https://bugs.llvm.org/show_bug.cgi?id=38125
Bug ID: 38125
Summary: clang miscompiles at -O2 and above on valid code
Product: clang
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: LLVM Codegen
Assignee: unassignedclangb...@nondot.org
Reporter: helloqi...@gmail.com
CC: llvm-bugs@lists.llvm.org
It seems to be a recent regression.
$ clang-trunk -v
clang version 7.0.0 (trunk 336646)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
$ clang-trunk abc.c ; ./a.out
0
FFFFFFFA
$ clang-trunk -O2 abc.c ; ./a.out
0
5
$ cat abc.c
int printf(char *, ...);
int a, c;
unsigned short b;
short d;
void fn1(char p1) { a = a ^ p1; }
void fn2(long p1) {
a = p1 & 5;
fn1(p1 >> 56);
}
int main() {
for (; c >= 0; c--)
d = -3L;
d |= b;
fn2(d);
printf("%d\n", b);
printf("%X\n", a);
}
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