https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116588
Bug ID: 116588
Summary: wrong code with -O2 -fno-vect-cost-model
-fno-tree-dominator-opts -fno-tree-fre
--param=vrp-block-limit=0
Product: gcc
Version: 15.0
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
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Target: x86_64-pc-linux-gnu
Created attachment 59046
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=59046&action=edit
reduced testcase
Output:
$ x86_64-pc-linux-gnu-gcc -O2 -fno-vect-cost-model -fno-tree-dominator-opts
-fno-tree-fre --param=vrp-block-limit=0 testcase.c -DDEBUG
$ ./a.out
00000000a07f00008710400000000000
$ ./a.out
000000000f7f00008710400000000000
$ ./a.out
b08159c7a27f00008710400000000000
$ ./a.out
b0a1cc0ded7f00008710400000000000
$ valgrind -q --track-origins=yes ./a.out
==22934== Use of uninitialised value of size 8
==22934== at 0x48FCC79: _itoa_word (in /lib64/libc.so.6)
==22934== by 0x4906858: __printf_buffer (in /lib64/libc.so.6)
==22934== by 0x4908880: __vfprintf_internal (in /lib64/libc.so.6)
==22934== by 0x48FDC95: printf (in /lib64/libc.so.6)
==22934== by 0x4010B2: main (testcase.c:19)
==22934== Uninitialised value was created by a stack allocation
==22934== at 0x4011C0: foo (testcase.c:6)
...
The output is different on each invocation.
$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-r15-3427-20240903182055-gf0ab3de6ec0-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/15.0.0/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 --enable-libsanitizer
--disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-r15-3427-20240903182055-gf0ab3de6ec0-checking-yes-rtl-df-extra-nobootstrap-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 15.0.0 20240903 (experimental) (GCC)
