Jie Zhang wrote:
> typedef unsigned short u16;
> typedef unsigned int u32;
>
> u32 a(volatile u16* off) {
> return *off;
> }
> mingw32-gcc-4.3.0.exe -c -O2 -fomit-frame-pointer -mtune=core2 test.c
>
> it produces:
> 00000000 <_a>:
> 0: 8b 44 24 04 mov 0x4(%esp),%eax
> 4: 0f b7 00 movzwl (%eax),%eax
> 7: 0f b7 c0 movzwl %ax,%eax <== The redundant insn
> a: c3 ret
How does it look at the RTL level? I wonder if this situation is similar to
the one being discussed in the other current thread "Which optimizer should
remove redundant subreg of sign_extension?"
cheers,
DaveK
