https://bugs.llvm.org/show_bug.cgi?id=50389
Bug ID: 50389
Summary: Missed optimization for A && !B
Product: clang
Version: trunk
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P
Component: C++
Assignee: unassignedclangb...@nondot.org
Reporter: mv...@google.com
CC: blitzrak...@gmail.com, dgre...@apple.com,
erik.pilking...@gmail.com, llvm-bugs@lists.llvm.org,
richard-l...@metafoo.co.uk
The ABI dictates that bool be strictly 0 or 1. A bool value outside of 0 or 1
is UB
The compiler can optimize `A && !B1 then as `A > B`, which say under x86
becomes the macro fused op:
AAndNotBAlt(bool, bool):
cmp dil, sil
jbe .LBB1_1
instead, the compiler generates:
https://gcc.godbolt.org/z/EWx63b4nz
AAndNotB(bool, bool):
test edi, edi
je .LBB0_2
test sil, sil
jne .LBB0_2
jmp True()
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