------- Comment #3 from steven at gcc dot gnu dot org 2009-06-20 07:23 -------
Output from ./cc1 -march=armv5te -mthumb -Os PR40499.c -dAP:
.file "PR40499.c"
.text
.align 1
.global dual_feasible
.code 16
.thumb_func
.type dual_feasible, %function
dual_feasible:
@ basic block 2
@(insn 42 37 43 PR40499.c:11 (set (reg/v/f:SI 2 r2 [orig:169 stop ] [169])
@ (mem/s/f:SI (plus:SI (reg/v/f:SI 0 r0 [orig:172 net ] [172])
@ (const_int 4 [0x4])) [3 <variable>.stop_arcs+0 S4 A32])) 168
{*thumb1_movsi_insn} (nil))
@ 0x0000
ldr r2, [r0, #4] @ 42 *thumb1_movsi_insn/7 [length = 2]
@(insn 43 42 108 PR40499.c:13 (set (reg/v/f:SI 3 r3 [orig:167 arc ] [167])
@ (mem/s/f:SI (reg/v/f:SI 0 r0 [orig:172 net ] [172]) [3
<variable>.arcs+0 S4 A32])) 168 {*thumb1_movsi_insn} (expr_list:REG_DEAD
(reg/v/f:SI 0 r0 [orig:172 net ] [172])
@ (nil)))
@ 0x0002
ldr r3, [r0] @ 43 *thumb1_movsi_insn/7 [length = 2]
@(jump_insn 108 43 109 PR40499.c:13 (set (pc)
@ (label_ref 51)) 243 {*thumb_jump} (nil))
@ 0x0004
b .L2 @ 108 *thumb_jump [length = 2]
.L4:
@ basic block 3
@(insn 47 46 48 PR40499.c:15 (set (reg:SI 1 r1 [173])
@ (mem:SI (reg/v/f:SI 3 r3 [orig:167 arc ] [167]) [4 S4 A32])) 168
{*thumb1_movsi_insn} (expr_list:REG_EQUIV (mem:SI (reg/v/f:SI 3 r3 [orig:167
arc ] [167]) [4 S4 A32])
@ (nil)))
@ 0x0006
ldr r1, [r3] @ 47 *thumb1_movsi_insn/7 [length = 2]
@(jump_insn 48 47 49 PR40499.c:15 (set (pc)
@ (if_then_else (le (reg:SI 1 r1 [173])
@ (const_int 7 [0x7]))
@ (label_ref:SI 70)
@ (pc))) 200 {*cbranchsi4_insn} (expr_list:REG_DEAD (reg:SI 1 r1
[173])
@ (expr_list:REG_BR_PROB (const_int 450 [0x1c2])
@ (nil))))
@ 0x0008
cmp r1, #7 @ 48 *cbranchsi4_insn/1 [length = 4]
ble .L5
@ basic block 4
@(insn 50 49 51 PR40499.c:13 (set (reg/v/f:SI 3 r3 [orig:167 arc ] [167])
@ (plus:SI (reg/v/f:SI 3 r3 [orig:167 arc ] [167])
@ (const_int 4 [0x4]))) 5 {*thumb1_addsi3} (nil))
@ 0x000c
add r3, r3, #4 @ 50 *thumb1_addsi3/1 [length = 2]
.L2:
@ basic block 5
@(jump_insn 54 52 66 PR40499.c:13 (set (pc)
@ (if_then_else (ltu (reg/v/f:SI 3 r3 [orig:167 arc ] [167])
@ (reg/v/f:SI 2 r2 [orig:169 stop ] [169]))
@ (label_ref 53)
@ (pc))) 200 {*cbranchsi4_insn} (expr_list:REG_BR_PROB (const_int
9550 [0x254e])
@ (nil)))
@ 0x000e
cmp r3, r2 @ 54 *cbranchsi4_insn/1 [length = 4]
bcc .L4
@ basic block 6
@(insn 38 66 110 PR40499.c:13 (set (reg:SI 0 r0 [orig:168 D.1218 ] [168])
@ (const_int 0 [0x0])) 168 {*thumb1_movsi_insn} (expr_list:REG_EQUAL
(const_int 0 [0x0])
@ (nil)))
@ 0x0012
mov r0, #0 @ 38 *thumb1_movsi_insn/2 [length = 2]
@(jump_insn 110 38 111 (set (pc)
@ (label_ref 55)) 243 {*thumb_jump} (nil))
@ 0x0014
b .L3 @ 110 *thumb_jump [length = 2]
.L5:
@ basic block 7
@(insn 39 69 55 PR40499.c:15 (set (reg:SI 0 r0 [orig:168 D.1218 ] [168])
@ (const_int 1 [0x1])) 168 {*thumb1_movsi_insn} (expr_list:REG_EQUAL
(const_int 1 [0x1])
@ (nil)))
@ 0x0016
mov r0, #1 @ 39 *thumb1_movsi_insn/2 [length = 2]
.L3:
@ basic block 8
@(insn 98 97 99 PR40499.c:22 (unspec:SI [
@ (reg/f:SI 13 sp)
@ ] 6) 341 {prologue_use} (nil))
@ 0x0018
@ sp needed for prologue @ 98 prologue_use [length = 4]
@(jump_insn 100 99 101 PR40499.c:22 (unspec_volatile [
@ (return)
@ ] 1) 323 {*epilogue_insns} (nil))
@ 0x001c
bx lr
.size dual_feasible, .-dual_feasible
.ident "GCC: (GNU) 4.5.0 20090614 (experimental) [trunk revision
148472]"
There are several interesting things going on here:
1. Note how "prologue_use" has length 4, that's probably wrong (should be
length 0?).
2. Note "epilogue_insns". For thumb this pattern outputs instructions directly
to the cc1 output (i.e. the .s file), so these insns are never seen by
thread_prologue_and_epilogue_insns. Basically the thumb1 epilogue_insns is an
old-style text epilogue_insns instead of an RTL epilogue.
--
steven at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |NEW
Ever Confirmed|0 |1
GCC host triplet|i686-linux |
Last reconfirmed|0000-00-00 00:00:00 |2009-06-20 07:23:38
date| |
Summary|[missed optimization] branch|[missed optimization] branch
|to return |to return not threaded on
| |thumb
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40499
