Closed
Description
| Bugzilla Link | 26477 |
| Version | trunk |
| OS | Linux |
| CC | @hfinkel |
Extended Description
Incoming stack of x86 interrupt handler is aligned at 4 bytes (8 bytes for
64-bit). When it calls extern functions, it needs to realign the stack
to 16-byte aligned if it is required:
[hjl@gnu-6 interrupt-1]$ cat xx.i
extern void bar (void);
extern int i;
void
__attribute__ ((interrupt))
foo (void *frame)
{
bar ();
i = 0;
}
[hjl@gnu-6 interrupt-1]$ /export/build/gnu/gcc-5/build-x86_64-linux/gcc/xgcc -B/export/build/gnu/gcc-5/build-x86_64-linux/gcc/ -O2 xx.i -m32 -mno-sse -S
[hjl@gnu-6 interrupt-1]$ cat xx.s
.file "xx.i"
.section .text.unlikely,"ax",@progbits
.LCOLDB0:
.text
.LHOTB0:
.p2align 4,,15
.globl foo
.type foo, @function
foo:
.LFB0:
.cfi_startproc
pushl %ebp
.cfi_def_cfa_offset 8
.cfi_offset 5, -8
movl %esp, %ebp
.cfi_def_cfa_register 5
pushl %ecx
pushl %edx
pushl %eax
andl $-16, %esp <<<<<<<<<<<< Align stack
cld
.cfi_offset 1, -12
.cfi_offset 2, -16
.cfi_offset 0, -20
call bar
movl $0, i
leal -12(%ebp), %esp
popl %eax
.cfi_restore 0
popl %edx
.cfi_restore 2
popl %ecx
.cfi_restore 1
popl %ebp
.cfi_restore 5
.cfi_def_cfa 4, 4
iret
.cfi_endproc
.LFE0:
.size foo, .-foo
.section .text.unlikely
.LCOLDE0:
.text
.LHOTE0:
.ident "GCC: (GNU) 5.3.1 20160201"
.section .note.GNU-stack,"",@progbits
[hjl@gnu-6 interrupt-1]$
But clang doesn't align stack:
[hjl@gnu-6 interrupt-1]$ /net/gnu-mic-2//export/build/gnu/llvm-clang/build-x86_64-linux/bin/clang -O2 xx.i -m32 -mno-sse -S
[hjl@gnu-6 interrupt-1]$ cat xx.s
.text
.file "xx.i"
.globl foo
.p2align 4, 0x90
.type foo,@function
foo: # @foo
# BB#0:
pushl %esp
pushl %edx
pushl %ecx
pushl %eax
subl $12, %esp
calll bar
movl $0, i
addl $12, %esp
popl %eax
popl %ecx
popl %edx
popl %esp
iretl
.Lfunc_end0:
.size foo, .Lfunc_end0-foo
.ident "clang version 3.9.0 (http://llvm.org/git/clang.git bf1d31e84aa2722174da56b8aff311ae04f4d9e1) (http://llvm.org/git/llvm.git 6cced9c3cd18f529420a03b100970d97512bb9a4)"
.section ".note.GNU-stack","",@progbits
[hjl@gnu-6 interrupt-1]$