https://bugs.llvm.org/show_bug.cgi?id=47523
Bug ID: 47523
Summary: [LoopInterchange] Interchange breaks program
correctness
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: chenmindong...@gmail.com
CC: llvm-bugs@lists.llvm.org
Created attachment 23956
--> https://bugs.llvm.org/attachment.cgi?id=23956&action=edit
reproducer
$ clang -mllvm -enable-loopinterchange -O2 reproducer.c -w && ./a.out
11
$ clang -O0 reproducer.c -w && ./a.out
9
LoopInterchange wrongly interchanges loops in the following function "h()", in
which the order of *s=3 matters:
struct a {
unsigned char b
} c[];
d, e, g;
f[4][9] = {5, 3};
h() {
for (; d <= 2; d++) {
for (e = 0; e <= 2; e++) {
short *s = &g;
if ((long)(f[e][d] && (*s = 3), c) % 4073709551606)
++*s;
}
}
}
main() {
h();
printf("%d\n", g);
}
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