https://bugs.llvm.org/show_bug.cgi?id=51519
Bug ID: 51519
Summary: WRONG CODE: bad integer conversion at -O1/-Og
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: Scalar Optimizations
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
This program involves a conversion from signed to unsigned and then back again,
which should be well-defined. I understand that llvm should follow gccs
bahaviour found here:
https://gcc.gnu.org/onlinedocs/gcc/Integers-implementation.html#Integers-implementation.
It seems to print '1' typically, except at -O1 (and -Og) for some reason:
gcc -march=z13 -O0 wrong0.i -o a.out -w; ./a.out
1
clang -march=arch13 -O2 wrong0.i -o a.out -w; ./a.out
1
clang -march=arch13 -O1 wrong0.i -o a.out -w; ./a.out
0
This was run on SystemZ, but it should probably run the same on other
architectures...
long a, e;
long *b = &a;
int c, d;
int main() {
int f = -1452951746;
long *g = &e;
h:
i:
if (((0 != 8) != (*g = (f >= (-(unsigned)f)))) || b)
;
else {
int j;
for (; 7;) {
char k;
d = 0;
for (; d; d--)
for (; c;)
f = 0;
for (; 0;)
goto h;
if (c)
goto i;
b = 0;
}
}
printf("%d\n", ((int) e));
}
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