl    S@GOTOFF(%ebx,%eax,4), %eax
        xorl    8(%edx), %eax
        movl    %eax, 8(%edx)
        movl    S@GOTOFF(%ebx,%eax,4), %eax
        xorl    12(%edx), %eax
        movl    %eax, 12(%edx)
        movl    S@GOTOFF(%ebx,%eax,4), %eax
        xorl    16(%edx), %eax
        movl    %eax, 16(%edx)
        movl    S@GOTOFF(%ebx,%eax,4), %eax
        xorl    20(%edx), %eax
        movl    %eax, 20(%edx)
        movl    S@GOTOFF(%ebx,%eax,4), %eax
        xorl    24(%edx), %eax
        movl    %eax, 24(%edx)
        movl    S@GOTOFF(%ebx,%eax,4), %eax
        xorl    28(%edx), %eax
        movl    %eax, 28(%edx)
        addl    $32, %edx
        leal    -12(%ebp), %esi
        cmpl    %esi, %edx
        jne     .L21



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19923