https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110494
Bug ID: 110494 Summary: [14 Regression] Wrong code at -O3 on x86_64-pc-linux-gnu Product: gcc Version: 14.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: jwzeng at nuaa dot edu.cn Target Milestone: --- Link to the Compiler Explorer: https://godbolt.org/z/dq38c9zea The following code snippet: #include <stdio.h> unsigned long long int seed = 0; unsigned int var_1 = 631366671U; #define min(a, b) ((a) < (b) ? (a) : (b)) int main() { short a[18]; int b = 1; unsigned long long int c[18]; unsigned long long int d[18]; for (int i = 0; i < 18; ++i) a[i] = 4, c[i] = 3, d[i] = 2; for (unsigned short i = 1; i < 16; i += var_1 - 57737) a[i] = (short)min(b % (~var_1), c[i] ? d[i] : (long long unsigned int)b); for (int i = 0; i < 18; ++i) seed ^= a[i]; printf("%llu\n", seed); } > $ /usr/gcc-trunk/bin/gcc -O0 bug.c; ./a.out > 5 > $ /usr/gcc-trunk/bin/gcc -O1 bug.c; ./a.out > 5 > $ /usr/gcc-trunk/bin/gcc -O2 bug.c; ./a.out > 5 > $ /usr/gcc-trunk/bin/gcc -O3 bug.c; ./a.out > 7 > $ /usr/gcc-trunk/bin/gcc -Os bug.c; ./a.out > 5 When compiled with -O3, it prints the wrong result 7 instead of 5. Earlier GCCs do not have this bug. > $ /usr/gcc-trunk/bin/gcc --version Using built-in specs. COLLECT_GCC=/home/compilers/gcc/gcc-trunk/bin/gcc COLLECT_LTO_WRAPPER=/home/compilers/gcc/gcc-trunk/bin/../libexec/gcc/x86_64-pc-linux-gnu/14.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: ../gcc-trunk-source/gcc/configure --enable-languages=c,c++,fortran --enable-checking=release --enable-valgrind-annotations --disable-werror --disable-libstdcxx-pch --enable-libgomp --enable-lto --enable-gold --with-plugin-ld=gold --prefix=/usr/local/gcc-trunk Thread model: posix Supported LTO compression algorithms: zlib gcc version 14.0.0 20230619 (experimental) [master r14-1917-gf8e0270272] (GCC)