http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49781
Summary: Unnecessary lea in x32 mode
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: hjl.to...@gmail.com
[hjl@gnu-6 pr47383]$ cat x.i
static int heap[2*(256 +1+29)+1];
static int heap_len;
static int heap_max;
void
__attribute__ ((noinline))
foo (int elems)
{
int n, m;
int max_code = -1;
int node = elems;
heap_len = 0, heap_max = (2*(256 +1+29)+1);
for (n = 0; n < elems; n++)
heap[++heap_len] = max_code = n;
do {
n = heap[1];
heap[1] = heap[heap_len--];
m = heap[1];
heap[--heap_max] = n;
heap[--heap_max] = m;
} while (heap_len >= 2);
}
int
main ()
{
foo (286);
return 0;
}
[hjl@gnu-6 pr47383]$ make x.s
/export/build/gnu/gcc-x32/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc-x32/build-x86_64-linux/gcc/ -S -o x.s -mx32 -O2 -fPIC
x.i
[hjl@gnu-6 pr47383]$ cat x.s
.file "x.i"
.text
.p2align 4,,15
.globl foo
.type foo, @function
foo:
.LFB0:
.cfi_startproc
xorl %eax, %eax
testl %edi, %edi
pushq %rbx
.cfi_def_cfa_offset 16
.cfi_offset 3, -16
leal 4+heap(%rip), %ecx
jle .L10
.p2align 4,,10
.p2align 3
.L7:
leal (%rcx,%rax,4), %edx
movl %eax, (%rdx)
addl $1, %eax
cmpl %edi, %eax
jne .L7
leal -1(%rdi), %ecx
.L3:
leal -1(%rdi), %eax
movl $573, %esi
leal 2296+heap(%rip), %r11d
leal 2292+heap(%rip), %r10d
leal heap(%rip), %ebx
jmp .L5
.p2align 4,,10
.p2align 3
.L11:
leal (%rbx,%rax,4), %edx
subl $1, %eax
movl (%rdx), %ecx
.L5:
movl %eax, %edx
movl 4+heap(%rip), %r9d
subl $2, %esi
subl %edi, %edx
movl %ecx, 4+heap(%rip)
sall $3, %edx
leal (%r11,%rdx), %r8d
addl %r10d, %edx
cmpl $1, %eax
movl %r9d, (%r8)
movl %ecx, (%rdx)
jg .L11
movl %eax, heap_len(%rip)
movl %esi, heap_max(%rip)
popq %rbx
.cfi_remember_state
.cfi_def_cfa_offset 8
ret
.L10:
.cfi_restore_state
movl heap(%rip), %ecx
xorl %edi, %edi
jmp .L3
.cfi_endproc
.LFE0:
.size foo, .-foo
.section .text.startup,"ax",@progbits
.p2align 4,,15
.globl main
.type main, @function
main:
.LFB1:
.cfi_startproc
subq $8, %rsp
.cfi_def_cfa_offset 16
movl $286, %edi
call foo@PLT
xorl %eax, %eax
addq $8, %rsp
.cfi_def_cfa_offset 8
ret
.cfi_endproc
.LFE1:
.size main, .-main
.local heap_len
.comm heap_len,4,4
.local heap_max
.comm heap_max,4,4
.local heap
.comm heap,2292,32
.ident "GCC: (GNU) 4.7.0 20110718 (experimental)"
.section .note.GNU-stack,"",@progbits
[hjl@gnu-6 pr47383]$
Many lea insns can be combined with the load/store insn followed.
