https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110532
Bug ID: 110532
Summary: [14 Regression] Different results between -O0 and -O1
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: ---
Compiler Explorer: https://godbolt.org/z/xE1K6zKbs
The following code snippet:
#include <stdio.h>
unsigned char res, a[25], b[25];
#define max(a, b) ((a) > (b) ? (a) : (b))
#define min(a, b) ((a) < (b) ? (a) : (b))
int main() {
for (int i = 0; i < 25; ++i)
a[i] = 116, b[i] = 213;
res = (unsigned char)min(b[0] ? (_Bool)-11818 : a[2], max(b[2], 1));
printf("%d\n", res);
}
> $ /usr/gcc-trunk/bin/gcc -O0 bug.c; ./a.out
> 1
> $ /usr/gcc-trunk/bin/gcc -O1 bug.c; ./a.out
> 213
> $ /usr/gcc-trunk/bin/gcc -O2 bug.c; ./a.out
> 1
> $ /usr/gcc-trunk/bin/gcc -O3 bug.c; ./a.out
> 1
> $ /usr/gcc-trunk/bin/gcc -Os bug.c; ./a.out
> 1
When compiled with -O1, it prints the wrong result 213 instead of 1. 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 20230703 (experimental) [master r14-2244-g1ebf37ece3] (GCC)
