https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83541
Bug ID: 83541
Summary: Missed optimization with int overflow
Product: gcc
Version: tree-ssa
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zamazan4ik at tut dot by
Target Milestone: ---
gcc(trunk) with '-O3 -std=c++17 -ffast-math' for this:
#include <limits>
int test(int x)
{
if(x == std::numeric_limits<int>::max())
{
return x+1;
}
return 42;
}
generates this:
test(int):
cmp edi, 2147483647
mov edx, -2147483648
mov eax, 42
cmove eax, edx
ret
But branch with condition is UB, so you can just delete it and simply return
42.
