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* [Bug inline-asm/15228] New: useless copies of floating point operands
@ 2004-04-30 15:56 sylvain dot pion at sophia dot inria dot fr
2004-04-30 15:57 ` [Bug inline-asm/15228] " sylvain dot pion at sophia dot inria dot fr
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: sylvain dot pion at sophia dot inria dot fr @ 2004-04-30 15:56 UTC (permalink / raw)
To: gcc-bugs
Consider the following function :
// Forces a double to memory
double force2memdouble(double x) {
asm("" : "=m"(x) : "m"(x));
return x;
}
This is used to force a double value in memory for platforms like x86
where the FP registers have too much precision.
It gets compiled by GCC (3.4 and 3.3.3, with -O2 -fomit-frame-pointer) to :
force2memdouble:
subl $12, %esp
fldl 16(%esp)
fstpl (%esp)
fldl (%esp)
addl $12, %esp
ret
I believe that the store/load is useless, and that the function could be
compiled as simply :
force2memdouble:
fldl 4(%esp)
ret
It is interesting to note that when using "int", "float" or "long double"
instead of "double", then there is no such useless store/load.
So, is this something that could be improved in GCC ?
Maybe the code responsible for asm() adds too many requirements
on the operands for doubles ?
--
Summary: useless copies of floating point operands
Product: gcc
Version: 3.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: inline-asm
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: sylvain dot pion at sophia dot inria dot fr
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15228
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug inline-asm/15228] useless copies of floating point operands
2004-04-30 15:56 [Bug inline-asm/15228] New: useless copies of floating point operands sylvain dot pion at sophia dot inria dot fr
@ 2004-04-30 15:57 ` sylvain dot pion at sophia dot inria dot fr
2004-04-30 16:15 ` [Bug inline-asm/15228] [3.3/3.4/3.5 Regression] " pinskia at gcc dot gnu dot org
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: sylvain dot pion at sophia dot inria dot fr @ 2004-04-30 15:57 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From sylvain dot pion at sophia dot inria dot fr 2004-04-30 15:51 -------
I still have gcc 2.95 around, so I have tested with it as well.
It produces the better code that I expected :
force2memdouble:
#APP
#NO_APP
fldl 4(%esp)
ret
So, if the code is correct, then this problem is a regression on code quality
compared to 2.95.
I want to mention that this asm() is critical when implementing interval
arithmetic. Also, GMP uses that kind of asm() in mpz_get_d_2exp.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15228
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug inline-asm/15228] [3.3/3.4/3.5 Regression] useless copies of floating point operands
2004-04-30 15:56 [Bug inline-asm/15228] New: useless copies of floating point operands sylvain dot pion at sophia dot inria dot fr
2004-04-30 15:57 ` [Bug inline-asm/15228] " sylvain dot pion at sophia dot inria dot fr
@ 2004-04-30 16:15 ` pinskia at gcc dot gnu dot org
2004-05-17 11:22 ` [Bug inline-asm/15228] [3.4/3.5 " gdr at gcc dot gnu dot org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2004-04-30 16:15 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-04-30 15:57 -------
Note before 3.3 and after 2.95.3, the following sequence was used to copy the FP:
subl $12, %esp
movl 16(%esp), %edx
movl 20(%esp), %ecx
movl %edx, (%esp)
movl %ecx, 4(%esp)
Confirmed as a regression.
--
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed| |1
Keywords| |pessimizes-code
Known to fail| |3.0.4 3.2.3 3.3.3 3.4.0
| |3.5.0
Known to work| |2.95.3
Last reconfirmed|0000-00-00 00:00:00 |2004-04-30 15:57:08
date| |
Summary|useless copies of floating |[3.3/3.4/3.5 Regression]
|point operands |useless copies of floating
| |point operands
Target Milestone|--- |3.3.4
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15228
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug inline-asm/15228] [3.4/3.5 Regression] useless copies of floating point operands
2004-04-30 15:56 [Bug inline-asm/15228] New: useless copies of floating point operands sylvain dot pion at sophia dot inria dot fr
2004-04-30 15:57 ` [Bug inline-asm/15228] " sylvain dot pion at sophia dot inria dot fr
2004-04-30 16:15 ` [Bug inline-asm/15228] [3.3/3.4/3.5 Regression] " pinskia at gcc dot gnu dot org
@ 2004-05-17 11:22 ` gdr at gcc dot gnu dot org
2004-06-07 19:27 ` rth at gcc dot gnu dot org
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: gdr at gcc dot gnu dot org @ 2004-05-17 11:22 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From gdr at gcc dot gnu dot org 2004-05-16 22:11 -------
Will not fix in 3.3.x.
-- Gaby
--
What |Removed |Added
----------------------------------------------------------------------------
Summary|[3.3/3.4/3.5 Regression] |[3.4/3.5 Regression] useless
|useless copies of floating |copies of floating point
|point operands |operands
Target Milestone|3.3.4 |3.4.1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15228
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug inline-asm/15228] [3.4/3.5 Regression] useless copies of floating point operands
2004-04-30 15:56 [Bug inline-asm/15228] New: useless copies of floating point operands sylvain dot pion at sophia dot inria dot fr
` (2 preceding siblings ...)
2004-05-17 11:22 ` [Bug inline-asm/15228] [3.4/3.5 " gdr at gcc dot gnu dot org
@ 2004-06-07 19:27 ` rth at gcc dot gnu dot org
2004-06-08 16:45 ` [Bug middle-end/15228] " cvs-commit at gcc dot gnu dot org
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: rth at gcc dot gnu dot org @ 2004-06-07 19:27 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From rth at gcc dot gnu dot org 2004-06-07 19:27 -------
Testing a patch.
--
What |Removed |Added
----------------------------------------------------------------------------
CC|rth at redhat dot com |
AssignedTo|unassigned at gcc dot gnu |rth at gcc dot gnu dot org
|dot org |
Status|NEW |ASSIGNED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15228
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/15228] [3.4/3.5 Regression] useless copies of floating point operands
2004-04-30 15:56 [Bug inline-asm/15228] New: useless copies of floating point operands sylvain dot pion at sophia dot inria dot fr
` (3 preceding siblings ...)
2004-06-07 19:27 ` rth at gcc dot gnu dot org
@ 2004-06-08 16:45 ` cvs-commit at gcc dot gnu dot org
2004-06-09 23:52 ` rth at gcc dot gnu dot org
2004-06-09 23:52 ` cvs-commit at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: cvs-commit at gcc dot gnu dot org @ 2004-06-08 16:45 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From cvs-commit at gcc dot gnu dot org 2004-06-08 16:45 -------
Subject: Bug 15228
CVSROOT: /cvs/gcc
Module name: gcc
Branch: gcc-3_4-branch
Changes by: rth@gcc.gnu.org 2004-06-08 16:44:56
Modified files:
gcc : ChangeLog function.c
Log message:
PR middle-end/15228
* function.c (assign_parms): Always set_mem_align with the computed
FUNCTION_ARG_BOUNDARY. Don't clear stack_parm if !STRICT_ALIGNMENT.
Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=2.2326.2.481&r2=2.2326.2.482
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/function.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.483.4.13&r2=1.483.4.14
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15228
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/15228] [3.4/3.5 Regression] useless copies of floating point operands
2004-04-30 15:56 [Bug inline-asm/15228] New: useless copies of floating point operands sylvain dot pion at sophia dot inria dot fr
` (5 preceding siblings ...)
2004-06-09 23:52 ` rth at gcc dot gnu dot org
@ 2004-06-09 23:52 ` cvs-commit at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: cvs-commit at gcc dot gnu dot org @ 2004-06-09 23:52 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From cvs-commit at gcc dot gnu dot org 2004-06-09 23:52 -------
Subject: Bug 15228
CVSROOT: /cvs/gcc
Module name: gcc
Changes by: rth@gcc.gnu.org 2004-06-09 23:52:15
Modified files:
gcc : ChangeLog function.c
Log message:
PR middle-end/15228
* function.c (assign_parms): Always set_mem_align with the computed
FUNCTION_ARG_BOUNDARY. Don't clear stack_parm if !STRICT_ALIGNMENT.
Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.3901&r2=2.3902
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/function.c.diff?cvsroot=gcc&r1=1.520&r2=1.521
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15228
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/15228] [3.4/3.5 Regression] useless copies of floating point operands
2004-04-30 15:56 [Bug inline-asm/15228] New: useless copies of floating point operands sylvain dot pion at sophia dot inria dot fr
` (4 preceding siblings ...)
2004-06-08 16:45 ` [Bug middle-end/15228] " cvs-commit at gcc dot gnu dot org
@ 2004-06-09 23:52 ` rth at gcc dot gnu dot org
2004-06-09 23:52 ` cvs-commit at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: rth at gcc dot gnu dot org @ 2004-06-09 23:52 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From rth at gcc dot gnu dot org 2004-06-09 23:52 -------
Fixed.
--
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15228
^ permalink raw reply [flat|nested] 8+ messages in thread
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2004-04-30 15:56 [Bug inline-asm/15228] New: useless copies of floating point operands sylvain dot pion at sophia dot inria dot fr
2004-04-30 15:57 ` [Bug inline-asm/15228] " sylvain dot pion at sophia dot inria dot fr
2004-04-30 16:15 ` [Bug inline-asm/15228] [3.3/3.4/3.5 Regression] " pinskia at gcc dot gnu dot org
2004-05-17 11:22 ` [Bug inline-asm/15228] [3.4/3.5 " gdr at gcc dot gnu dot org
2004-06-07 19:27 ` rth at gcc dot gnu dot org
2004-06-08 16:45 ` [Bug middle-end/15228] " cvs-commit at gcc dot gnu dot org
2004-06-09 23:52 ` rth at gcc dot gnu dot org
2004-06-09 23:52 ` cvs-commit at gcc dot gnu dot org
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