------- Comment #6 from vda dot linux at googlemail dot com 2006-07-30 13:38
-------
Patched versus stock gcc-4.1.1 on this code
unsigned v;
void f9188_mul365384439_shift27(unsigned A) { v = A/(unsigned)1577682821; }
is:
# diff -u suboptimal-411-O2.s suboptimal-411-O2-fixed.s
--- suboptimal-411-O2.s 2006-07-29 19:34:09.000000000 +0200
+++ suboptimal-411-O2-fixed.s 2006-07-29 19:37:14.000000000 +0200
@@ -19,21 +19,10 @@
f9188_mul365384439_shift27:
pushl %ebp
movl %esp, %ebp
- pushl %edi
- pushl %esi
- pushl %ebx
- movl 8(%ebp), %ebx
- movl $1551183727, %ecx
- movl %ebx, %eax
- mull %ecx
- subl %edx, %ebx
- shrl %ebx
- leal (%ebx,%edx), %eax
- shrl $30, %eax
- movl %eax, v
- popl %ebx
- popl %esi
- popl %edi
+ movl $365384439, %eax
+ mull 8(%ebp)
+ shrl $27, %edx
+ movl %edx, v
leave
ret
...
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28417
