https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115354
Bug ID: 115354
Summary: Large -Os code size increase related to -ftree-sra
Product: gcc
Version: 14.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: gus at projectgus dot com
Target Milestone: ---
Created attachment 58353
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58353&action=edit
Source file shows code size increase in mp_parse function
After upgrading arm-none-eabi-gcc from 13.2 to 14.1 we noticed some increases
in code size when compiling the MicroPython project with -Os.
Bisecting turned up a commit that introduces a 15% code size increase in an
(admittedly quite complex) function.
The commit is aae723d3 "sra: SRA of non-escaped aggregates passed by reference
to calls".
GCC 13.2 and the parent of commit aae723d3 both produce a 2846 byte text
section when building the attached code.
GCC 14.1, commit aae723d3, and recent master branch all produce a 3282 byte
text section.
Full compiler command line is "arm-none-eabi-gcc -Wall -Wextra -std=c99
-mcpu=cortex-m4 -Os -c"
If -fno-tree-sra argument is added then the text section reverts to 2846 bytes.
Assembler output from commit aae723d3 passing -fno-tree-sra is identical to
output from the parent commit without -fno-tree-sra.
Unfortunately the function is quite complex and includes gotos and calls to
noreturn functions. I haven't been able to isolate a smaller test case but I
thought it was worth reporting anyway, as the size jump is quite noticeable.
Version and configuration details for the local test builds:
> Target: arm-none-eabi
> Configured with: /home/gus/dev/gcc/configure --target=arm-none-eabi
> --prefix=/home/gus/ry/george/tmp/gcc-temp-aae723d3
> --with-sysroot=/home/gus/ry/george/tmp/gcc-temp-aae723d3/arm-none-eabi
> --enable-languages=c --enable-plugins --disable-decimal-float
> --disable-libffi --disable-libgomp --disable-libmudflap --disable-libquadmath
> --disable-libssp --disable-libstdcxx-pch --disable-nls --disable-shared
> --disable-threads --disable-tls --with-gnu-as --with-gnu-ld
> --with-system-zlib --with-newlib
> --with-headers=/home/gus/ry/george/tmp/gcc-temp-aae723d3/arm-none-eabi/include
> --with-python-dir=share/gcc-arm-none-eabi --with-gmp --with-mpfr --with-mpc
> --with-isl --with-libelf --enable-gnu-indirect-function
> --with-host-libstdcxx='-static-libgcc -Wl,-Bstatic,-lstdc++,-Bdynamic -lm'
> --with-multilib-list=rmprofile
> gcc version 14.0.0 20231124 (experimental) (GCC)
