[Bug rtl-optimization/21182] gcc can use registers but uses stack instead

["vda at port dot imtp dot ilyichevsk dot odessa dot ua" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From vda at port dot imtp dot ilyichevsk dot odessa dot ua  2005-04-24 13:05 -------
With 4.0.0: gcc -O2 gives the same result as gcc -O3,
which is better than gcc 3.4.3 -O2 but worse than 3.4.3 -O3.
For example:

        movl    %edx, -20(%ebp)
        orl     %ecx, %edi
        movl    %ebx, %esi
        xorl    %ecx, %esi
        andl    %eax, %ebx
        xorl    %edi, %ebx
        movl    %eax, %ecx
        notl    %ecx
        xorl    %ebx, %ecx
        orl     %edi, %eax
        xorl    %eax, %esi
        rorl    $19, %esi
        rorl    $29, -20(%ebp)
        xorl    %esi, %ebx
        xorl    -20(%ebp), %ecx
        xorl    -20(%ebp), %ebx
        rorl    $31, %ebx
        leal    0(,%esi,8), %edx

1) Why %edx was stored in -20(%ebp), there is no %edx usage
in the following insns. %edx value could stay in register
and we can continue to work on its value in register.
2) rorl $31, %ebx == roll $1, %ebx, but 1 bit roll insn is
smaller.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21182