https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120368
Bug ID: 120368
Summary: [16 Regression] wrong code with -O
-fno-forward-propagate
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zsojka at seznam dot cz
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Target: riscv64-unknown-linux-gnu
Created attachment 61479
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=61479&action=edit
reduced testcase
Output:
$ riscv64-unknown-linux-gnu-gcc -O -fno-forward-propagate testcase.c -static
$ qemu-riscv64 -- ./a.out
Aborted
The difference between gcc-15 and gcc-16 is:
--- testcase-15.s 2025-05-20 19:45:14.691632688 +0200
+++ testcase-16.s 2025-05-20 19:44:37.391837369 +0200
@@ -10,7 +10,7 @@
foo:
.LFB0:
.cfi_startproc
- sraw a1,a1,a0
+ sra a1,a1,a0
andi a1,a1,0xff
slliw a0,a1,8
addw a0,a0,a1
but I have no explanation why gcc-15 generates sraw
$ riscv64-unknown-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-riscv64/bin/riscv64-unknown-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-20250520175601-r16-761-gd44beb132850a8-checking-yes-rtl-df-extra-riscv64/bin/../libexec/gcc/riscv64-unknown-linux-gnu/16.0.0/lto-wrapper
Target: riscv64-unknown-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--with-isa-spec=2.2 --with-sysroot=/usr/riscv64-unknown-linux-gnu
--build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu
--target=riscv64-unknown-linux-gnu
--with-ld=/usr/bin/riscv64-unknown-linux-gnu-ld
--with-as=/usr/bin/riscv64-unknown-linux-gnu-as --disable-multilib
--enable-libsanitizer --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-20250520175601-r16-761-gd44beb132850a8-checking-yes-rtl-df-extra-riscv64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 16.0.0 20250520 (experimental) (GCC)
