https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113912
Bug ID: 113912
Summary: push2/pop2 generated when stack isn't aligned to 16
bytes
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: hjl.tools at gmail dot com
CC: crazylht at gmail dot com
Target Milestone: ---
Target: x86-64
[hjl@gnu-cfl-3 apx-1]$ cat x.c
extern int bar (int);
void foo ()
{
int a,b,c,d,e,f,i;
a = bar (5);
b = bar (a);
c = bar (b);
d = bar (c);
e = bar (d);
f = bar (e);
for (i = 1; i < 10; i++)
{
a += bar (a + i) + bar (b + i) +
bar (c + i) + bar (d + i) +
bar (e + i) + bar (f + i);
}
}
[hjl@gnu-cfl-3 apx-1]$ make
/export/build/gnu/tools-build/gcc-gitlab-debug/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/tools-build/gcc-gitlab-debug/build-x86_64-linux/gcc/ -mapxf
-O2 -mpreferred-stack-boundary=3 -fomit-frame-pointer -S x.c
[hjl@gnu-cfl-3 apx-1]$ cat x.s
.file "x.c"
.text
.p2align 4
.globl foo
.type foo, @function
foo:
.LFB0:
.cfi_startproc
pushp %r15
.cfi_def_cfa_offset 16
.cfi_offset 15, -16
movl $5, %edi
push2p %r13, %r14
.cfi_def_cfa_offset 32
.cfi_offset 14, -24
.cfi_offset 13, -32
push2p %rbp, %r12
.cfi_def_cfa_offset 48
.cfi_offset 12, -40
.cfi_offset 6, -48
pushp %rbx
.cfi_def_cfa_offset 56
.cfi_offset 3, -56
movl $1, %ebx
subq $8, %rsp
.cfi_def_cfa_offset 64
call bar
movl %eax, %edi
movl %eax, %r12d
call bar
movl %eax, %edi
movl %eax, %r15d
call bar
movl %eax, %edi
movl %eax, %r14d
call bar
movl %eax, %edi
movl %eax, %r13d
call bar
movl %eax, %edi
movl %eax, (%rsp)
call bar
movl %eax, 4(%rsp)
.p2align 4,,10
.p2align 3
.L2:
leal (%r12,%rbx), %edi
call bar
leal (%r15,%rbx), %edi
movl %eax, %ebp
call bar
leal (%r14,%rbx), %edi
addl %eax, %ebp
call bar
leal 0(%r13,%rbx), %edi
addl %eax, %ebp
call bar
addl %ebx, (%rsp), %edi
addl %eax, %ebp
call bar
addl %ebx, 4(%rsp), %edi
addl $1, %ebx
addl %eax, %ebp
call bar
addl %eax, %ebp
addl %ebp, %r12d
cmpl $10, %ebx
jne .L2
addq $8, %rsp
.cfi_def_cfa_offset 56
popp %rbx
.cfi_def_cfa_offset 48
pop2p %r12, %rbp
.cfi_restore 12
.cfi_restore 6
.cfi_def_cfa_offset 32
pop2p %r14, %r13
.cfi_restore 14
.cfi_restore 13
.cfi_def_cfa_offset 16
popp %r15
.cfi_def_cfa_offset 8
ret
.cfi_endproc
.LFE0:
.size foo, .-foo
.ident "GCC: (GNU) 14.0.1 20240213 (experimental)"
.section .note.GNU-stack,"",@progbits
[hjl@gnu-cfl-3 apx-1]$
With -mpreferred-stack-boundary=3, the coming stack is 8-byte aligned.
push2/pop2
shouldn't be generated in this case.
