------- Comment #1 from tkho at ucla dot edu 2005-11-18 02:35 -------
Created an attachment (id=10273)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=10273&action=view)
shift/mask long long testcase
Here is a rough instruction-count comparison for f() compiled at -O2,
march=pentiumpro between icc9 and gcc head 20051108 with the patch in PR 17886,
comment #16:
icc: 11
gcc: 23
`icc -O2 -march=pentiumpro -S test3.c` gives:
movl 4(%esp), %eax
movl 8(%esp), %ecx
movl %eax, %edx
shrl $24, %edx
shll $8, %eax
shll $8, %ecx
orl %ecx, %edx
movzwl 18(%esp), %ecx
movzbl %cl, %ecx
orl %ecx, %eax
ret
`gcc -c test3.c -save-temps -O2 -march=pentiumpro -momit-leaf-frame-pointer`
gives:
subl $12, %esp
movl %edi, 8(%esp)
movl 28(%esp), %edi
movl 16(%esp), %eax
movl 20(%esp), %edx
movl %esi, 4(%esp)
movl 24(%esp), %esi
movl %edi, %esi
xorl %edi, %edi
movl 8(%esp), %edi
movl %ebx, (%esp)
shrl $16, %esi
xorl %ebx, %ebx
shldl $8, %eax, %edx
movl %esi, %ecx
movl 4(%esp), %esi
orl %ebx, %edx
movl (%esp), %ebx
andl $255, %ecx
sall $8, %eax
addl $12, %esp
orl %ecx, %eax
ret
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
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24929
