https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113574
Bug ID: 113574
Summary: wrong code with shift and _BitInt(1) at any opt level
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zsojka at seznam dot cz
CC: jakub at gcc dot gnu.org
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Target: x86_64-pc-linux-gnu
Created attachment 57200
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57200&action=edit
reduced testcase
Compiler output:
$ x86_64-pc-linux-gnu-gcc testcase.c && ./a.out
Aborted
-fsanitize=undefined fixes the problem:
$ x86_64-pc-linux-gnu-gcc testcase.c -fsanitize=undefined && ./a.out
(no output)
At the ASM level, at -O1:
...
foo:
# testcase.c:7: ub1 += (ub16 << 2) | ub8;
or dil, BYTE PTR ub8[rip] # _1, ub8
and edi, 1 # _4,
it seems the shift is removed; changing the type of ub1 to "unsigned
_BitInt(2)" fixes this.
$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64//bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-r14-8373-20240123195900-gdbc5f1f523b-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/14.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--disable-bootstrap --with-cloog --with-ppl --with-isl
--build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu
--target=x86_64-pc-linux-gnu --with-ld=/usr/bin/x86_64-pc-linux-gnu-ld
--with-as=/usr/bin/x86_64-pc-linux-gnu-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-r14-8373-20240123195900-gdbc5f1f523b-checking-yes-rtl-df-extra-nobootstrap-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.0.1 20240123 (experimental) (GCC)
