[Bug middle-end/17886] variable rotate and long long rotate should be better optimized

[tkho at ucla dot edu]

------- Comment #24 from tkho at ucla dot edu  2005-11-11 01:26 -------
For comparison, here's the code from gcc 2.95.3. It generates the same 18
instructions for both march=i386 and march=pentiumpro.
`gcc -c test3.c -save-temps -O2 -momit-leaf-frame-pointer -march=pentiumpro`:
        pushl %ebx
        movl 8(%esp),%ecx
        movl 12(%esp),%ebx
        movl 16(%esp),%eax
        movl 20(%esp),%edx
        shldl $8,%ecx,%ebx
        sall $8,%ecx
        movl %edx,%eax
        xorl %edx,%edx
        shrl $16,%eax
        andl $255,%eax
        andl $0,%edx
        orl %eax,%ecx
        orl %edx,%ebx
        movl %ecx,%eax
        movl %ebx,%edx
        popl %ebx
        ret

Also, in comment #23, I erronously used g++. Luckily, the same code was
generated with gcc.

On another note, Mark, I tried your patch in comment #10. I grabbed gcc-head
from 2005-09-28 and compared a clean build with a build that had your patches
applied. There was no difference in the assembly for the test case in comment
#23, and there was no performance gain in our benchmark application.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17886