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3a4a884c16
all values belonging to the intersection will belong to the resulting range. The former was inconsistent about that point (either way is fine, just pick one.) This is part of PR4545. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76289 91177308-0d34-0410-b5e6-96231b3b80d8
299 lines
11 KiB
C++
299 lines
11 KiB
C++
//===- LoopVR.cpp - Value Range analysis driven by loop information -------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// FIXME: What does this do?
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "loopvr"
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#include "llvm/Analysis/LoopVR.h"
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#include "llvm/Constants.h"
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#include "llvm/Instructions.h"
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#include "llvm/LLVMContext.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/Assembly/Writer.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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char LoopVR::ID = 0;
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static RegisterPass<LoopVR> X("loopvr", "Loop Value Ranges", false, true);
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/// getRange - determine the range for a particular SCEV within a given Loop
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ConstantRange LoopVR::getRange(const SCEV *S, Loop *L, ScalarEvolution &SE) {
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const SCEV *T = SE.getBackedgeTakenCount(L);
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if (isa<SCEVCouldNotCompute>(T))
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return ConstantRange(cast<IntegerType>(S->getType())->getBitWidth(), true);
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T = SE.getTruncateOrZeroExtend(T, S->getType());
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return getRange(S, T, SE);
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}
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/// getRange - determine the range for a particular SCEV with a given trip count
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ConstantRange LoopVR::getRange(const SCEV *S, const SCEV *T, ScalarEvolution &SE){
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if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
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return ConstantRange(C->getValue()->getValue());
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ConstantRange FullSet(cast<IntegerType>(S->getType())->getBitWidth(), true);
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// {x,+,y,+,...z}. We detect overflow by checking the size of the set after
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// summing the upper and lower.
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if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
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ConstantRange X = getRange(Add->getOperand(0), T, SE);
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if (X.isFullSet()) return FullSet;
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for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i) {
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ConstantRange Y = getRange(Add->getOperand(i), T, SE);
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if (Y.isFullSet()) return FullSet;
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APInt Spread_X = X.getSetSize(), Spread_Y = Y.getSetSize();
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APInt NewLower = X.getLower() + Y.getLower();
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APInt NewUpper = X.getUpper() + Y.getUpper() - 1;
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if (NewLower == NewUpper)
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return FullSet;
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X = ConstantRange(NewLower, NewUpper);
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if (X.getSetSize().ult(Spread_X) || X.getSetSize().ult(Spread_Y))
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return FullSet; // we've wrapped, therefore, full set.
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}
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return X;
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}
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// {x,*,y,*,...,z}. In order to detect overflow, we use k*bitwidth where
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// k is the number of terms being multiplied.
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if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
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ConstantRange X = getRange(Mul->getOperand(0), T, SE);
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if (X.isFullSet()) return FullSet;
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const IntegerType *Ty = Context->getIntegerType(X.getBitWidth());
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const IntegerType *ExTy = Context->getIntegerType(X.getBitWidth() *
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Mul->getNumOperands());
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ConstantRange XExt = X.zeroExtend(ExTy->getBitWidth());
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for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i) {
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ConstantRange Y = getRange(Mul->getOperand(i), T, SE);
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if (Y.isFullSet()) return FullSet;
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ConstantRange YExt = Y.zeroExtend(ExTy->getBitWidth());
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XExt = ConstantRange(XExt.getLower() * YExt.getLower(),
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((XExt.getUpper()-1) * (YExt.getUpper()-1)) + 1);
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}
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return XExt.truncate(Ty->getBitWidth());
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}
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// X smax Y smax ... Z is: range(smax(X_smin, Y_smin, ..., Z_smin),
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// smax(X_smax, Y_smax, ..., Z_smax))
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// It doesn't matter if one of the SCEVs has FullSet because we're taking
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// a maximum of the minimums across all of them.
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if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
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ConstantRange X = getRange(SMax->getOperand(0), T, SE);
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if (X.isFullSet()) return FullSet;
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APInt smin = X.getSignedMin(), smax = X.getSignedMax();
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for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i) {
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ConstantRange Y = getRange(SMax->getOperand(i), T, SE);
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smin = APIntOps::smax(smin, Y.getSignedMin());
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smax = APIntOps::smax(smax, Y.getSignedMax());
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}
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if (smax + 1 == smin) return FullSet;
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return ConstantRange(smin, smax + 1);
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}
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// X umax Y umax ... Z is: range(umax(X_umin, Y_umin, ..., Z_umin),
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// umax(X_umax, Y_umax, ..., Z_umax))
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// It doesn't matter if one of the SCEVs has FullSet because we're taking
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// a maximum of the minimums across all of them.
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if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
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ConstantRange X = getRange(UMax->getOperand(0), T, SE);
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if (X.isFullSet()) return FullSet;
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APInt umin = X.getUnsignedMin(), umax = X.getUnsignedMax();
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for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i) {
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ConstantRange Y = getRange(UMax->getOperand(i), T, SE);
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umin = APIntOps::umax(umin, Y.getUnsignedMin());
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umax = APIntOps::umax(umax, Y.getUnsignedMax());
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}
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if (umax + 1 == umin) return FullSet;
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return ConstantRange(umin, umax + 1);
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}
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// L udiv R. Luckily, there's only ever 2 sides to a udiv.
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if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
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ConstantRange L = getRange(UDiv->getLHS(), T, SE);
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ConstantRange R = getRange(UDiv->getRHS(), T, SE);
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if (L.isFullSet() && R.isFullSet()) return FullSet;
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if (R.getUnsignedMax() == 0) {
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// RHS must be single-element zero. Return an empty set.
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return ConstantRange(R.getBitWidth(), false);
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}
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APInt Lower = L.getUnsignedMin().udiv(R.getUnsignedMax());
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APInt Upper;
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if (R.getUnsignedMin() == 0) {
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// Just because it contains zero, doesn't mean it will also contain one.
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ConstantRange NotZero(APInt(L.getBitWidth(), 1),
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APInt::getNullValue(L.getBitWidth()));
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R = R.intersectWith(NotZero);
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}
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// But, the intersection might still include zero. If it does, then we know
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// it also included one.
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if (R.contains(APInt::getNullValue(L.getBitWidth())))
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Upper = L.getUnsignedMax();
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else
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Upper = L.getUnsignedMax().udiv(R.getUnsignedMin());
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return ConstantRange(Lower, Upper);
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}
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// ConstantRange already implements the cast operators.
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if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
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T = SE.getTruncateOrZeroExtend(T, ZExt->getOperand()->getType());
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ConstantRange X = getRange(ZExt->getOperand(), T, SE);
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return X.zeroExtend(cast<IntegerType>(ZExt->getType())->getBitWidth());
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}
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if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
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T = SE.getTruncateOrZeroExtend(T, SExt->getOperand()->getType());
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ConstantRange X = getRange(SExt->getOperand(), T, SE);
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return X.signExtend(cast<IntegerType>(SExt->getType())->getBitWidth());
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}
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if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
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T = SE.getTruncateOrZeroExtend(T, Trunc->getOperand()->getType());
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ConstantRange X = getRange(Trunc->getOperand(), T, SE);
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if (X.isFullSet()) return FullSet;
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return X.truncate(cast<IntegerType>(Trunc->getType())->getBitWidth());
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}
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if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
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const SCEVConstant *Trip = dyn_cast<SCEVConstant>(T);
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if (!Trip) return FullSet;
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if (AddRec->isAffine()) {
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const SCEV *StartHandle = AddRec->getStart();
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const SCEV *StepHandle = AddRec->getOperand(1);
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const SCEVConstant *Step = dyn_cast<SCEVConstant>(StepHandle);
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if (!Step) return FullSet;
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uint32_t ExWidth = 2 * Trip->getValue()->getBitWidth();
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APInt TripExt = Trip->getValue()->getValue(); TripExt.zext(ExWidth);
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APInt StepExt = Step->getValue()->getValue(); StepExt.zext(ExWidth);
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if ((TripExt * StepExt).ugt(APInt::getLowBitsSet(ExWidth, ExWidth >> 1)))
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return FullSet;
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const SCEV *EndHandle = SE.getAddExpr(StartHandle,
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SE.getMulExpr(T, StepHandle));
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const SCEVConstant *Start = dyn_cast<SCEVConstant>(StartHandle);
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const SCEVConstant *End = dyn_cast<SCEVConstant>(EndHandle);
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if (!Start || !End) return FullSet;
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const APInt &StartInt = Start->getValue()->getValue();
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const APInt &EndInt = End->getValue()->getValue();
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const APInt &StepInt = Step->getValue()->getValue();
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if (StepInt.isNegative()) {
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if (EndInt == StartInt + 1) return FullSet;
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return ConstantRange(EndInt, StartInt + 1);
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} else {
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if (StartInt == EndInt + 1) return FullSet;
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return ConstantRange(StartInt, EndInt + 1);
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}
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}
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}
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// TODO: non-affine addrec, udiv, SCEVUnknown (narrowed from elsewhere)?
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return FullSet;
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}
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void LoopVR::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequiredTransitive<LoopInfo>();
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AU.addRequiredTransitive<ScalarEvolution>();
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AU.setPreservesAll();
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}
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bool LoopVR::runOnFunction(Function &F) { Map.clear(); return false; }
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void LoopVR::print(std::ostream &os, const Module *) const {
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raw_os_ostream OS(os);
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for (std::map<Value *, ConstantRange *>::const_iterator I = Map.begin(),
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E = Map.end(); I != E; ++I) {
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OS << *I->first << ": " << *I->second << '\n';
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}
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}
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void LoopVR::releaseMemory() {
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for (std::map<Value *, ConstantRange *>::iterator I = Map.begin(),
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E = Map.end(); I != E; ++I) {
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delete I->second;
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}
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Map.clear();
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}
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ConstantRange LoopVR::compute(Value *V) {
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if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
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return ConstantRange(CI->getValue());
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Instruction *I = dyn_cast<Instruction>(V);
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if (!I)
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return ConstantRange(cast<IntegerType>(V->getType())->getBitWidth(), false);
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LoopInfo &LI = getAnalysis<LoopInfo>();
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Loop *L = LI.getLoopFor(I->getParent());
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if (!L || L->isLoopInvariant(I))
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return ConstantRange(cast<IntegerType>(V->getType())->getBitWidth(), false);
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ScalarEvolution &SE = getAnalysis<ScalarEvolution>();
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const SCEV *S = SE.getSCEV(I);
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if (isa<SCEVUnknown>(S) || isa<SCEVCouldNotCompute>(S))
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return ConstantRange(cast<IntegerType>(V->getType())->getBitWidth(), false);
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return ConstantRange(getRange(S, L, SE));
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}
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ConstantRange LoopVR::get(Value *V) {
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std::map<Value *, ConstantRange *>::iterator I = Map.find(V);
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if (I == Map.end()) {
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ConstantRange *CR = new ConstantRange(compute(V));
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Map[V] = CR;
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return *CR;
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}
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return *I->second;
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}
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void LoopVR::remove(Value *V) {
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std::map<Value *, ConstantRange *>::iterator I = Map.find(V);
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if (I != Map.end()) {
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delete I->second;
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Map.erase(I);
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}
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}
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void LoopVR::narrow(Value *V, const ConstantRange &CR) {
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if (CR.isFullSet()) return;
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std::map<Value *, ConstantRange *>::iterator I = Map.find(V);
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if (I == Map.end())
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Map[V] = new ConstantRange(CR);
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else
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Map[V] = new ConstantRange(Map[V]->intersectWith(CR));
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}
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