This is the mail archive of the
gcc-bugs@gcc.gnu.org
mailing list for the GCC project.
[Bug target/40657] allocate local variables with fewer instructions
- From: "steven at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 6 Jul 2009 10:43:05 -0000
- Subject: [Bug target/40657] allocate local variables with fewer instructions
- References: <bug-40657-17659@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #4 from steven at gcc dot gnu dot org 2009-07-06 10:43 -------
Ah, heh, so you're saying that pushing/popping registers you don't have to save
may be a size optimization? That's an interesting idea.
But how to do this in GCC... The "push {lr}" is never even in the RTL. Output
with same options + "-dAP":
foo:
push {lr}
@ basic block 2
@(insn/f 20 2 21 t.c:3 (set (reg/f:SI 13 sp)
@ (plus:SI (reg/f:SI 13 sp)
@ (const_int -12 [0xfffffffffffffff4]))) 5 {*thumb1_addsi3} (nil))
@ 0x0000
sub sp, sp, #12 @ 20 *thumb1_addsi3/7 [length = 2]
@(insn 6 21 7 t.c:5 (set (reg:SI 0 r0)
@ (plus:SI (reg/f:SI 13 sp)
@ (const_int 4 [0x4]))) 5 {*thumb1_addsi3} (expr_list:REG_EQUAL
(plus:SI (reg/f:SI 13 sp)
@ (const_int 4 [0x4]))
@ (nil)))
@ 0x0002
add r0, sp, #4 @ 6 *thumb1_addsi3/6 [length = 2]
@(call_insn 7 6 13 t.c:5 (parallel [
@ (call (mem:SI (symbol_ref:SI ("bar") [flags 0x41] <function_decl
0x2000000000545200 bar>) [0 S4 A32])
@ (const_int 0 [0x0]))
@ (use (const_int 0 [0x0]))
@ (clobber (reg:SI 14 lr))
@ ]) 253 {*call_insn} (expr_list:REG_DEAD (reg:SI 0 r0)
@ (nil))
@ (expr_list:REG_DEP_TRUE (use (reg:SI 0 r0))
@ (nil)))
@ 0x0004
bl bar @ 7 *call_insn [length = 4]
@(insn 13 7 22 t.c:7 (set (reg/i:SI 0 r0)
@ (mem/c/i:SI (plus:SI (reg/f:SI 13 sp)
@ (const_int 4 [0x4])) [2 x+0 S4 A32])) 167 {*thumb1_movsi_insn}
(nil))
@ 0x0008
ldr r0, [sp, #4] @ 13 *thumb1_movsi_insn/7 [length = 2]
@(insn 23 22 16 t.c:7 (set (reg/f:SI 13 sp)
@ (plus:SI (reg/f:SI 13 sp)
@ (const_int 12 [0xc]))) 5 {*thumb1_addsi3} (nil))
@ 0x000a
add sp, sp, #12 @ 23 *thumb1_addsi3/7 [length = 2]
@(insn 24 16 25 t.c:7 (unspec:SI [
@ (reg/f:SI 13 sp)
@ ] 6) 339 {prologue_use} (nil))
@ 0x000c
@ sp needed for prologue @ 24 prologue_use [length = 0]
@(jump_insn 25 24 26 t.c:7 (unspec_volatile [
@ (return)
@ ] 1) 321 {*epilogue_insns} (nil))
@ 0x000c
pop {pc}
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40657