From 7c7121edb9d3560cdc0b57f20212176c0697ec51 Mon Sep 17 00:00:00 2001 From: Rafael Espindola Date: Fri, 30 Mar 2012 15:52:11 +0000 Subject: Add computeMaskedBitsLoad back, as it was the change to instsimplify that caused the slowdown last time. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153747 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/ValueTracking.cpp | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index 01e00caa3b..17bad941e5 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -20,8 +20,10 @@ #include "llvm/GlobalAlias.h" #include "llvm/IntrinsicInst.h" #include "llvm/LLVMContext.h" +#include "llvm/Metadata.h" #include "llvm/Operator.h" #include "llvm/Target/TargetData.h" +#include "llvm/Support/ConstantRange.h" #include "llvm/Support/GetElementPtrTypeIterator.h" #include "llvm/Support/MathExtras.h" #include "llvm/Support/PatternMatch.h" @@ -195,6 +197,26 @@ static void ComputeMaskedBitsMul(Value *Op0, Value *Op1, bool NSW, KnownOne.setBit(BitWidth - 1); } +static void computeMaskedBitsLoad(const MDNode &Ranges, const APInt &Mask, + APInt &KnownZero) { + unsigned BitWidth = Mask.getBitWidth(); + unsigned NumRanges = Ranges.getNumOperands() / 2; + assert(NumRanges >= 1); + + // Use the high end of the ranges to find leading zeros. + unsigned MinLeadingZeros = BitWidth; + for (unsigned i = 0; i < NumRanges; ++i) { + ConstantInt *Lower = cast(Ranges.getOperand(2*i + 0)); + ConstantInt *Upper = cast(Ranges.getOperand(2*i + 1)); + ConstantRange Range(Lower->getValue(), Upper->getValue()); + if (Range.isWrappedSet()) + MinLeadingZeros = 0; // -1 has no zeros + unsigned LeadingZeros = (Upper->getValue() - 1).countLeadingZeros(); + MinLeadingZeros = std::min(LeadingZeros, MinLeadingZeros); + } + + KnownZero = Mask & APInt::getHighBitsSet(BitWidth, MinLeadingZeros); +} /// ComputeMaskedBits - Determine which of the bits specified in Mask are /// known to be either zero or one and return them in the KnownZero/KnownOne /// bit sets. This code only analyzes bits in Mask, in order to short-circuit @@ -315,6 +337,10 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask, APInt KnownZero2(KnownZero), KnownOne2(KnownOne); switch (I->getOpcode()) { default: break; + case Instruction::Load: + if (MDNode *MD = cast(I)->getMetadata(LLVMContext::MD_range)) + computeMaskedBitsLoad(*MD, Mask, KnownZero); + return; case Instruction::And: { // If either the LHS or the RHS are Zero, the result is zero. ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1); -- cgit v1.2.3-18-g5258