On Fri, Feb 7, 2025 at 1:57 PM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> For
>
> ---
> int f(int);
>
> int advance(int dz)
> {
> if (dz > 0)
> return (dz + dz) * dz;
> else
> return dz * f(dz);
> }
> ---
>
> Before r15-1619-g3b9b8d6cfdf593
>
> advance(int):
> push rbx
> mov ebx, edi
> test edi, edi
> jle .L2
> imul ebx, edi
> lea eax, [rbx+rbx]
> pop rbx
> ret
> .L2:
> call f(int)
> imul eax, ebx
> pop rbx
> ret
>
> After
>
> advance(int):
> test edi, edi
> jle .L2
> imul edi, edi
> lea eax, [rdi+rdi]
> ret
> .L2:
> sub rsp, 24
> mov DWORD PTR [rsp+12], edi
> call f(int)
> imul eax, DWORD PTR [rsp+12]
> add rsp, 24
> ret
>
> There's no call in if branch, it's not optimal to push rbx at the entry
> of the function, it can be sinked to else branch. When "jle .L2" is not
> taken, it can save one push instruction. Update pr111673.c to verify
> that this optimization isn't turned off.
Ok
>
> PR rtl-optimization/111673
> * gcc.target/i386/pr111673.c: Verify that PUSH/POP can be
> skipped.
>
>
> --
> H.J.
--
BR,
Hongtao
