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* [Bug tree-optimization/110494] New: [14 Regression] Wrong code at -O3 on x86_64-pc-linux-gnu
@ 2023-06-30 5:12 jwzeng at nuaa dot edu.cn
2023-06-30 5:18 ` [Bug tree-optimization/110494] " pinskia at gcc dot gnu.org
0 siblings, 1 reply; 2+ messages in thread
From: jwzeng at nuaa dot edu.cn @ 2023-06-30 5:12 UTC (permalink / raw)
To: gcc-bugs
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)
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2023-06-30 5:12 [Bug tree-optimization/110494] New: [14 Regression] Wrong code at -O3 on x86_64-pc-linux-gnu jwzeng at nuaa dot edu.cn
2023-06-30 5:18 ` [Bug tree-optimization/110494] " pinskia at gcc dot gnu.org
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