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* [Bug target/42500] New: unnecessary register move
@ 2009-12-25 12:47 carrot at google dot com
2009-12-30 0:08 ` [Bug target/42500] " ramana at gcc dot gnu dot org
` (7 more replies)
0 siblings, 8 replies; 9+ messages in thread
From: carrot at google dot com @ 2009-12-25 12:47 UTC (permalink / raw)
To: gcc-bugs
Compile the following code with options -O2
extern "C" void foo(int a[4]);
extern "C" void bar(int a, int b, int c, int d)
{
int v[4] = {a,b,c,d};
foo(v);
foo(v);
}
GCC generates
bar:
stmfd sp!, {r4, lr}
.save {r4, lr}
.LCFI0:
.pad #16
sub sp, sp, #16
.LCFI1:
mov lr, #0
add ip, sp, #8
str lr, [ip], #4
str r0, [sp, #0]
mov r0, sp
str lr, [ip, #0]
stmib sp, {r1, r2, r3} @ phole stm
bl foo
mov r0, sp
mov r4, sp // A
bl foo
add sp, sp, #16
ldmfd sp!, {r4, lr}
bx lr
Instruction A move sp to r4, but r4 is never used again.
If compile the code with options -Os, the result is even worse:
bar:
stmfd sp!, {r0, r1, r2, r3, r4, r5, r6, r7, r8, lr}
.save {r0, r1, r2, r3, r4, r5, r6, r7, r8, lr}
.LCFI0:
mov r6, r0
mov r5, r1
mov r4, r2
mov r1, #0
mov r2, #16
mov r0, sp
mov r8, r3
bl memset
mov r0, sp
str r6, [sp, #0]
str r5, [sp, #4]
str r4, [sp, #8]
str r8, [sp, #12]
bl foo
mov r0, sp
mov r7, sp
bl foo
ldmfd sp!, {r0, r1, r2, r3, r4, r5, r6, r7, r8, lr}
bx lr
It calls memset to set the array to 0, then store parameters to that array. It
is quite inefficient.
--
Summary: unnecessary register move
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: carrot at google dot com
GCC build triplet: i686-linux
GCC host triplet: i686-linux
GCC target triplet: arm-eabi
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42500
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug target/42500] unnecessary register move
2009-12-25 12:47 [Bug target/42500] New: unnecessary register move carrot at google dot com
@ 2009-12-30 0:08 ` ramana at gcc dot gnu dot org
2009-12-30 0:10 ` ramana at gcc dot gnu dot org
` (6 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: ramana at gcc dot gnu dot org @ 2009-12-30 0:08 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from ramana at gcc dot gnu dot org 2009-12-30 00:08 -------
What architecture options are you using ? With .ident "GCC: (GNU)
4.5.0 20091229 (experimental)" and -O2 I get the redundant move into r4 of sp .
But for -Os I get the following very different code. I don't see the call to
memset ever.
.text
.align 2
.global foo
.type foo, %function
foo:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
stmfd sp!, {r0, r1, r2, lr} @,
mov r3, r0 @ a, a
ldr r2, [r0, #12] @ tmp142,
str r2, [sp, #0] @ tmp142,
ldr r0, .L2 @,
ldmia r3, {r1, r2, r3} @ phole ldm
bl printf @
ldmfd sp!, {r1, r2, r3, pc}
.L3:
.align 2
.L2:
.word .LC0
.size foo, .-foo
.section .rodata.str1.1,"aMS",%progbits,1
.LC0:
.ascii "%d %d %d %d \012\000"
.ident "GCC: (GNU) 4.5.0 20091229 (experimental)"
.section .note.GNU-stack,"",%progbits
--
ramana at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|unnecessary register move |unnecessary register move
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42500
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug target/42500] unnecessary register move
2009-12-25 12:47 [Bug target/42500] New: unnecessary register move carrot at google dot com
2009-12-30 0:08 ` [Bug target/42500] " ramana at gcc dot gnu dot org
@ 2009-12-30 0:10 ` ramana at gcc dot gnu dot org
2009-12-30 6:46 ` carrot at google dot com
` (5 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: ramana at gcc dot gnu dot org @ 2009-12-30 0:10 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from ramana at gcc dot gnu dot org 2009-12-30 00:10 -------
(In reply to comment #1)
> What architecture options are you using ? With .ident "GCC: (GNU)
> 4.5.0 20091229 (experimental)" and -O2 I get the redundant move into r4 of sp .
>
> But for -Os I get the following very different code. I don't see the call to
> memset ever. \
Sorry I meant this rather than the code in comment #1
bar:
@ args = 0, pretend = 0, frame = 16
@ frame_needed = 0, uses_anonymous_args = 0
stmfd sp!, {r0, r1, r2, r3, r4, lr}
str r0, [sp, #0]
mov r0, sp
stmib sp, {r1, r2, r3} @ phole stm
bl foo
mov r0, sp
mov r4, sp
bl foo
ldmfd sp!, {r0, r1, r2, r3, r4, pc}
.size bar, .-bar
.ident "GCC: (GNU) 4.5.0 20091229 (experimental)"
.section .note.GNU-stack,"",%progbits
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42500
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug target/42500] unnecessary register move
2009-12-25 12:47 [Bug target/42500] New: unnecessary register move carrot at google dot com
2009-12-30 0:08 ` [Bug target/42500] " ramana at gcc dot gnu dot org
2009-12-30 0:10 ` ramana at gcc dot gnu dot org
@ 2009-12-30 6:46 ` carrot at google dot com
2009-12-30 19:15 ` [Bug c++/42500] Unnecessary call to memset to initialize array at Os ramana at gcc dot gnu dot org
` (4 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: carrot at google dot com @ 2009-12-30 6:46 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from carrot at google dot com 2009-12-30 06:46 -------
My complete command line:
"/home/carrot/compiler/armobj/gcc/cc1plus" "-fpreprocessed" "testH.ii" "-quiet"
"-dumpbase" "testH.cpp" "-auxbase-strip" "obj/./testH.o" "-Os" "-o" "testH.s"
Please compile it as C++ program. When I compiled it as C program, I got the
same result as yours.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42500
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug c++/42500] Unnecessary call to memset to initialize array at Os
2009-12-25 12:47 [Bug target/42500] New: unnecessary register move carrot at google dot com
` (2 preceding siblings ...)
2009-12-30 6:46 ` carrot at google dot com
@ 2009-12-30 19:15 ` ramana at gcc dot gnu dot org
2010-03-16 15:51 ` [Bug rtl-optimization/42500] Unnecessary mov of sp to a register bernds at codesourcery dot com
` (3 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: ramana at gcc dot gnu dot org @ 2009-12-30 19:15 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from ramana at gcc dot gnu dot org 2009-12-30 19:14 -------
Ok (In reply to comment #3)
> My complete command line:
>
> "/home/carrot/compiler/armobj/gcc/cc1plus" "-fpreprocessed" "testH.ii" "-quiet"
> "-dumpbase" "testH.cpp" "-auxbase-strip" "obj/./testH.o" "-Os" "-o" "testH.s"
>
> Please compile it as C++ program. When I compiled it as C program, I got the
> same result as yours.
Ok that is a subject of a separate bug report that has been filed at PR42556.
Let this remain about just the redundant move of sp into r4.
Ramana
--
ramana at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Component|target |c++
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2009-12-30 19:14:49
date| |
Summary|unnecessary register move |Unnecessary call to memset
| |to initialize array at Os
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42500
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug rtl-optimization/42500] Unnecessary mov of sp to a register
2009-12-25 12:47 [Bug target/42500] New: unnecessary register move carrot at google dot com
` (3 preceding siblings ...)
2009-12-30 19:15 ` [Bug c++/42500] Unnecessary call to memset to initialize array at Os ramana at gcc dot gnu dot org
@ 2010-03-16 15:51 ` bernds at codesourcery dot com
2010-06-04 12:44 ` bernds at gcc dot gnu dot org
` (2 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: bernds at codesourcery dot com @ 2010-03-16 15:51 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from bernds at codesourcery dot com 2010-03-16 15:51 -------
I believe this is exactly the same problem as PR40615.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42500
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug rtl-optimization/42500] Unnecessary mov of sp to a register
2009-12-25 12:47 [Bug target/42500] New: unnecessary register move carrot at google dot com
` (4 preceding siblings ...)
2010-03-16 15:51 ` [Bug rtl-optimization/42500] Unnecessary mov of sp to a register bernds at codesourcery dot com
@ 2010-06-04 12:44 ` bernds at gcc dot gnu dot org
2010-06-07 22:46 ` bernds at gcc dot gnu dot org
2010-06-08 15:31 ` hjl dot tools at gmail dot com
7 siblings, 0 replies; 9+ messages in thread
From: bernds at gcc dot gnu dot org @ 2010-06-04 12:44 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from bernds at gcc dot gnu dot org 2010-06-04 12:44 -------
Subject: Bug 42500
Author: bernds
Date: Fri Jun 4 12:44:01 2010
New Revision: 160260
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=160260
Log:
PR rtl-optimization/39871
PR rtl-optimization/40615
PR rtl-optimization/42500
PR rtl-optimization/42502
* ira.c (init_reg_equiv_memory_loc: New function.
(ira): Call it twice.
* reload.h (calculate_elim_costs_all_insns): Declare.
* ira-costs.c: Include "reload.h".
(regno_equiv_gains): New static variable.
(init_costs): Allocate it.
(finish_costs): Free it.
(ira_costs): Call calculate_elim_costs_all_insns.
(find_costs_and_classes): Take estimated elimination costs
into account.
(ira_adjust_equiv_reg_cost): New function.
* ira.h (ira_adjust_equiv_reg_cost): Declare it.
* reload1.c (init_eliminable_invariants, free_reg_equiv,
elimination_costs_in_insn, note_reg_elim_costly): New static
functions.
(elim_bb): New static variable.
(reload): Move code out of here into init_eliminable_invariants and
free_reg_equiv. Call them.
(calculate_elim_costs_all_insns): New function.
(eliminate_regs_1): Declare. Add extra arg FOR_COSTS;
all callers changed. If FOR_COSTS is true, don't call alter_reg,
but call note_reg_elim_costly if we turned a valid memory address
into an invalid one.
* Makefile.in (ira-costs.o): Depend on reload.h.
testsuite/
PR rtl-optimization/39871
PR rtl-optimization/40615
PR rtl-optimization/42500
PR rtl-optimization/42502
* gcc.target/arm/eliminate.c: New test.
Added:
trunk/gcc/testsuite/gcc.target/arm/eliminate.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/Makefile.in
trunk/gcc/ira-costs.c
trunk/gcc/ira.c
trunk/gcc/ira.h
trunk/gcc/reload.h
trunk/gcc/reload1.c
trunk/gcc/testsuite/ChangeLog
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42500
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug rtl-optimization/42500] Unnecessary mov of sp to a register
2009-12-25 12:47 [Bug target/42500] New: unnecessary register move carrot at google dot com
` (5 preceding siblings ...)
2010-06-04 12:44 ` bernds at gcc dot gnu dot org
@ 2010-06-07 22:46 ` bernds at gcc dot gnu dot org
2010-06-08 15:31 ` hjl dot tools at gmail dot com
7 siblings, 0 replies; 9+ messages in thread
From: bernds at gcc dot gnu dot org @ 2010-06-07 22:46 UTC (permalink / raw)
To: gcc-bugs
------- Comment #7 from bernds at gcc dot gnu dot org 2010-06-07 22:46 -------
Fixed.
--
bernds at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42500
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug rtl-optimization/42500] Unnecessary mov of sp to a register
2009-12-25 12:47 [Bug target/42500] New: unnecessary register move carrot at google dot com
` (6 preceding siblings ...)
2010-06-07 22:46 ` bernds at gcc dot gnu dot org
@ 2010-06-08 15:31 ` hjl dot tools at gmail dot com
7 siblings, 0 replies; 9+ messages in thread
From: hjl dot tools at gmail dot com @ 2010-06-08 15:31 UTC (permalink / raw)
To: gcc-bugs
--
hjl dot tools at gmail dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |4.6.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42500
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2010-06-08 15:31 UTC | newest]
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2009-12-25 12:47 [Bug target/42500] New: unnecessary register move carrot at google dot com
2009-12-30 0:08 ` [Bug target/42500] " ramana at gcc dot gnu dot org
2009-12-30 0:10 ` ramana at gcc dot gnu dot org
2009-12-30 6:46 ` carrot at google dot com
2009-12-30 19:15 ` [Bug c++/42500] Unnecessary call to memset to initialize array at Os ramana at gcc dot gnu dot org
2010-03-16 15:51 ` [Bug rtl-optimization/42500] Unnecessary mov of sp to a register bernds at codesourcery dot com
2010-06-04 12:44 ` bernds at gcc dot gnu dot org
2010-06-07 22:46 ` bernds at gcc dot gnu dot org
2010-06-08 15:31 ` hjl dot tools at gmail dot com
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