[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
--- Additional Comments From cvs-commit at gcc dot gnu dot org 2005-02-09 14:43 --- Subject: Bug 19597 CVSROOT:/cvs/gcc Module name:gcc Changes by: [EMAIL PROTECTED] 2005-02-09 14:43:29 Modified files: gcc: ChangeLog gcc/config/avr : avr.c Log message: PR target/19597 * config/avr/avr.c (default_rtx_costs): Delete. (avr_operand_rtx_cost): New function. (avr_rtx_costs): Completely rewrite. Patches: http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gccr1=2.7419r2=2.7420 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/config/avr/avr.c.diff?cvsroot=gccr1=1.128r2=1.129 -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
--- Additional Comments From pinskia at gcc dot gnu dot org 2005-02-09 14:49 --- Fixed for real this time. -- What|Removed |Added Status|REOPENED|RESOLVED Resolution||FIXED Target Milestone|--- |4.0.0 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
--- Additional Comments From pinskia at gcc dot gnu dot org 2005-02-09 07:02 --- Fixed. Thanks Roger for looking into this testcase. And thanks for all people who tested the patch to show it actually helps the code size. -- What|Removed |Added Status|NEW |RESOLVED Resolution||FIXED Target Milestone|--- |4.0.0 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
--- Additional Comments From pinskia at gcc dot gnu dot org 2005-02-09 07:16 --- Actually Roger has not checked this in yet. I was misled by: http://gcc.gnu.org/ml/gcc-patches/2005-02/msg00344.html. -- What|Removed |Added Status|RESOLVED|REOPENED Resolution|FIXED | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
-- What|Removed |Added Target Milestone|4.0.0 |--- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
--- Additional Comments From schlie at comcast dot net 2005-01-25 20:33 --- (In reply to comment #9) Not good. With these two patches applied, the size of four big AVR applications increased slightly. Although it would have been nicer if all 4 got smaller, it's not clear that a 0.5% code size variance means much of anything good or bad. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
--- Additional Comments From roger at eyesopen dot com 2005-01-25 21:23 --- I'm currently working on an updated and improved patch that should address some of this size regression. Failing that there are a number of middle-end improvements that can be made to address the code size increase. For example, GCC's middle-end considers any constant with an rtx_cost greater than COSTS_N_INSNS(1) to be expensive, and therefore worth keeping in a register for CSE and GCSE. Unfortunately, this plays badly with AVR, where the cost of a register-register copy is often greater than COSTS_N_INSNS(1)! The solution to which is to introduce a REG_REG_MOVE_COST(mode) target macro that can be used to report the cost of copying a pseudo and use this instead of COSTS_N_INSNS(1) where appropriate. This should even help non-AVR platforms, for example DImode typically requires two move instructions. The change described above should avoid AVR keeping HImode integer constants in registers and then copying them when required (its as cheap to load an immediate constant as it is to copy registers, but the later increases register pressure, stack frame size, etc...) -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
--- Additional Comments From schlie at comcast dot net 2005-01-25 23:19 --- (In reply to comment #11) The change described above should avoid AVR keeping HImode integer constants in registers and then copying them when required (its as cheap to load an immediate constant as it is to copy registers, but the later increases register pressure, stack frame size, etc...) Just as a minor clarification, HI-mode register-to-register moves are relativly cheap on avr (i.e. 1-instruction/1-cycle if allocated in an register pair), so there may often be circumstances when keeping frequently-recently used HI constants in registers may actually be cheaper than loading them upon demand (as QI-mode constant loads are limited to r16-r31), and although an HI-mode constant may be arbitrarity loaded from data-memory, they would need to have been stored there first in anticipation of their requirement, unfortunatly further complecated by data-memory itself tending to be a very scarce/limited resource (nor is it clear how to best express this potential method or cost to GCC if considered worth while)? (however, more accurrately describing true inst. costs should only help improve code effeciency) -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
--- Additional Comments From pinskia at gcc dot gnu dot org 2005-01-24 08:16 --- (In reply to comment #4) But to summarise, this is a target bug. That is what I thought. Anyways Roger posted a patch to rewrite rtx_cost for AVR to fix this bug here: http://gcc.gnu.org/ml/ gcc-patches/2005-01/msg01698.html It might also improve other things too because of the mentioned items in that mail. -- What|Removed |Added Keywords||patch http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
--- Additional Comments From giovannibajo at libero dot it 2005-01-24 08:56 --- Marek, can you review this patch please? -- What|Removed |Added CC||marekm at gcc dot gnu dot ||org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
--- Additional Comments From marekm at amelek dot gda dot pl 2005-01-24 09:24 --- Subject: Re: [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code On Mon, Jan 24, 2005 at 08:56:46AM -, giovannibajo at libero dot it wrote: Marek, can you review this patch please? http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597 Thanks. Reviewing this will take some time - I agree the current rtx costs are not perfect, but changing them can affect generated code in unexpected ways. It would be good to test it a lot on various test cases, to make sure it doesn't introduce new code size regressions... Marek -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
--- Additional Comments From bernie at develer dot com 2005-01-24 10:28 --- Subject: Re: [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code marekm at amelek dot gda dot pl wrote: --- Additional Comments From marekm at amelek dot gda dot pl 2005-01-24 09:24 --- Subject: Re: [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code On Mon, Jan 24, 2005 at 08:56:46AM -, giovannibajo at libero dot it wrote: Marek, can you review this patch please? http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597 Thanks. Reviewing this will take some time - I agree the current rtx costs are not perfect, but changing them can affect generated code in unexpected ways. It would be good to test it a lot on various test cases, to make sure it doesn't introduce new code size regressions... I'm building avr-gcc right now with your two patches and this one applied. I'll let you know shortly. btw, how do you test the AVR backend? Can you execute the dejagnu testsuite on simulavr or something similar? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
[Bug target/19597] [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code
--- Additional Comments From bernie at develer dot com 2005-01-24 13:15 --- Subject: Re: [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code Bernardo Innocenti wrote: marekm at amelek dot gda dot pl wrote: --- Additional Comments From marekm at amelek dot gda dot pl 2005-01-24 09:24 --- Subject: Re: [4.0 Regression] avr-gcc 4.0, multiplication by constant, very long code On Mon, Jan 24, 2005 at 08:56:46AM -, giovannibajo at libero dot it wrote: Marek, can you review this patch please? http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597 Thanks. Reviewing this will take some time - I agree the current rtx costs are not perfect, but changing them can affect generated code in unexpected ways. It would be good to test it a lot on various test cases, to make sure it doesn't introduce new code size regressions... I'm building avr-gcc right now with your two patches and this one applied. I'll let you know shortly. Not good. With these two patches applied, the size of four big AVR applications increased slightly. These were built with -Os (the second one shows a minor improvement): textdata bss dec hex filename 8008 136 40185452161 images-orig/dspslave.elf 8032 136 40185692179 images-patched/dspslave.elf textdata bss dec hex filename 18448 536 692 196764cdc images-orig/dspmaster.elf 18428 536 692 196564cc8 images-patched/dspmaster.elf These with -O2: textdata bss dec hex filename 6045418321562 63848f968 images-orig/kfront.elf 6048818321562 63882f98a images-patched/kfront.elf textdata bss dec hex filename 36160 9001713 387739775 images-orig/kcntrl.elf 36344 9001713 38957982d images-patched/kcntrl.elf Would you like to see some diffs? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
