https://sourceware.org/bugzilla/show_bug.cgi?id=32516
Bug ID: 32516
Summary: [RISCV] No compressed c.j for offsets of -2044, -2046,
-2048
Product: binutils
Version: 2.44 (HEAD)
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: gas
Assignee: unassigned at sourceware dot org
Reporter: tommy_murphy at hotmail dot com
Target Milestone: ---
Created attachment 15870
--> https://sourceware.org/bugzilla/attachment.cgi?id=15870&action=edit
cj.S - test case
Originally reported here:
https://github.com/riscv-collab/riscv-gnu-toolchain/issues/1647
and then incorrectly logged by me against GCC here:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118284
See the attached simple test code cj.S - note the "Goto +..." comments for how
to adjust the offset between 2040 and 2048 in increments of 2 bytes.
For offsets of up to -2040 and also -2042 a 16-bit compressed c.j <offset> is
generated but for offsets of -2044, -2046 and -2048 a 32-bit (non-compressed)
jal x0, <offset> instruction is generated.
Is this an offset edge case error in the code generation or is there some other
explanation for this behaviour that means that this behaviour is actually
expected?
If any further information or clarification is needed please let me know.
Thanks! :-)
Tested with riscv-gnu-toolchain GCC 14.2.0 and Binutils master branch at commit
abbdd7248999ad66c0b59aa9656866ee1931b913.
git clone https://github.com/riscv-collab/riscv-gnu-toolchain
cd riscv-gnu-toolchain
git clone https://github.com/bminor/binutils-gdb binutils-upstream-master
--depth=1
./configure --prefix=`pwd`/installed-tools --disable-gdb
--with-binutils-src=`pwd`/binutils-upstream-master
make
./riscv64-unknown-elf-gcc -v
Using built-in specs.
COLLECT_GCC=./riscv64-unknown-elf-gcc
COLLECT_LTO_WRAPPER=/home/user/issue-1647/installed-tools/libexec/gcc/riscv64-unknown-elf/14.2.0/lto-wrapper
Target: riscv64-unknown-elf
Configured with: /home/user/issue-1647/gcc/configure
--target=riscv64-unknown-elf --prefix=/home/user/issue-1647/installed-tools
--disable-shared --disable-threads --enable-languages=c,c++
--with-pkgversion=g04696df09 --with-system-zlib --enable-tls --with-newlib
--with-sysroot=/home/user/issue-1647/installed-tools/riscv64-unknown-elf
--with-native-system-header-dir=/include --disable-libmudflap --disable-libssp
--disable-libquadmath --disable-libgomp --disable-nls
--disable-tm-clone-registry --src=.././gcc --disable-multilib --with-abi=lp64d
--with-arch=rv64gc --with-tune=rocket --with-isa-spec=20191213
'CFLAGS_FOR_TARGET=-Os -mcmodel=medlow' 'CXXFLAGS_FOR_TARGET=-Os
-mcmodel=medlow'
Thread model: single
Supported LTO compression algorithms: zlib
gcc version 14.2.0 (g04696df09)
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