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.
--
H.J.
From 6606ec5573e724295bdceb572ddc2813f021709f Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <[email protected]>
Date: Fri, 7 Feb 2025 13:49:30 +0800
Subject: [PATCH] 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 <[email protected]>
---
gcc/testsuite/gcc.target/i386/pr111673.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/gcc/testsuite/gcc.target/i386/pr111673.c b/gcc/testsuite/gcc.target/i386/pr111673.c
index 8d8a5a764f0..b9ceacf7651 100644
--- a/gcc/testsuite/gcc.target/i386/pr111673.c
+++ b/gcc/testsuite/gcc.target/i386/pr111673.c
@@ -1,5 +1,19 @@
/* { dg-do compile { target { ! ia32 } } } */
/* { dg-options "-O2 -fdump-rtl-pro_and_epilogue" } */
+/* Keep labels and directives ('.cfi_startproc', '.cfi_endproc'). */
+/* { dg-final { check-function-bodies "**" "" "" { target "*-*-*" } {^\t?\.} } } */
+
+/*
+**advance:
+**.LFB0:
+** .cfi_startproc
+** testl %edi, %edi
+** jle .L2
+** imull %edi, %edi
+** leal \(%rdi,%rdi\), %eax
+** ret
+**...
+*/
/* Verify there is an early return without the prolog and shrink-wrap
the function. */
--
2.48.1
