https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94789
Wilco <wilco at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |wilco at gcc dot gnu.org
--- Comment #4 from Wilco <wilco at gcc dot gnu.org> ---
(In reply to Gabriel Ravier from comment #0)
> int r(int x, unsigned b)
> {
> int const m = CHAR_BIT * sizeof(x) - b;
> return (x << m);
> }
>
> `CHAR_BIT * sizeof(x) - b;` can be optimized to `-b`. LLVM does this
> transformation, not GCC.
>
> Comparison here : https://godbolt.org/z/5byJ2E
AArch64 already generates:
neg w1, w1
lsl w0, w0, w1
ret
