https://bugs.llvm.org/show_bug.cgi?id=45682
Bug ID: 45682
Summary: Failure to optimize some limit bounds patterns based
on __builtin_assume
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: gabrav...@gmail.com
CC: llvm-bugs@lists.llvm.org
#include <limits.h>
#ifdef __clang__
#define assume __builtin_assume
#else
inline void assume(bool x)
{
if (!x)
__builtin_unreachable();
}
#endif
void g();
void f(int x, int y)
{
assume(y > 0);
x += y;
if (x == -INT_MAX - 1)
g();
}
`f` is optimized to doing nothing by gcc, clang does the check even though `y >
0` means the last condition is always false. Sample comparison here :
https://godbolt.org/z/x-cuqX
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