https://bugs.llvm.org/show_bug.cgi?id=35725
Bug ID: 35725
Summary: Missed optimization with int overflow
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: LLVM Codegen
Assignee: unassignedclangb...@nondot.org
Reporter: zamazan...@tut.by
CC: llvm-bugs@lists.llvm.org
clang(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): # @test(int)
lea ecx, [rdi + 1]
cmp edi, 2147483647
mov eax, 42
cmove eax, ecx
ret
But branch with condition is UB, so you can just delete it and simply return
42.
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