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* [Bug rtl-optimization/114243] New: -fsplit-wide-types bloats code by more than 50%
@ 2024-03-05 15:56 gjl at gcc dot gnu.org
2024-03-05 20:31 ` [Bug rtl-optimization/114243] [avr] " gjl at gcc dot gnu.org
2024-03-05 20:40 ` pinskia at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: gjl at gcc dot gnu.org @ 2024-03-05 15:56 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114243
Bug ID: 114243
Summary: -fsplit-wide-types bloats code by more than 50%
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: gjl at gcc dot gnu.org
Target Milestone: ---
Created attachment 57616
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57616&action=edit
pi-sigma.c: C99 test case
Compile the attached test case with:
$ avr-gcc pi-sigma.c -c -Os -mmcu=atmega8 -fstack-usage && avr-size pi-sigma.o
Then the code sizes are for respective versions of the compiler:
avr-gcc-v8: 624
avr-gcc-v14: 1008
which is an increase of code size of more than 60% !
The stack usage also increases by a lot. According to pi-sigma.su:
avr-gcc-v8:
-----------
pi-sigma.c:80:7:sigma 30 static
pi-sigma.c:86:7:pi_n 14 static
avr-gcc-v14:
------------
pi-sigma.c:80:7:sigma 86 static
pi-sigma.c:86:7:pi_n 36 static
That is for the 1st function the stack use almost triples!
With -fno-split-wide-types the performace of v14 code is similar to v8.
Target: avr
Configured with: ../../source/gcc-master/configure --target=avr --disable-nls
--with-dwarf2 --with-gnu-as --with-gnu-ld --disable-shared
--enable-languages=c,c++
Thread model: single
Supported LTO compression algorithms: zlib
gcc version 14.0.1 20240303 (experimental) (GCC)
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug rtl-optimization/114243] [avr] -fsplit-wide-types bloats code by more than 50%
2024-03-05 15:56 [Bug rtl-optimization/114243] New: -fsplit-wide-types bloats code by more than 50% gjl at gcc dot gnu.org
@ 2024-03-05 20:31 ` gjl at gcc dot gnu.org
2024-03-05 20:40 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: gjl at gcc dot gnu.org @ 2024-03-05 20:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114243
--- Comment #1 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
May be related to PR110093. As Vladimir noted in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110093#c5
the problem is that data flow analysis cannot cope with the subregs generated
from lower-subregs, and register alloc chokes at it.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug rtl-optimization/114243] [avr] -fsplit-wide-types bloats code by more than 50%
2024-03-05 15:56 [Bug rtl-optimization/114243] New: -fsplit-wide-types bloats code by more than 50% gjl at gcc dot gnu.org
2024-03-05 20:31 ` [Bug rtl-optimization/114243] [avr] " gjl at gcc dot gnu.org
@ 2024-03-05 20:40 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-03-05 20:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114243
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Subreg improvements to ra is planned for gcc 15 as the riscv folks are running
into it for vector modes in some cases. Maybe that will improves the situation
here.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2024-03-05 20:40 UTC | newest]
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2024-03-05 15:56 [Bug rtl-optimization/114243] New: -fsplit-wide-types bloats code by more than 50% gjl at gcc dot gnu.org
2024-03-05 20:31 ` [Bug rtl-optimization/114243] [avr] " gjl at gcc dot gnu.org
2024-03-05 20:40 ` pinskia at gcc dot gnu.org
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