https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120254
Bug ID: 120254
Summary: wrong code at -O3 on x86_64-pc-linux-gnu
Product: gcc
Version: 15.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zhiyijie at zju dot edu.cn
Target Milestone: ---
Created attachment 61416
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=61416&action=edit
test case
It produces wrong code when compiling using gcc-15.1.0 with -O3 option. I get
sum of array A as -1957771396 using -O0 and -O2, but 1793347916 using -O3.
This situation disappears when I lower the number of "N"(e.g., from 30 to 10),
and also when I add "-fno-tree-vectorize".
Here is the kernel function:
#define N 30
for (int i = 0; i < N - 1; i++) {
for (int j = 0; j < N; j++) {
for (int k = 0; k < N - 1; k++) {
A[k + 1][i][i] += A[k + 1][i][i + 1] - A[k][i][i] - 6;
}
}
}
$ gcc-15 -O0 ./test.c -o ./test0
$ ./test0
-1957771396
$ gcc-15 -O3 ./test.c -o ./test3
$ ./test3
1793347916
$ gcc-15 -O3 -fno-tree-vectorize ./test.c -o ./test3_
$ ./test3_
-1957771396
$ gcc-15 -v
Using built-in specs.
Target: x86_64-pc-linux-gnu
Configured with: ../configure --enable-languages=c,c++,fortran
--disable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 15.1.0 (GCC)
