https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102511
Bug ID: 102511
Summary: GCC produces incorrect code for -O3: first element of
the array is skipped
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: vsevolod.livinskij at frtk dot ru
Target Milestone: ---
Reproducer:
//func.cpp
extern char arr_15[];
void test(signed char a, unsigned short b, unsigned long long c,
unsigned short f) {
for (int d = b - 8; d < b; d += 2)
for (short e = 0; e < (unsigned short)((f ? 122 : 0) ^ (a ? c : 0)) -
64055;
e += 3)
arr_15[d] = 42;
}
//driver.cpp
#include <stdio.h>
unsigned char arr_15 [8];
void test(signed char a, unsigned short b, unsigned long long int c, unsigned
short f);
int main() {
test(37, 8, 12325048486467861044ULL, 45936);
for (size_t i_0 = 0; i_0 < 8; ++i_0)
printf("%d ", arr_15 [i_0]);
printf("\n");
}
Error:
>$ g++ -O3 driver.cpp func.cpp && ./a.out
0 0 42 0 42 0 42 0
>$ g++ -O2 driver.cpp func.cpp && ./a.out
42 0 42 0 42 0 42 0
GCC version:
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/testing/gcc/bin/libexec/gcc/x86_64-pc-linux-gnu/12.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /testing/gcc/gcc_src/configure --enable-multilib
--prefix=/testing/gcc/bin --disable-bootstrap
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 12.0.0 20210927 (51018dd1395c72b3681ae5f84eceb94320472922) (GCC)
