X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FValueTracking.cpp;h=5ae8574ebe13e74478b72ffd5a325273b0ab2b5e;hb=4db669fb26764b55bd9c0b8b2c2b917b135efe24;hp=bba2f9f2735c8328062f9036a6ad224481714b78;hpb=186c5ccb074ee1c4ef2603543921c955f184a15e;p=oota-llvm.git diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index bba2f9f2735..5ae8574ebe1 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -13,8 +13,8 @@ //===----------------------------------------------------------------------===// #include "llvm/Analysis/ValueTracking.h" -#include "llvm/Analysis/AssumptionCache.h" #include "llvm/ADT/SmallPtrSet.h" +#include "llvm/Analysis/AssumptionCache.h" #include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Analysis/MemoryBuiltins.h" #include "llvm/IR/CallSite.h" @@ -2044,6 +2044,59 @@ bool llvm::CannotBeNegativeZero(const Value *V, unsigned Depth) { return false; } +bool llvm::CannotBeOrderedLessThanZero(const Value *V, unsigned Depth) { + if (const ConstantFP *CFP = dyn_cast(V)) + return !CFP->getValueAPF().isNegative() || CFP->getValueAPF().isZero(); + + if (Depth == 6) + return false; // Limit search depth. + + const Operator *I = dyn_cast(V); + if (!I) return false; + + switch (I->getOpcode()) { + default: break; + case Instruction::FMul: + // x*x is always non-negative or a NaN. + if (I->getOperand(0) == I->getOperand(1)) + return true; + // Fall through + case Instruction::FAdd: + case Instruction::FDiv: + case Instruction::FRem: + return CannotBeOrderedLessThanZero(I->getOperand(0), Depth+1) && + CannotBeOrderedLessThanZero(I->getOperand(1), Depth+1); + case Instruction::FPExt: + case Instruction::FPTrunc: + // Widening/narrowing never change sign. + return CannotBeOrderedLessThanZero(I->getOperand(0), Depth+1); + case Instruction::Call: + if (const IntrinsicInst *II = dyn_cast(I)) + switch (II->getIntrinsicID()) { + default: break; + case Intrinsic::exp: + case Intrinsic::exp2: + case Intrinsic::fabs: + case Intrinsic::sqrt: + return true; + case Intrinsic::powi: + if (ConstantInt *CI = dyn_cast(I->getOperand(1))) { + // powi(x,n) is non-negative if n is even. + if (CI->getBitWidth() <= 64 && CI->getSExtValue() % 2u == 0) + return true; + } + return CannotBeOrderedLessThanZero(I->getOperand(0), Depth+1); + case Intrinsic::fma: + case Intrinsic::fmuladd: + // x*x+y is non-negative if y is non-negative. + return I->getOperand(0) == I->getOperand(1) && + CannotBeOrderedLessThanZero(I->getOperand(2), Depth+1); + } + break; + } + return false; +} + /// If the specified value can be set by repeating the same byte in memory, /// return the i8 value that it is represented with. This is /// true for all i8 values obviously, but is also true for i32 0, i32 -1, @@ -2068,26 +2121,16 @@ Value *llvm::isBytewiseValue(Value *V) { // Don't handle long double formats, which have strange constraints. } - // We can handle constant integers that are power of two in size and a - // multiple of 8 bits. + // We can handle constant integers that are multiple of 8 bits. if (ConstantInt *CI = dyn_cast(V)) { - unsigned Width = CI->getBitWidth(); - if (isPowerOf2_32(Width) && Width > 8) { - // We can handle this value if the recursive binary decomposition is the - // same at all levels. - APInt Val = CI->getValue(); - APInt Val2; - while (Val.getBitWidth() != 8) { - unsigned NextWidth = Val.getBitWidth()/2; - Val2 = Val.lshr(NextWidth); - Val2 = Val2.trunc(Val.getBitWidth()/2); - Val = Val.trunc(Val.getBitWidth()/2); - - // If the top/bottom halves aren't the same, reject it. - if (Val != Val2) - return nullptr; - } - return ConstantInt::get(V->getContext(), Val); + if (CI->getBitWidth() % 8 == 0) { + assert(CI->getBitWidth() > 8 && "8 bits should be handled above!"); + + // We can check that all bytes of an integer are equal by making use of a + // little trick: rotate by 8 and check if it's still the same value. + if (CI->getValue() != CI->getValue().rotl(8)) + return nullptr; + return ConstantInt::get(V->getContext(), CI->getValue().trunc(8)); } } @@ -2567,20 +2610,20 @@ bool llvm::isSafeToSpeculativelyExecute(const Value *V, case Instruction::SDiv: case Instruction::SRem: { // x / y is undefined if y == 0 or x == INT_MIN and y == -1 - const APInt *X, *Y; - if (match(Inst->getOperand(1), m_APInt(Y))) { - if (*Y != 0) { - if (*Y == -1) { - // The numerator can't be MinSignedValue if the denominator is -1. - if (match(Inst->getOperand(0), m_APInt(X))) - return !Y->isMinSignedValue(); - // The numerator *might* be MinSignedValue. - return false; - } - // The denominator is not 0 or -1, it's safe to proceed. - return true; - } - } + const APInt *Numerator, *Denominator; + if (!match(Inst->getOperand(1), m_APInt(Denominator))) + return false; + // We cannot hoist this division if the denominator is 0. + if (*Denominator == 0) + return false; + // It's safe to hoist if the denominator is not 0 or -1. + if (*Denominator != -1) + return true; + // At this point we know that the denominator is -1. It is safe to hoist as + // long we know that the numerator is not INT_MIN. + if (match(Inst->getOperand(0), m_APInt(Numerator))) + return !Numerator->isMinSignedValue(); + // The numerator *might* be MinSignedValue. return false; } case Instruction::Load: { @@ -2729,3 +2772,32 @@ OverflowResult llvm::computeOverflowForUnsignedMul(Value *LHS, Value *RHS, return OverflowResult::MayOverflow; } + +OverflowResult llvm::computeOverflowForUnsignedAdd(Value *LHS, Value *RHS, + const DataLayout *DL, + AssumptionCache *AC, + const Instruction *CxtI, + const DominatorTree *DT) { + bool LHSKnownNonNegative, LHSKnownNegative; + ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, DL, /*Depth=*/0, + AC, CxtI, DT); + if (LHSKnownNonNegative || LHSKnownNegative) { + bool RHSKnownNonNegative, RHSKnownNegative; + ComputeSignBit(RHS, RHSKnownNonNegative, RHSKnownNegative, DL, /*Depth=*/0, + AC, CxtI, DT); + + if (LHSKnownNegative && RHSKnownNegative) { + // The sign bit is set in both cases: this MUST overflow. + // Create a simple add instruction, and insert it into the struct. + return OverflowResult::AlwaysOverflows; + } + + if (LHSKnownNonNegative && RHSKnownNonNegative) { + // The sign bit is clear in both cases: this CANNOT overflow. + // Create a simple add instruction, and insert it into the struct. + return OverflowResult::NeverOverflows; + } + } + + return OverflowResult::MayOverflow; +}