X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FValueTracking.cpp;h=6f58afe527906428fddb9659e6b40eadac6789b8;hb=124708d9b47cc53cb11d8bfed75b241b6eec86d4;hp=7ab4d2ba04c031fd24e1f4a23429e09ff698cabf;hpb=7a874ddda037349184fbeb22838cc11a1a9bb78f;p=oota-llvm.git diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index 7ab4d2ba04c..6f58afe5279 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -13,6 +13,7 @@ //===----------------------------------------------------------------------===// #include "llvm/Analysis/ValueTracking.h" +#include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Constants.h" #include "llvm/Instructions.h" #include "llvm/GlobalVariable.h" @@ -255,14 +256,13 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, else SrcBitWidth = SrcTy->getScalarSizeInBits(); - APInt MaskIn(Mask); - MaskIn.zextOrTrunc(SrcBitWidth); - KnownZero.zextOrTrunc(SrcBitWidth); - KnownOne.zextOrTrunc(SrcBitWidth); + APInt MaskIn = Mask.zextOrTrunc(SrcBitWidth); + KnownZero = KnownZero.zextOrTrunc(SrcBitWidth); + KnownOne = KnownOne.zextOrTrunc(SrcBitWidth); ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, TD, Depth+1); - KnownZero.zextOrTrunc(BitWidth); - KnownOne.zextOrTrunc(BitWidth); + KnownZero = KnownZero.zextOrTrunc(BitWidth); + KnownOne = KnownOne.zextOrTrunc(BitWidth); // Any top bits are known to be zero. if (BitWidth > SrcBitWidth) KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth); @@ -284,15 +284,14 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, // Compute the bits in the result that are not present in the input. unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits(); - APInt MaskIn(Mask); - MaskIn.trunc(SrcBitWidth); - KnownZero.trunc(SrcBitWidth); - KnownOne.trunc(SrcBitWidth); + APInt MaskIn = Mask.trunc(SrcBitWidth); + KnownZero = KnownZero.trunc(SrcBitWidth); + KnownOne = KnownOne.trunc(SrcBitWidth); ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, TD, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); - KnownZero.zext(BitWidth); - KnownOne.zext(BitWidth); + KnownZero = KnownZero.zext(BitWidth); + KnownOne = KnownOne.zext(BitWidth); // If the sign bit of the input is known set or clear, then we know the // top bits of the result. @@ -679,6 +678,13 @@ unsigned llvm::ComputeNumSignBits(Value *V, const TargetData *TD, Tmp += C->getZExtValue(); if (Tmp > TyBits) Tmp = TyBits; } + // vector ashr X, -> adds C sign bits + if (ConstantVector *C = dyn_cast(U->getOperand(1))) { + if (ConstantInt *CI = dyn_cast_or_null(C->getSplatValue())) { + Tmp += CI->getZExtValue(); + if (Tmp > TyBits) Tmp = TyBits; + } + } return Tmp; case Instruction::Shl: if (ConstantInt *C = dyn_cast(U->getOperand(1))) { @@ -983,6 +989,75 @@ bool llvm::CannotBeNegativeZero(const Value *V, unsigned Depth) { return false; } +/// isBytewiseValue - 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, +/// i16 0xF0F0, double 0.0 etc. If the value can't be handled with a repeated +/// byte store (e.g. i16 0x1234), return null. +Value *llvm::isBytewiseValue(Value *V) { + // All byte-wide stores are splatable, even of arbitrary variables. + if (V->getType()->isIntegerTy(8)) return V; + + // Constant float and double values can be handled as integer values if the + // corresponding integer value is "byteable". An important case is 0.0. + if (ConstantFP *CFP = dyn_cast(V)) { + if (CFP->getType()->isFloatTy()) + V = ConstantExpr::getBitCast(CFP, Type::getInt32Ty(V->getContext())); + if (CFP->getType()->isDoubleTy()) + V = ConstantExpr::getBitCast(CFP, Type::getInt64Ty(V->getContext())); + // 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. + 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 0; + } + return ConstantInt::get(V->getContext(), Val); + } + } + + // A ConstantArray is splatable if all its members are equal and also + // splatable. + if (ConstantArray *CA = dyn_cast(V)) { + if (CA->getNumOperands() == 0) + return 0; + + Value *Val = isBytewiseValue(CA->getOperand(0)); + if (!Val) + return 0; + + for (unsigned I = 1, E = CA->getNumOperands(); I != E; ++I) + if (CA->getOperand(I-1) != CA->getOperand(I)) + return 0; + + return Val; + } + + // Conceptually, we could handle things like: + // %a = zext i8 %X to i16 + // %b = shl i16 %a, 8 + // %c = or i16 %a, %b + // but until there is an example that actually needs this, it doesn't seem + // worth worrying about. + return 0; +} + + // This is the recursive version of BuildSubAggregate. It takes a few different // arguments. Idxs is the index within the nested struct From that we are // looking at now (which is of type IndexedType). IdxSkip is the number of @@ -1428,3 +1503,31 @@ uint64_t llvm::GetStringLength(Value *V) { // an empty string as a length. return Len == ~0ULL ? 1 : Len; } + +Value *llvm::GetUnderlyingObject(Value *V, unsigned MaxLookup) { + if (!V->getType()->isPointerTy()) + return V; + for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) { + if (GEPOperator *GEP = dyn_cast(V)) { + V = GEP->getPointerOperand(); + } else if (Operator::getOpcode(V) == Instruction::BitCast) { + V = cast(V)->getOperand(0); + } else if (GlobalAlias *GA = dyn_cast(V)) { + if (GA->mayBeOverridden()) + return V; + V = GA->getAliasee(); + } else { + // See if InstructionSimplify knows any relevant tricks. + if (Instruction *I = dyn_cast(V)) + // TODO: Aquire TargetData and DominatorTree and use them. + if (Value *Simplified = SimplifyInstruction(I, 0, 0)) { + V = Simplified; + continue; + } + + return V; + } + assert(V->getType()->isPointerTy() && "Unexpected operand type!"); + } + return V; +}