https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63527
Bug ID: 63527
Summary: [5 Regression] -fPIC generates more instructions
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: hjl.tools at gmail dot com
CC: evstupac at gmail dot com
Target: i686-linux
On Linux/x86, r216154 generates more instructions with -O2 -fPIC
for
----
struct cache_file
{
char magic[sizeof "ld.so-1.7.0" - 1];
unsigned int nlibs;
};
typedef unsigned int size_t;
size_t cachesize __attribute__ ((visibility ("hidden")));
struct cache_file *cache __attribute__ ((visibility ("hidden")));
extern int __munmap (void *__addr, size_t __len);
void
_dl_unload_cache (void)
{
if (cache != ((void *)0) && cache != (struct cache_file *) -1)
{
__munmap (cache, cachesize);
cache = ((void *)0) ;
}
}
----
r216153 generates
---
.text
.LHOTB0:
.p2align 4,,15
.globl _dl_unload_cache
.type _dl_unload_cache, @function
_dl_unload_cache:
pushl %ebx
call __x86.get_pc_thunk.bx
addl $_GLOBAL_OFFSET_TABLE_, %ebx
subl $8, %esp
movl cache@GOTOFF(%ebx), %eax
leal -1(%eax), %edx
cmpl $-3, %edx
ja .L1
subl $8, %esp
pushl cachesize@GOTOFF(%ebx)
pushl %eax
call __munmap@PLT
movl $0, cache@GOTOFF(%ebx)
addl $16, %esp
.L1:
addl $8, %esp
popl %ebx
ret
.size _dl_unload_cache, .-_dl_unload_cache
.section .text.unlikely
.LCOLDE0:
.text
.LHOTE0:
.hidden cache
.comm cache,4,4
.hidden cachesize
.comm cachesize,4,4
.section
.text.__x86.get_pc_thunk.bx,"axG",@progbits,__x86.get_pc_thunk.bx,comdat
.globl __x86.get_pc_thunk.bx
.hidden __x86.get_pc_thunk.bx
.type __x86.get_pc_thunk.bx, @function
__x86.get_pc_thunk.bx:
movl (%esp), %ebx
ret
---
r216154 generates
--
.text
.LHOTB0:
.p2align 4,,15
.globl _dl_unload_cache
.type _dl_unload_cache, @function
_dl_unload_cache:
pushl %esi
pushl %ebx
call __x86.get_pc_thunk.si
addl $_GLOBAL_OFFSET_TABLE_, %esi
subl $4, %esp
movl cache@GOTOFF(%esi), %eax
leal -1(%eax), %edx
cmpl $-3, %edx
ja .L1
subl $8, %esp
pushl cachesize@GOTOFF(%esi)
movl %esi, %ebx
pushl %eax
call __munmap@PLT
movl $0, cache@GOTOFF(%esi)
addl $16, %esp
.L1:
addl $4, %esp
popl %ebx
popl %esi
ret
.size _dl_unload_cache, .-_dl_unload_cache
.section .text.unlikely
.LCOLDE0:
.text
.LHOTE0:
.hidden cache
.comm cache,4,4
.hidden cachesize
.comm cachesize,4,4
.section
.text.__x86.get_pc_thunk.si,"axG",@progbits,__x86.get_pc_thunk.si,comdat
.globl __x86.get_pc_thunk.si
.hidden __x86.get_pc_thunk.si
.type __x86.get_pc_thunk.si, @function
__x86.get_pc_thunk.si:
movl (%esp), %esi
ret
--
Why doesn't r216154 simply use %ebx to access cache, cachesize
and __munmap?
