x86: Verify that PUSH/POP can be skipped

x86: Verify that PUSH/POP can be skipped

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.

	PR rtl-optimization/111673
	* gcc.target/i386/pr111673.c: Verify that PUSH/POP can be
	skipped.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>