ICI.getPredicate() == ICmpInst::ICMP_EQ ? ICmpInst::ICMP_UGT
: ICmpInst::ICMP_ULE,
LHSI->getOperand(0), SubOne(RHS));
+
+ // (icmp eq (and %A, C), 0) -> (icmp sgt (trunc %A), -1)
+ // iff C is a power of 2
+ if (ICI.isEquality() && LHSI->hasOneUse() && match(RHS, m_Zero())) {
+ if (auto *CI = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
+ const APInt &AI = CI->getValue();
+ int32_t ExactLogBase2 = AI.exactLogBase2();
+ if (ExactLogBase2 != -1 && DL.isLegalInteger(ExactLogBase2 + 1)) {
+ Type *NTy = IntegerType::get(ICI.getContext(), ExactLogBase2 + 1);
+ Value *Trunc = Builder->CreateTrunc(LHSI->getOperand(0), NTy);
+ return new ICmpInst(ICI.getPredicate() == ICmpInst::ICMP_EQ
+ ? ICmpInst::ICMP_SGE
+ : ICmpInst::ICMP_SLT,
+ Trunc, Constant::getNullValue(NTy));
+ }
+ }
+ }
break;
case Instruction::Or: {
Value *TruncA = Builder->CreateTrunc(A, NewType, A->getName()+".trunc");
Value *TruncB = Builder->CreateTrunc(B, NewType, B->getName()+".trunc");
- CallInst *Call = Builder->CreateCall2(F, TruncA, TruncB, "sadd");
+ CallInst *Call = Builder->CreateCall(F, {TruncA, TruncB}, "sadd");
Value *Add = Builder->CreateExtractValue(Call, 0, "sadd.result");
Value *ZExt = Builder->CreateZExt(Add, OrigAdd->getType());
return ExtractValueInst::Create(Call, 1, "sadd.overflow");
}
-static Instruction *ProcessUAddIdiom(Instruction &I, Value *OrigAddV,
- InstCombiner &IC) {
- // Don't bother doing this transformation for pointers, don't do it for
- // vectors.
- if (!isa<IntegerType>(OrigAddV->getType())) return nullptr;
+bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
+ Value *RHS, Instruction &OrigI,
+ Value *&Result, Constant *&Overflow) {
+ if (OrigI.isCommutative() && isa<Constant>(LHS) && !isa<Constant>(RHS))
+ std::swap(LHS, RHS);
+
+ auto SetResult = [&](Value *OpResult, Constant *OverflowVal, bool ReuseName) {
+ Result = OpResult;
+ Overflow = OverflowVal;
+ if (ReuseName)
+ Result->takeName(&OrigI);
+ return true;
+ };
- // If the add is a constant expr, then we don't bother transforming it.
- Instruction *OrigAdd = dyn_cast<Instruction>(OrigAddV);
- if (!OrigAdd) return nullptr;
+ switch (OCF) {
+ case OCF_INVALID:
+ llvm_unreachable("bad overflow check kind!");
- Value *LHS = OrigAdd->getOperand(0), *RHS = OrigAdd->getOperand(1);
+ case OCF_UNSIGNED_ADD: {
+ OverflowResult OR = computeOverflowForUnsignedAdd(LHS, RHS, &OrigI);
+ if (OR == OverflowResult::NeverOverflows)
+ return SetResult(Builder->CreateNUWAdd(LHS, RHS), Builder->getFalse(),
+ true);
- // Put the new code above the original add, in case there are any uses of the
- // add between the add and the compare.
- InstCombiner::BuilderTy *Builder = IC.Builder;
- Builder->SetInsertPoint(OrigAdd);
+ if (OR == OverflowResult::AlwaysOverflows)
+ return SetResult(Builder->CreateAdd(LHS, RHS), Builder->getTrue(), true);
+ }
+ // FALL THROUGH uadd into sadd
+ case OCF_SIGNED_ADD: {
+ // X + 0 -> {X, false}
+ if (match(RHS, m_Zero()))
+ return SetResult(LHS, Builder->getFalse(), false);
+
+ // We can strength reduce this signed add into a regular add if we can prove
+ // that it will never overflow.
+ if (OCF == OCF_SIGNED_ADD)
+ if (WillNotOverflowSignedAdd(LHS, RHS, OrigI))
+ return SetResult(Builder->CreateNSWAdd(LHS, RHS), Builder->getFalse(),
+ true);
+ break;
+ }
- Module *M = I.getParent()->getParent()->getParent();
- Type *Ty = LHS->getType();
- Value *F = Intrinsic::getDeclaration(M, Intrinsic::uadd_with_overflow, Ty);
- CallInst *Call = Builder->CreateCall2(F, LHS, RHS, "uadd");
- Value *Add = Builder->CreateExtractValue(Call, 0);
+ case OCF_UNSIGNED_SUB:
+ case OCF_SIGNED_SUB: {
+ // X - 0 -> {X, false}
+ if (match(RHS, m_Zero()))
+ return SetResult(LHS, Builder->getFalse(), false);
+
+ if (OCF == OCF_SIGNED_SUB) {
+ if (WillNotOverflowSignedSub(LHS, RHS, OrigI))
+ return SetResult(Builder->CreateNSWSub(LHS, RHS), Builder->getFalse(),
+ true);
+ } else {
+ if (WillNotOverflowUnsignedSub(LHS, RHS, OrigI))
+ return SetResult(Builder->CreateNUWSub(LHS, RHS), Builder->getFalse(),
+ true);
+ }
+ break;
+ }
- IC.ReplaceInstUsesWith(*OrigAdd, Add);
+ case OCF_UNSIGNED_MUL: {
+ OverflowResult OR = computeOverflowForUnsignedMul(LHS, RHS, &OrigI);
+ if (OR == OverflowResult::NeverOverflows)
+ return SetResult(Builder->CreateNUWMul(LHS, RHS), Builder->getFalse(),
+ true);
+ if (OR == OverflowResult::AlwaysOverflows)
+ return SetResult(Builder->CreateMul(LHS, RHS), Builder->getTrue(), true);
+ } // FALL THROUGH
+ case OCF_SIGNED_MUL:
+ // X * undef -> undef
+ if (isa<UndefValue>(RHS))
+ return SetResult(RHS, UndefValue::get(Builder->getInt1Ty()), false);
+
+ // X * 0 -> {0, false}
+ if (match(RHS, m_Zero()))
+ return SetResult(RHS, Builder->getFalse(), false);
+
+ // X * 1 -> {X, false}
+ if (match(RHS, m_One()))
+ return SetResult(LHS, Builder->getFalse(), false);
+
+ if (OCF == OCF_SIGNED_MUL)
+ if (WillNotOverflowSignedMul(LHS, RHS, OrigI))
+ return SetResult(Builder->CreateNSWMul(LHS, RHS), Builder->getFalse(),
+ true);
+ break;
+ }
- // The original icmp gets replaced with the overflow value.
- return ExtractValueInst::Create(Call, 1, "uadd.overflow");
+ return false;
}
/// \brief Recognize and process idiom involving test for multiplication
MulB = Builder->CreateZExt(B, MulType);
Value *F =
Intrinsic::getDeclaration(M, Intrinsic::umul_with_overflow, MulType);
- CallInst *Call = Builder->CreateCall2(F, MulA, MulB, "umul");
+ CallInst *Call = Builder->CreateCall(F, {MulA, MulB}, "umul");
IC.Worklist.Add(MulInstr);
// If there are uses of mul result other than the comparison, we know that
Changed = true;
}
- if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, DL, TLI, DT, AC))
+ if (Value *V =
+ SimplifyICmpInst(I.getPredicate(), Op0, Op1, DL, TLI, DT, AC, &I))
return ReplaceInstUsesWith(I, V);
// comparing -val or val with non-zero is the same as just comparing val
return new ICmpInst(I.getPredicate(), ConstantExpr::getNot(RHSC), A);
}
- // (a+b) <u a --> llvm.uadd.with.overflow.
- // (a+b) <u b --> llvm.uadd.with.overflow.
- if (I.getPredicate() == ICmpInst::ICMP_ULT &&
- match(Op0, m_Add(m_Value(A), m_Value(B))) &&
- (Op1 == A || Op1 == B))
- if (Instruction *R = ProcessUAddIdiom(I, Op0, *this))
- return R;
-
- // a >u (a+b) --> llvm.uadd.with.overflow.
- // b >u (a+b) --> llvm.uadd.with.overflow.
- if (I.getPredicate() == ICmpInst::ICMP_UGT &&
- match(Op1, m_Add(m_Value(A), m_Value(B))) &&
- (Op0 == A || Op0 == B))
- if (Instruction *R = ProcessUAddIdiom(I, Op1, *this))
- return R;
+ Instruction *AddI = nullptr;
+ if (match(&I, m_UAddWithOverflow(m_Value(A), m_Value(B),
+ m_Instruction(AddI))) &&
+ isa<IntegerType>(A->getType())) {
+ Value *Result;
+ Constant *Overflow;
+ if (OptimizeOverflowCheck(OCF_UNSIGNED_ADD, A, B, *AddI, Result,
+ Overflow)) {
+ ReplaceInstUsesWith(*AddI, Result);
+ return ReplaceInstUsesWith(I, Overflow);
+ }
+ }
// (zext a) * (zext b) --> llvm.umul.with.overflow.
if (match(Op0, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
}
}
+ // (A << C) == (B << C) --> ((A^B) & (~0U >> C)) == 0
+ if (match(Op0, m_OneUse(m_Shl(m_Value(A), m_ConstantInt(Cst1)))) &&
+ match(Op1, m_OneUse(m_Shl(m_Value(B), m_Specific(Cst1))))) {
+ unsigned TypeBits = Cst1->getBitWidth();
+ unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
+ if (ShAmt < TypeBits && ShAmt != 0) {
+ Value *Xor = Builder->CreateXor(A, B, I.getName() + ".unshifted");
+ APInt AndVal = APInt::getLowBitsSet(TypeBits, TypeBits - ShAmt);
+ Value *And = Builder->CreateAnd(Xor, Builder->getInt(AndVal),
+ I.getName() + ".mask");
+ return new ICmpInst(I.getPredicate(), And,
+ Constant::getNullValue(Cst1->getType()));
+ }
+ }
+
// Transform "icmp eq (trunc (lshr(X, cst1)), cst" to
// "icmp (and X, mask), cst"
uint64_t ShAmt = 0;
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
- if (Value *V = SimplifyFCmpInst(I.getPredicate(), Op0, Op1, DL, TLI, DT, AC))
+ if (Value *V = SimplifyFCmpInst(I.getPredicate(), Op0, Op1,
+ I.getFastMathFlags(), DL, TLI, DT, AC, &I))
return ReplaceInstUsesWith(I, V);
// Simplify 'fcmp pred X, X'
}
}
+ // Test if the FCmpInst instruction is used exclusively by a select as
+ // part of a minimum or maximum operation. If so, refrain from doing
+ // any other folding. This helps out other analyses which understand
+ // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
+ // and CodeGen. And in this case, at least one of the comparison
+ // operands has at least one user besides the compare (the select),
+ // which would often largely negate the benefit of folding anyway.
+ if (I.hasOneUse())
+ if (SelectInst *SI = dyn_cast<SelectInst>(*I.user_begin()))
+ if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) ||
+ (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1))
+ return nullptr;
+
// Handle fcmp with constant RHS
if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
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