Why should I know this?

https://github.com/llvm/llvm-project/pull/91762 (기억을 보존하기 위한) 패치 내용 정리.패치 동기LLVM에서는 AND/OR/XOR 연산을 BitwiseLogic 이라고 부른다. 해당 로직들은 특정 상황에서 최적화 될 수 있다.다음의 경우를 보자.define i32 @src_no_trans_select_or_eq0_and_or(i32 %x, i32 %y) {; CHECK-LABEL: @src_no_trans_select_or_eq0_and_or(; CHECK-NEXT: [[OR:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]; CHECK-NEXT: ret i32 [[OR]]; %or = or i32 %x, %y %or0 = icmp eq..

https://die4taoam.tistory.com/147 computeKnownBits & KnownBits 관련 예제computeKnownBits https://llvm.org/doxygen/ValueTracking_8cpp.html#a903bd19e9d31beff55b22fe86111639e Determine which bits of V are known to be either zero or one and return them. void computeKnownBits (const Value *V, KnownBits &Known, const DataLayout &DL,die4taoam.tistory.com  computeKnownBitsㄴ computeKnownBitsFromContext    ㄴ ..

다음 코드를 통해 computeKnownBitsFromCmp 에서 KnownBit를 추산하는 방식을 알아보자. unsigned BitWidth = Known.getBitWidth(); auto m_V = m_CombineOr(m_Specific(V), m_PtrToIntSameSize(Q.DL, m_Specific(V))); Value *Y; const APInt *Mask, *C; uint64_t ShAmt; switch (Pred) { case ICmpInst::ICMP_EQ: // assume(V = C) if (match(LHS, m_V) && match(RHS, m_APInt(C))) { Known = Known.unionWith(KnownBits::ma..

computeKnownBitsFromCondㄴ computeKnownBitsFromICmpCond void llvm::computeKnownBitsFromICmpCond(const Value *V, ICmpInst *Cmp, KnownBits &Known, const SimplifyQuery &SQ, bool Invert) { ICmpInst::Predicate Pred = Invert ? Cmp->getInversePredicate() : Cmp->getPredicate(); Value *LHS = Cmp->getOperand(0); Value *..

(TBD)