GCC cannot move address calculation to store+load?

[Miles Bader]

Richard Biener <richard.guenther@gmail.com> writes:
> Note that combine does not apply because %eax is used multiple
> times.  This also means that for code-size the combining is not a good
> idea.

Though the lea instruction seems rather large, so in fact the code is
a fair bit smaller without it, e.g. as generated by clang/llvm:

clang/llvm 3.1 (-O2 -m32):

00000000 <foo>:
   0:	8b 44 24 08          	mov    0x8(%esp),%eax
   4:	8b 4c 24 04          	mov    0x4(%esp),%ecx
   8:	8b 14 c1             	mov    (%ecx,%eax,8),%edx
   b:	89 15 00 00 00 00    	mov    %edx,0x0
  11:	89 04 c1             	mov    %eax,(%ecx,%eax,8)
  14:	31 c0                	xor    %eax,%eax
  16:	c3                   	ret    

gcc 4.8 20130113 (-O2 -m32):

00000000 <foo>:
   0:	8b 54 24 08          	mov    0x8(%esp),%edx
   4:	8d 04 d5 00 00 00 00 	lea    0x0(,%edx,8),%eax
   b:	03 44 24 04          	add    0x4(%esp),%eax
   f:	8b 08                	mov    (%eax),%ecx
  11:	89 0d 00 00 00 00    	mov    %ecx,0x0
  17:	89 10                	mov    %edx,(%eax)
  19:	31 c0                	xor    %eax,%eax
  1b:	c3                   	ret    

-miles

-- 
Ich bin ein Virus. Mach' mit und kopiere mich in Deine .signature.