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llvm-project/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
Yingwei Zheng acf86c5c4d [CVP] Keep ReachableCaseCount in sync with range of condition (#142302) 
https://github.com/llvm/llvm-project/pull/79993 assumes that a reachable
case must be contained by `CR`. However, it doesn't hold for some edge
cases. This patch adds additional checks to ensure `ReachableCaseCount`
is correct.

Note: Similar optimization in SCCP isn't affected by this bug because it
uses `CR` to compute `ReachableCaseCount`.

Closes https://github.com/llvm/llvm-project/issues/142286.
2025-06-11 15:55:43 -07:00

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//===- CorrelatedValuePropagation.cpp - Propagate CFG-derived info --------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the Correlated Value Propagation pass.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar/CorrelatedValuePropagation.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LazyValueInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
#include "llvm/Transforms/Utils/Local.h"
#include <cassert>
#include <optional>
#include <utility>
using namespace llvm;
#define DEBUG_TYPE "correlated-value-propagation"
STATISTIC(NumPhis, "Number of phis propagated");
STATISTIC(NumPhiCommon, "Number of phis deleted via common incoming value");
STATISTIC(NumSelects, "Number of selects propagated");
STATISTIC(NumCmps, "Number of comparisons propagated");
STATISTIC(NumReturns, "Number of return values propagated");
STATISTIC(NumDeadCases, "Number of switch cases removed");
STATISTIC(NumSDivSRemsNarrowed,
"Number of sdivs/srems whose width was decreased");
STATISTIC(NumSDivs, "Number of sdiv converted to udiv");
STATISTIC(NumUDivURemsNarrowed,
"Number of udivs/urems whose width was decreased");
STATISTIC(NumAShrsConverted, "Number of ashr converted to lshr");
STATISTIC(NumAShrsRemoved, "Number of ashr removed");
STATISTIC(NumSRems, "Number of srem converted to urem");
STATISTIC(NumSExt, "Number of sext converted to zext");
STATISTIC(NumSIToFP, "Number of sitofp converted to uitofp");
STATISTIC(NumSICmps, "Number of signed icmp preds simplified to unsigned");
STATISTIC(NumAnd, "Number of ands removed");
STATISTIC(NumNW, "Number of no-wrap deductions");
STATISTIC(NumNSW, "Number of no-signed-wrap deductions");
STATISTIC(NumNUW, "Number of no-unsigned-wrap deductions");
STATISTIC(NumAddNW, "Number of no-wrap deductions for add");
STATISTIC(NumAddNSW, "Number of no-signed-wrap deductions for add");
STATISTIC(NumAddNUW, "Number of no-unsigned-wrap deductions for add");
STATISTIC(NumSubNW, "Number of no-wrap deductions for sub");
STATISTIC(NumSubNSW, "Number of no-signed-wrap deductions for sub");
STATISTIC(NumSubNUW, "Number of no-unsigned-wrap deductions for sub");
STATISTIC(NumMulNW, "Number of no-wrap deductions for mul");
STATISTIC(NumMulNSW, "Number of no-signed-wrap deductions for mul");
STATISTIC(NumMulNUW, "Number of no-unsigned-wrap deductions for mul");
STATISTIC(NumShlNW, "Number of no-wrap deductions for shl");
STATISTIC(NumShlNSW, "Number of no-signed-wrap deductions for shl");
STATISTIC(NumShlNUW, "Number of no-unsigned-wrap deductions for shl");
STATISTIC(NumAbs, "Number of llvm.abs intrinsics removed");
STATISTIC(NumOverflows, "Number of overflow checks removed");
STATISTIC(NumSaturating,
"Number of saturating arithmetics converted to normal arithmetics");
STATISTIC(NumNonNull, "Number of function pointer arguments marked non-null");
STATISTIC(NumCmpIntr, "Number of llvm.[us]cmp intrinsics removed");
STATISTIC(NumMinMax, "Number of llvm.[us]{min,max} intrinsics removed");
STATISTIC(NumSMinMax,
"Number of llvm.s{min,max} intrinsics simplified to unsigned");
STATISTIC(NumUDivURemsNarrowedExpanded,
"Number of bound udiv's/urem's expanded");
STATISTIC(NumNNeg, "Number of zext/uitofp non-negative deductions");
static Constant *getConstantAt(Value *V, Instruction *At, LazyValueInfo *LVI) {
if (Constant *C = LVI->getConstant(V, At))
return C;
// TODO: The following really should be sunk inside LVI's core algorithm, or
// at least the outer shims around such.
auto *C = dyn_cast<CmpInst>(V);
if (!C)
return nullptr;
Value *Op0 = C->getOperand(0);
Constant *Op1 = dyn_cast<Constant>(C->getOperand(1));
if (!Op1)
return nullptr;
return LVI->getPredicateAt(C->getPredicate(), Op0, Op1, At,
/*UseBlockValue=*/false);
}
static bool processSelect(SelectInst *S, LazyValueInfo *LVI) {
if (S->getType()->isVectorTy() || isa<Constant>(S->getCondition()))
return false;
bool Changed = false;
for (Use &U : make_early_inc_range(S->uses())) {
auto *I = cast<Instruction>(U.getUser());
Constant *C;
if (auto *PN = dyn_cast<PHINode>(I))
C = LVI->getConstantOnEdge(S->getCondition(), PN->getIncomingBlock(U),
I->getParent(), I);
else
C = getConstantAt(S->getCondition(), I, LVI);
auto *CI = dyn_cast_or_null<ConstantInt>(C);
if (!CI)
continue;
U.set(CI->isOne() ? S->getTrueValue() : S->getFalseValue());
Changed = true;
++NumSelects;
}
if (Changed && S->use_empty())
S->eraseFromParent();
return Changed;
}
/// Try to simplify a phi with constant incoming values that match the edge
/// values of a non-constant value on all other edges:
/// bb0:
/// %isnull = icmp eq i8* %x, null
/// br i1 %isnull, label %bb2, label %bb1
/// bb1:
/// br label %bb2
/// bb2:
/// %r = phi i8* [ %x, %bb1 ], [ null, %bb0 ]
/// -->
/// %r = %x
static bool simplifyCommonValuePhi(PHINode *P, LazyValueInfo *LVI,
DominatorTree *DT) {
// Collect incoming constants and initialize possible common value.
SmallVector<std::pair<Constant *, unsigned>, 4> IncomingConstants;
Value *CommonValue = nullptr;
for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i) {
Value *Incoming = P->getIncomingValue(i);
if (auto *IncomingConstant = dyn_cast<Constant>(Incoming)) {
IncomingConstants.push_back(std::make_pair(IncomingConstant, i));
} else if (!CommonValue) {
// The potential common value is initialized to the first non-constant.
CommonValue = Incoming;
} else if (Incoming != CommonValue) {
// There can be only one non-constant common value.
return false;
}
}
if (!CommonValue || IncomingConstants.empty())
return false;
// The common value must be valid in all incoming blocks.
BasicBlock *ToBB = P->getParent();
if (auto *CommonInst = dyn_cast<Instruction>(CommonValue))
if (!DT->dominates(CommonInst, ToBB))
return false;
// We have a phi with exactly 1 variable incoming value and 1 or more constant
// incoming values. See if all constant incoming values can be mapped back to
// the same incoming variable value.
for (auto &IncomingConstant : IncomingConstants) {
Constant *C = IncomingConstant.first;
BasicBlock *IncomingBB = P->getIncomingBlock(IncomingConstant.second);
if (C != LVI->getConstantOnEdge(CommonValue, IncomingBB, ToBB, P))
return false;
}
// LVI only guarantees that the value matches a certain constant if the value
// is not poison. Make sure we don't replace a well-defined value with poison.
// This is usually satisfied due to a prior branch on the value.
if (!isGuaranteedNotToBePoison(CommonValue, nullptr, P, DT))
return false;
// All constant incoming values map to the same variable along the incoming
// edges of the phi. The phi is unnecessary.
P->replaceAllUsesWith(CommonValue);
P->eraseFromParent();
++NumPhiCommon;
return true;
}
static Value *getValueOnEdge(LazyValueInfo *LVI, Value *Incoming,
BasicBlock *From, BasicBlock *To,
Instruction *CxtI) {
if (Constant *C = LVI->getConstantOnEdge(Incoming, From, To, CxtI))
return C;
// Look if the incoming value is a select with a scalar condition for which
// LVI can tells us the value. In that case replace the incoming value with
// the appropriate value of the select. This often allows us to remove the
// select later.
auto *SI = dyn_cast<SelectInst>(Incoming);
if (!SI)
return nullptr;
// Once LVI learns to handle vector types, we could also add support
// for vector type constants that are not all zeroes or all ones.
Value *Condition = SI->getCondition();
if (!Condition->getType()->isVectorTy()) {
if (Constant *C = LVI->getConstantOnEdge(Condition, From, To, CxtI)) {
if (C->isOneValue())
return SI->getTrueValue();
if (C->isZeroValue())
return SI->getFalseValue();
}
}
// Look if the select has a constant but LVI tells us that the incoming
// value can never be that constant. In that case replace the incoming
// value with the other value of the select. This often allows us to
// remove the select later.
// The "false" case
if (auto *C = dyn_cast<Constant>(SI->getFalseValue()))
if (auto *Res = dyn_cast_or_null<ConstantInt>(
LVI->getPredicateOnEdge(ICmpInst::ICMP_EQ, SI, C, From, To, CxtI));
Res && Res->isZero())
return SI->getTrueValue();
// The "true" case,
// similar to the select "false" case, but try the select "true" value
if (auto *C = dyn_cast<Constant>(SI->getTrueValue()))
if (auto *Res = dyn_cast_or_null<ConstantInt>(
LVI->getPredicateOnEdge(ICmpInst::ICMP_EQ, SI, C, From, To, CxtI));
Res && Res->isZero())
return SI->getFalseValue();
return nullptr;
}
static bool processPHI(PHINode *P, LazyValueInfo *LVI, DominatorTree *DT,
const SimplifyQuery &SQ) {
bool Changed = false;
BasicBlock *BB = P->getParent();
for (unsigned i = 0, e = P->getNumIncomingValues(); i < e; ++i) {
Value *Incoming = P->getIncomingValue(i);
if (isa<Constant>(Incoming)) continue;
Value *V = getValueOnEdge(LVI, Incoming, P->getIncomingBlock(i), BB, P);
if (V) {
P->setIncomingValue(i, V);
Changed = true;
}
}
if (Value *V = simplifyInstruction(P, SQ)) {
P->replaceAllUsesWith(V);
P->eraseFromParent();
Changed = true;
}
if (!Changed)
Changed = simplifyCommonValuePhi(P, LVI, DT);
if (Changed)
++NumPhis;
return Changed;
}
static bool processICmp(ICmpInst *Cmp, LazyValueInfo *LVI) {
// Only for signed relational comparisons of integers.
if (!Cmp->getOperand(0)->getType()->isIntOrIntVectorTy())
return false;
if (!Cmp->isSigned() && (!Cmp->isUnsigned() || Cmp->hasSameSign()))
return false;
bool Changed = false;
ConstantRange CR1 = LVI->getConstantRangeAtUse(Cmp->getOperandUse(0),
/*UndefAllowed=*/false),
CR2 = LVI->getConstantRangeAtUse(Cmp->getOperandUse(1),
/*UndefAllowed=*/false);
if (Cmp->isSigned()) {
ICmpInst::Predicate UnsignedPred =
ConstantRange::getEquivalentPredWithFlippedSignedness(
Cmp->getPredicate(), CR1, CR2);
if (UnsignedPred == ICmpInst::Predicate::BAD_ICMP_PREDICATE)
return false;
++NumSICmps;
Cmp->setPredicate(UnsignedPred);
Changed = true;
}
if (ConstantRange::areInsensitiveToSignednessOfICmpPredicate(CR1, CR2)) {
Cmp->setSameSign();
Changed = true;
}
return Changed;
}
/// See if LazyValueInfo's ability to exploit edge conditions or range
/// information is sufficient to prove this comparison. Even for local
/// conditions, this can sometimes prove conditions instcombine can't by
/// exploiting range information.
static bool constantFoldCmp(CmpInst *Cmp, LazyValueInfo *LVI) {
Value *Op0 = Cmp->getOperand(0);
Value *Op1 = Cmp->getOperand(1);
Constant *Res = LVI->getPredicateAt(Cmp->getPredicate(), Op0, Op1, Cmp,
/*UseBlockValue=*/true);
if (!Res)
return false;
++NumCmps;
Cmp->replaceAllUsesWith(Res);
Cmp->eraseFromParent();
return true;
}
static bool processCmp(CmpInst *Cmp, LazyValueInfo *LVI) {
if (constantFoldCmp(Cmp, LVI))
return true;
if (auto *ICmp = dyn_cast<ICmpInst>(Cmp))
if (processICmp(ICmp, LVI))
return true;
return false;
}
/// Simplify a switch instruction by removing cases which can never fire. If the
/// uselessness of a case could be determined locally then constant propagation
/// would already have figured it out. Instead, walk the predecessors and
/// statically evaluate cases based on information available on that edge. Cases
/// that cannot fire no matter what the incoming edge can safely be removed. If
/// a case fires on every incoming edge then the entire switch can be removed
/// and replaced with a branch to the case destination.
static bool processSwitch(SwitchInst *I, LazyValueInfo *LVI,
DominatorTree *DT) {
DomTreeUpdater DTU(*DT, DomTreeUpdater::UpdateStrategy::Lazy);
Value *Cond = I->getCondition();
BasicBlock *BB = I->getParent();
// Analyse each switch case in turn.
bool Changed = false;
DenseMap<BasicBlock*, int> SuccessorsCount;
for (auto *Succ : successors(BB))
SuccessorsCount[Succ]++;
{ // Scope for SwitchInstProfUpdateWrapper. It must not live during
// ConstantFoldTerminator() as the underlying SwitchInst can be changed.
SwitchInstProfUpdateWrapper SI(*I);
ConstantRange CR =
LVI->getConstantRangeAtUse(I->getOperandUse(0), /*UndefAllowed=*/false);
unsigned ReachableCaseCount = 0;
for (auto CI = SI->case_begin(), CE = SI->case_end(); CI != CE;) {
ConstantInt *Case = CI->getCaseValue();
std::optional<bool> Predicate = std::nullopt;
if (!CR.contains(Case->getValue()))
Predicate = false;
else if (CR.isSingleElement() &&
*CR.getSingleElement() == Case->getValue())
Predicate = true;
if (!Predicate) {
// Handle missing cases, e.g., the range has a hole.
auto *Res = dyn_cast_or_null<ConstantInt>(
LVI->getPredicateAt(CmpInst::ICMP_EQ, Cond, Case, I,
/* UseBlockValue=*/true));
if (Res && Res->isZero())
Predicate = false;
else if (Res && Res->isOne())
Predicate = true;
}
if (Predicate && !*Predicate) {
// This case never fires - remove it.
BasicBlock *Succ = CI->getCaseSuccessor();
Succ->removePredecessor(BB);
CI = SI.removeCase(CI);
CE = SI->case_end();
// The condition can be modified by removePredecessor's PHI simplification
// logic.
Cond = SI->getCondition();
++NumDeadCases;
Changed = true;
if (--SuccessorsCount[Succ] == 0)
DTU.applyUpdatesPermissive({{DominatorTree::Delete, BB, Succ}});
continue;
}
if (Predicate && *Predicate) {
// This case always fires. Arrange for the switch to be turned into an
// unconditional branch by replacing the switch condition with the case
// value.
SI->setCondition(Case);
NumDeadCases += SI->getNumCases();
Changed = true;
break;
}
// Increment the case iterator since we didn't delete it.
++CI;
++ReachableCaseCount;
}
// The default dest is unreachable if all cases are covered.
if (!SI->defaultDestUndefined() &&
!CR.isSizeLargerThan(ReachableCaseCount)) {
BasicBlock *DefaultDest = SI->getDefaultDest();
BasicBlock *NewUnreachableBB =
BasicBlock::Create(BB->getContext(), "default.unreachable",
BB->getParent(), DefaultDest);
new UnreachableInst(BB->getContext(), NewUnreachableBB);
DefaultDest->removePredecessor(BB);
SI->setDefaultDest(NewUnreachableBB);
if (SuccessorsCount[DefaultDest] == 1)
DTU.applyUpdates({{DominatorTree::Delete, BB, DefaultDest}});
DTU.applyUpdates({{DominatorTree::Insert, BB, NewUnreachableBB}});
++NumDeadCases;
Changed = true;
}
}
if (Changed)
// If the switch has been simplified to the point where it can be replaced
// by a branch then do so now.
ConstantFoldTerminator(BB, /*DeleteDeadConditions = */ false,
/*TLI = */ nullptr, &DTU);
return Changed;
}
// See if we can prove that the given binary op intrinsic will not overflow.
static bool willNotOverflow(BinaryOpIntrinsic *BO, LazyValueInfo *LVI) {
ConstantRange LRange =
LVI->getConstantRangeAtUse(BO->getOperandUse(0), /*UndefAllowed*/ false);
ConstantRange RRange =
LVI->getConstantRangeAtUse(BO->getOperandUse(1), /*UndefAllowed*/ false);
ConstantRange NWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
BO->getBinaryOp(), RRange, BO->getNoWrapKind());
return NWRegion.contains(LRange);
}
static void setDeducedOverflowingFlags(Value *V, Instruction::BinaryOps Opcode,
bool NewNSW, bool NewNUW) {
Statistic *OpcNW, *OpcNSW, *OpcNUW;
switch (Opcode) {
case Instruction::Add:
OpcNW = &NumAddNW;
OpcNSW = &NumAddNSW;
OpcNUW = &NumAddNUW;
break;
case Instruction::Sub:
OpcNW = &NumSubNW;
OpcNSW = &NumSubNSW;
OpcNUW = &NumSubNUW;
break;
case Instruction::Mul:
OpcNW = &NumMulNW;
OpcNSW = &NumMulNSW;
OpcNUW = &NumMulNUW;
break;
case Instruction::Shl:
OpcNW = &NumShlNW;
OpcNSW = &NumShlNSW;
OpcNUW = &NumShlNUW;
break;
default:
llvm_unreachable("Will not be called with other binops");
}
auto *Inst = dyn_cast<Instruction>(V);
if (NewNSW) {
++NumNW;
++*OpcNW;
++NumNSW;
++*OpcNSW;
if (Inst)
Inst->setHasNoSignedWrap();
}
if (NewNUW) {
++NumNW;
++*OpcNW;
++NumNUW;
++*OpcNUW;
if (Inst)
Inst->setHasNoUnsignedWrap();
}
}
static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI);
// See if @llvm.abs argument is alays positive/negative, and simplify.
// Notably, INT_MIN can belong to either range, regardless of the NSW,
// because it is negation-invariant.
static bool processAbsIntrinsic(IntrinsicInst *II, LazyValueInfo *LVI) {
Value *X = II->getArgOperand(0);
bool IsIntMinPoison = cast<ConstantInt>(II->getArgOperand(1))->isOne();
APInt IntMin = APInt::getSignedMinValue(X->getType()->getScalarSizeInBits());
ConstantRange Range = LVI->getConstantRangeAtUse(
II->getOperandUse(0), /*UndefAllowed*/ IsIntMinPoison);
// Is X in [0, IntMin]? NOTE: INT_MIN is fine!
if (Range.icmp(CmpInst::ICMP_ULE, IntMin)) {
++NumAbs;
II->replaceAllUsesWith(X);
II->eraseFromParent();
return true;
}
// Is X in [IntMin, 0]? NOTE: INT_MIN is fine!
if (Range.getSignedMax().isNonPositive()) {
IRBuilder<> B(II);
Value *NegX = B.CreateNeg(X, II->getName(),
/*HasNSW=*/IsIntMinPoison);
++NumAbs;
II->replaceAllUsesWith(NegX);
II->eraseFromParent();
// See if we can infer some no-wrap flags.
if (auto *BO = dyn_cast<BinaryOperator>(NegX))
processBinOp(BO, LVI);
return true;
}
// Argument's range crosses zero.
// Can we at least tell that the argument is never INT_MIN?
if (!IsIntMinPoison && !Range.contains(IntMin)) {
++NumNSW;
++NumSubNSW;
II->setArgOperand(1, ConstantInt::getTrue(II->getContext()));
return true;
}
return false;
}
static bool processCmpIntrinsic(CmpIntrinsic *CI, LazyValueInfo *LVI) {
ConstantRange LHS_CR =
LVI->getConstantRangeAtUse(CI->getOperandUse(0), /*UndefAllowed*/ false);
ConstantRange RHS_CR =
LVI->getConstantRangeAtUse(CI->getOperandUse(1), /*UndefAllowed*/ false);
if (LHS_CR.icmp(CI->getGTPredicate(), RHS_CR)) {
++NumCmpIntr;
CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 1));
CI->eraseFromParent();
return true;
}
if (LHS_CR.icmp(CI->getLTPredicate(), RHS_CR)) {
++NumCmpIntr;
CI->replaceAllUsesWith(ConstantInt::getSigned(CI->getType(), -1));
CI->eraseFromParent();
return true;
}
if (LHS_CR.icmp(ICmpInst::ICMP_EQ, RHS_CR)) {
++NumCmpIntr;
CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 0));
CI->eraseFromParent();
return true;
}
return false;
}
// See if this min/max intrinsic always picks it's one specific operand.
// If not, check whether we can canonicalize signed minmax into unsigned version
static bool processMinMaxIntrinsic(MinMaxIntrinsic *MM, LazyValueInfo *LVI) {
CmpInst::Predicate Pred = CmpInst::getNonStrictPredicate(MM->getPredicate());
ConstantRange LHS_CR = LVI->getConstantRangeAtUse(MM->getOperandUse(0),
/*UndefAllowed*/ false);
ConstantRange RHS_CR = LVI->getConstantRangeAtUse(MM->getOperandUse(1),
/*UndefAllowed*/ false);
if (LHS_CR.icmp(Pred, RHS_CR)) {
++NumMinMax;
MM->replaceAllUsesWith(MM->getLHS());
MM->eraseFromParent();
return true;
}
if (RHS_CR.icmp(Pred, LHS_CR)) {
++NumMinMax;
MM->replaceAllUsesWith(MM->getRHS());
MM->eraseFromParent();
return true;
}
if (MM->isSigned() &&
ConstantRange::areInsensitiveToSignednessOfICmpPredicate(LHS_CR,
RHS_CR)) {
++NumSMinMax;
IRBuilder<> B(MM);
MM->replaceAllUsesWith(B.CreateBinaryIntrinsic(
MM->getIntrinsicID() == Intrinsic::smin ? Intrinsic::umin
: Intrinsic::umax,
MM->getLHS(), MM->getRHS()));
MM->eraseFromParent();
return true;
}
return false;
}
// Rewrite this with.overflow intrinsic as non-overflowing.
static bool processOverflowIntrinsic(WithOverflowInst *WO, LazyValueInfo *LVI) {
IRBuilder<> B(WO);
Instruction::BinaryOps Opcode = WO->getBinaryOp();
bool NSW = WO->isSigned();
bool NUW = !WO->isSigned();
Value *NewOp =
B.CreateBinOp(Opcode, WO->getLHS(), WO->getRHS(), WO->getName());
setDeducedOverflowingFlags(NewOp, Opcode, NSW, NUW);
StructType *ST = cast<StructType>(WO->getType());
Constant *Struct = ConstantStruct::get(ST,
{ PoisonValue::get(ST->getElementType(0)),
ConstantInt::getFalse(ST->getElementType(1)) });
Value *NewI = B.CreateInsertValue(Struct, NewOp, 0);
WO->replaceAllUsesWith(NewI);
WO->eraseFromParent();
++NumOverflows;
// See if we can infer the other no-wrap too.
if (auto *BO = dyn_cast<BinaryOperator>(NewOp))
processBinOp(BO, LVI);
return true;
}
static bool processSaturatingInst(SaturatingInst *SI, LazyValueInfo *LVI) {
Instruction::BinaryOps Opcode = SI->getBinaryOp();
bool NSW = SI->isSigned();
bool NUW = !SI->isSigned();
BinaryOperator *BinOp = BinaryOperator::Create(
Opcode, SI->getLHS(), SI->getRHS(), SI->getName(), SI->getIterator());
BinOp->setDebugLoc(SI->getDebugLoc());
setDeducedOverflowingFlags(BinOp, Opcode, NSW, NUW);
SI->replaceAllUsesWith(BinOp);
SI->eraseFromParent();
++NumSaturating;
// See if we can infer the other no-wrap too.
if (auto *BO = dyn_cast<BinaryOperator>(BinOp))
processBinOp(BO, LVI);
return true;
}
/// Infer nonnull attributes for the arguments at the specified callsite.
static bool processCallSite(CallBase &CB, LazyValueInfo *LVI) {
if (CB.getIntrinsicID() == Intrinsic::abs) {
return processAbsIntrinsic(&cast<IntrinsicInst>(CB), LVI);
}
if (auto *CI = dyn_cast<CmpIntrinsic>(&CB)) {
return processCmpIntrinsic(CI, LVI);
}
if (auto *MM = dyn_cast<MinMaxIntrinsic>(&CB)) {
return processMinMaxIntrinsic(MM, LVI);
}
if (auto *WO = dyn_cast<WithOverflowInst>(&CB)) {
if (willNotOverflow(WO, LVI))
return processOverflowIntrinsic(WO, LVI);
}
if (auto *SI = dyn_cast<SaturatingInst>(&CB)) {
if (willNotOverflow(SI, LVI))
return processSaturatingInst(SI, LVI);
}
bool Changed = false;
// Deopt bundle operands are intended to capture state with minimal
// perturbance of the code otherwise. If we can find a constant value for
// any such operand and remove a use of the original value, that's
// desireable since it may allow further optimization of that value (e.g. via
// single use rules in instcombine). Since deopt uses tend to,
// idiomatically, appear along rare conditional paths, it's reasonable likely
// we may have a conditional fact with which LVI can fold.
if (auto DeoptBundle = CB.getOperandBundle(LLVMContext::OB_deopt)) {
for (const Use &ConstU : DeoptBundle->Inputs) {
Use &U = const_cast<Use&>(ConstU);
Value *V = U.get();
if (V->getType()->isVectorTy()) continue;
if (isa<Constant>(V)) continue;
Constant *C = LVI->getConstant(V, &CB);
if (!C) continue;
U.set(C);
Changed = true;
}
}
SmallVector<unsigned, 4> ArgNos;
unsigned ArgNo = 0;
for (Value *V : CB.args()) {
PointerType *Type = dyn_cast<PointerType>(V->getType());
// Try to mark pointer typed parameters as non-null. We skip the
// relatively expensive analysis for constants which are obviously either
// null or non-null to start with.
if (Type && !CB.paramHasAttr(ArgNo, Attribute::NonNull) &&
!isa<Constant>(V))
if (auto *Res = dyn_cast_or_null<ConstantInt>(LVI->getPredicateAt(
ICmpInst::ICMP_EQ, V, ConstantPointerNull::get(Type), &CB,
/*UseBlockValue=*/false));
Res && Res->isZero())
ArgNos.push_back(ArgNo);
ArgNo++;
}
assert(ArgNo == CB.arg_size() && "Call arguments not processed correctly.");
if (ArgNos.empty())
return Changed;
NumNonNull += ArgNos.size();
AttributeList AS = CB.getAttributes();
LLVMContext &Ctx = CB.getContext();
AS = AS.addParamAttribute(Ctx, ArgNos,
Attribute::get(Ctx, Attribute::NonNull));
CB.setAttributes(AS);
return true;
}
enum class Domain { NonNegative, NonPositive, Unknown };
static Domain getDomain(const ConstantRange &CR) {
if (CR.isAllNonNegative())
return Domain::NonNegative;
if (CR.icmp(ICmpInst::ICMP_SLE, APInt::getZero(CR.getBitWidth())))
return Domain::NonPositive;
return Domain::Unknown;
}
/// Try to shrink a sdiv/srem's width down to the smallest power of two that's
/// sufficient to contain its operands.
static bool narrowSDivOrSRem(BinaryOperator *Instr, const ConstantRange &LCR,
const ConstantRange &RCR) {
assert(Instr->getOpcode() == Instruction::SDiv ||
Instr->getOpcode() == Instruction::SRem);
// Find the smallest power of two bitwidth that's sufficient to hold Instr's
// operands.
unsigned OrigWidth = Instr->getType()->getScalarSizeInBits();
// What is the smallest bit width that can accommodate the entire value ranges
// of both of the operands?
unsigned MinSignedBits =
std::max(LCR.getMinSignedBits(), RCR.getMinSignedBits());
// sdiv/srem is UB if divisor is -1 and divident is INT_MIN, so unless we can
// prove that such a combination is impossible, we need to bump the bitwidth.
if (RCR.contains(APInt::getAllOnes(OrigWidth)) &&
LCR.contains(APInt::getSignedMinValue(MinSignedBits).sext(OrigWidth)))
++MinSignedBits;
// Don't shrink below 8 bits wide.
unsigned NewWidth = std::max<unsigned>(PowerOf2Ceil(MinSignedBits), 8);
// NewWidth might be greater than OrigWidth if OrigWidth is not a power of
// two.
if (NewWidth >= OrigWidth)
return false;
++NumSDivSRemsNarrowed;
IRBuilder<> B{Instr};
auto *TruncTy = Instr->getType()->getWithNewBitWidth(NewWidth);
auto *LHS = B.CreateTruncOrBitCast(Instr->getOperand(0), TruncTy,
Instr->getName() + ".lhs.trunc");
auto *RHS = B.CreateTruncOrBitCast(Instr->getOperand(1), TruncTy,
Instr->getName() + ".rhs.trunc");
auto *BO = B.CreateBinOp(Instr->getOpcode(), LHS, RHS, Instr->getName());
auto *Sext = B.CreateSExt(BO, Instr->getType(), Instr->getName() + ".sext");
if (auto *BinOp = dyn_cast<BinaryOperator>(BO))
if (BinOp->getOpcode() == Instruction::SDiv)
BinOp->setIsExact(Instr->isExact());
Instr->replaceAllUsesWith(Sext);
Instr->eraseFromParent();
return true;
}
static bool expandUDivOrURem(BinaryOperator *Instr, const ConstantRange &XCR,
const ConstantRange &YCR) {
Type *Ty = Instr->getType();
assert(Instr->getOpcode() == Instruction::UDiv ||
Instr->getOpcode() == Instruction::URem);
bool IsRem = Instr->getOpcode() == Instruction::URem;
Value *X = Instr->getOperand(0);
Value *Y = Instr->getOperand(1);
// X u/ Y -> 0 iff X u< Y
// X u% Y -> X iff X u< Y
if (XCR.icmp(ICmpInst::ICMP_ULT, YCR)) {
Instr->replaceAllUsesWith(IsRem ? X : Constant::getNullValue(Ty));
Instr->eraseFromParent();
++NumUDivURemsNarrowedExpanded;
return true;
}
// Given
// R = X u% Y
// We can represent the modulo operation as a loop/self-recursion:
// urem_rec(X, Y):
// Z = X - Y
// if X u< Y
// ret X
// else
// ret urem_rec(Z, Y)
// which isn't better, but if we only need a single iteration
// to compute the answer, this becomes quite good:
// R = X < Y ? X : X - Y iff X u< 2*Y (w/ unsigned saturation)
// Now, we do not care about all full multiples of Y in X, they do not change
// the answer, thus we could rewrite the expression as:
// X* = X - (Y * |_ X / Y _|)
// R = X* % Y
// so we don't need the *first* iteration to return, we just need to
// know *which* iteration will always return, so we could also rewrite it as:
// X* = X - (Y * |_ X / Y _|)
// R = X* % Y iff X* u< 2*Y (w/ unsigned saturation)
// but that does not seem profitable here.
// Even if we don't know X's range, the divisor may be so large, X can't ever
// be 2x larger than that. I.e. if divisor is always negative.
if (!XCR.icmp(ICmpInst::ICMP_ULT, YCR.uadd_sat(YCR)) && !YCR.isAllNegative())
return false;
IRBuilder<> B(Instr);
Value *ExpandedOp;
if (XCR.icmp(ICmpInst::ICMP_UGE, YCR)) {
// If X is between Y and 2*Y the result is known.
if (IsRem)
ExpandedOp = B.CreateNUWSub(X, Y);
else
ExpandedOp = ConstantInt::get(Instr->getType(), 1);
} else if (IsRem) {
// NOTE: this transformation introduces two uses of X,
// but it may be undef so we must freeze it first.
Value *FrozenX = X;
if (!isGuaranteedNotToBeUndef(X))
FrozenX = B.CreateFreeze(X, X->getName() + ".frozen");
Value *FrozenY = Y;
if (!isGuaranteedNotToBeUndef(Y))
FrozenY = B.CreateFreeze(Y, Y->getName() + ".frozen");
auto *AdjX = B.CreateNUWSub(FrozenX, FrozenY, Instr->getName() + ".urem");
auto *Cmp = B.CreateICmp(ICmpInst::ICMP_ULT, FrozenX, FrozenY,
Instr->getName() + ".cmp");
ExpandedOp = B.CreateSelect(Cmp, FrozenX, AdjX);
} else {
auto *Cmp =
B.CreateICmp(ICmpInst::ICMP_UGE, X, Y, Instr->getName() + ".cmp");
ExpandedOp = B.CreateZExt(Cmp, Ty, Instr->getName() + ".udiv");
}
ExpandedOp->takeName(Instr);
Instr->replaceAllUsesWith(ExpandedOp);
Instr->eraseFromParent();
++NumUDivURemsNarrowedExpanded;
return true;
}
/// Try to shrink a udiv/urem's width down to the smallest power of two that's
/// sufficient to contain its operands.
static bool narrowUDivOrURem(BinaryOperator *Instr, const ConstantRange &XCR,
const ConstantRange &YCR) {
assert(Instr->getOpcode() == Instruction::UDiv ||
Instr->getOpcode() == Instruction::URem);
// Find the smallest power of two bitwidth that's sufficient to hold Instr's
// operands.
// What is the smallest bit width that can accommodate the entire value ranges
// of both of the operands?
unsigned MaxActiveBits = std::max(XCR.getActiveBits(), YCR.getActiveBits());
// Don't shrink below 8 bits wide.
unsigned NewWidth = std::max<unsigned>(PowerOf2Ceil(MaxActiveBits), 8);
// NewWidth might be greater than OrigWidth if OrigWidth is not a power of
// two.
if (NewWidth >= Instr->getType()->getScalarSizeInBits())
return false;
++NumUDivURemsNarrowed;
IRBuilder<> B{Instr};
auto *TruncTy = Instr->getType()->getWithNewBitWidth(NewWidth);
auto *LHS = B.CreateTruncOrBitCast(Instr->getOperand(0), TruncTy,
Instr->getName() + ".lhs.trunc");
auto *RHS = B.CreateTruncOrBitCast(Instr->getOperand(1), TruncTy,
Instr->getName() + ".rhs.trunc");
auto *BO = B.CreateBinOp(Instr->getOpcode(), LHS, RHS, Instr->getName());
auto *Zext = B.CreateZExt(BO, Instr->getType(), Instr->getName() + ".zext");
if (auto *BinOp = dyn_cast<BinaryOperator>(BO))
if (BinOp->getOpcode() == Instruction::UDiv)
BinOp->setIsExact(Instr->isExact());
Instr->replaceAllUsesWith(Zext);
Instr->eraseFromParent();
return true;
}
static bool processUDivOrURem(BinaryOperator *Instr, LazyValueInfo *LVI) {
assert(Instr->getOpcode() == Instruction::UDiv ||
Instr->getOpcode() == Instruction::URem);
ConstantRange XCR = LVI->getConstantRangeAtUse(Instr->getOperandUse(0),
/*UndefAllowed*/ false);
// Allow undef for RHS, as we can assume it is division by zero UB.
ConstantRange YCR = LVI->getConstantRangeAtUse(Instr->getOperandUse(1),
/*UndefAllowed*/ true);
if (expandUDivOrURem(Instr, XCR, YCR))
return true;
return narrowUDivOrURem(Instr, XCR, YCR);
}
static bool processSRem(BinaryOperator *SDI, const ConstantRange &LCR,
const ConstantRange &RCR, LazyValueInfo *LVI) {
assert(SDI->getOpcode() == Instruction::SRem);
if (LCR.abs().icmp(CmpInst::ICMP_ULT, RCR.abs())) {
SDI->replaceAllUsesWith(SDI->getOperand(0));
SDI->eraseFromParent();
return true;
}
struct Operand {
Value *V;
Domain D;
};
std::array<Operand, 2> Ops = {{{SDI->getOperand(0), getDomain(LCR)},
{SDI->getOperand(1), getDomain(RCR)}}};
if (Ops[0].D == Domain::Unknown || Ops[1].D == Domain::Unknown)
return false;
// We know domains of both of the operands!
++NumSRems;
// We need operands to be non-negative, so negate each one that isn't.
for (Operand &Op : Ops) {
if (Op.D == Domain::NonNegative)
continue;
auto *BO = BinaryOperator::CreateNeg(Op.V, Op.V->getName() + ".nonneg",
SDI->getIterator());
BO->setDebugLoc(SDI->getDebugLoc());
Op.V = BO;
}
auto *URem = BinaryOperator::CreateURem(Ops[0].V, Ops[1].V, SDI->getName(),
SDI->getIterator());
URem->setDebugLoc(SDI->getDebugLoc());
auto *Res = URem;
// If the divident was non-positive, we need to negate the result.
if (Ops[0].D == Domain::NonPositive) {
Res = BinaryOperator::CreateNeg(Res, Res->getName() + ".neg",
SDI->getIterator());
Res->setDebugLoc(SDI->getDebugLoc());
}
SDI->replaceAllUsesWith(Res);
SDI->eraseFromParent();
// Try to simplify our new urem.
processUDivOrURem(URem, LVI);
return true;
}
/// See if LazyValueInfo's ability to exploit edge conditions or range
/// information is sufficient to prove the signs of both operands of this SDiv.
/// If this is the case, replace the SDiv with a UDiv. Even for local
/// conditions, this can sometimes prove conditions instcombine can't by
/// exploiting range information.
static bool processSDiv(BinaryOperator *SDI, const ConstantRange &LCR,
const ConstantRange &RCR, LazyValueInfo *LVI) {
assert(SDI->getOpcode() == Instruction::SDiv);
// Check whether the division folds to a constant.
ConstantRange DivCR = LCR.sdiv(RCR);
if (const APInt *Elem = DivCR.getSingleElement()) {
SDI->replaceAllUsesWith(ConstantInt::get(SDI->getType(), *Elem));
SDI->eraseFromParent();
return true;
}
struct Operand {
Value *V;
Domain D;
};
std::array<Operand, 2> Ops = {{{SDI->getOperand(0), getDomain(LCR)},
{SDI->getOperand(1), getDomain(RCR)}}};
if (Ops[0].D == Domain::Unknown || Ops[1].D == Domain::Unknown)
return false;
// We know domains of both of the operands!
++NumSDivs;
// We need operands to be non-negative, so negate each one that isn't.
for (Operand &Op : Ops) {
if (Op.D == Domain::NonNegative)
continue;
auto *BO = BinaryOperator::CreateNeg(Op.V, Op.V->getName() + ".nonneg",
SDI->getIterator());
BO->setDebugLoc(SDI->getDebugLoc());
Op.V = BO;
}
auto *UDiv = BinaryOperator::CreateUDiv(Ops[0].V, Ops[1].V, SDI->getName(),
SDI->getIterator());
UDiv->setDebugLoc(SDI->getDebugLoc());
UDiv->setIsExact(SDI->isExact());
auto *Res = UDiv;
// If the operands had two different domains, we need to negate the result.
if (Ops[0].D != Ops[1].D) {
Res = BinaryOperator::CreateNeg(Res, Res->getName() + ".neg",
SDI->getIterator());
Res->setDebugLoc(SDI->getDebugLoc());
}
SDI->replaceAllUsesWith(Res);
SDI->eraseFromParent();
// Try to simplify our new udiv.
processUDivOrURem(UDiv, LVI);
return true;
}
static bool processSDivOrSRem(BinaryOperator *Instr, LazyValueInfo *LVI) {
assert(Instr->getOpcode() == Instruction::SDiv ||
Instr->getOpcode() == Instruction::SRem);
ConstantRange LCR =
LVI->getConstantRangeAtUse(Instr->getOperandUse(0), /*AllowUndef*/ false);
// Allow undef for RHS, as we can assume it is division by zero UB.
ConstantRange RCR =
LVI->getConstantRangeAtUse(Instr->getOperandUse(1), /*AlloweUndef*/ true);
if (Instr->getOpcode() == Instruction::SDiv)
if (processSDiv(Instr, LCR, RCR, LVI))
return true;
if (Instr->getOpcode() == Instruction::SRem) {
if (processSRem(Instr, LCR, RCR, LVI))
return true;
}
return narrowSDivOrSRem(Instr, LCR, RCR);
}
static bool processAShr(BinaryOperator *SDI, LazyValueInfo *LVI) {
ConstantRange LRange =
LVI->getConstantRangeAtUse(SDI->getOperandUse(0), /*UndefAllowed*/ false);
unsigned OrigWidth = SDI->getType()->getScalarSizeInBits();
ConstantRange NegOneOrZero =
ConstantRange(APInt(OrigWidth, (uint64_t)-1, true), APInt(OrigWidth, 1));
if (NegOneOrZero.contains(LRange)) {
// ashr of -1 or 0 never changes the value, so drop the whole instruction
++NumAShrsRemoved;
SDI->replaceAllUsesWith(SDI->getOperand(0));
SDI->eraseFromParent();
return true;
}
if (!LRange.isAllNonNegative())
return false;
++NumAShrsConverted;
auto *BO = BinaryOperator::CreateLShr(SDI->getOperand(0), SDI->getOperand(1),
"", SDI->getIterator());
BO->takeName(SDI);
BO->setDebugLoc(SDI->getDebugLoc());
BO->setIsExact(SDI->isExact());
SDI->replaceAllUsesWith(BO);
SDI->eraseFromParent();
return true;
}
static bool processSExt(SExtInst *SDI, LazyValueInfo *LVI) {
const Use &Base = SDI->getOperandUse(0);
if (!LVI->getConstantRangeAtUse(Base, /*UndefAllowed*/ false)
.isAllNonNegative())
return false;
++NumSExt;
auto *ZExt = CastInst::CreateZExtOrBitCast(Base, SDI->getType(), "",
SDI->getIterator());
ZExt->takeName(SDI);
ZExt->setDebugLoc(SDI->getDebugLoc());
ZExt->setNonNeg();
SDI->replaceAllUsesWith(ZExt);
SDI->eraseFromParent();
return true;
}
static bool processPossibleNonNeg(PossiblyNonNegInst *I, LazyValueInfo *LVI) {
if (I->hasNonNeg())
return false;
const Use &Base = I->getOperandUse(0);
if (!LVI->getConstantRangeAtUse(Base, /*UndefAllowed*/ false)
.isAllNonNegative())
return false;
++NumNNeg;
I->setNonNeg();
return true;
}
static bool processZExt(ZExtInst *ZExt, LazyValueInfo *LVI) {
return processPossibleNonNeg(cast<PossiblyNonNegInst>(ZExt), LVI);
}
static bool processUIToFP(UIToFPInst *UIToFP, LazyValueInfo *LVI) {
return processPossibleNonNeg(cast<PossiblyNonNegInst>(UIToFP), LVI);
}
static bool processSIToFP(SIToFPInst *SIToFP, LazyValueInfo *LVI) {
const Use &Base = SIToFP->getOperandUse(0);
if (!LVI->getConstantRangeAtUse(Base, /*UndefAllowed*/ false)
.isAllNonNegative())
return false;
++NumSIToFP;
auto *UIToFP = CastInst::Create(Instruction::UIToFP, Base, SIToFP->getType(),
"", SIToFP->getIterator());
UIToFP->takeName(SIToFP);
UIToFP->setDebugLoc(SIToFP->getDebugLoc());
UIToFP->setNonNeg();
SIToFP->replaceAllUsesWith(UIToFP);
SIToFP->eraseFromParent();
return true;
}
static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI) {
using OBO = OverflowingBinaryOperator;
bool NSW = BinOp->hasNoSignedWrap();
bool NUW = BinOp->hasNoUnsignedWrap();
if (NSW && NUW)
return false;
Instruction::BinaryOps Opcode = BinOp->getOpcode();
ConstantRange LRange = LVI->getConstantRangeAtUse(BinOp->getOperandUse(0),
/*UndefAllowed=*/false);
ConstantRange RRange = LVI->getConstantRangeAtUse(BinOp->getOperandUse(1),
/*UndefAllowed=*/false);
bool Changed = false;
bool NewNUW = false, NewNSW = false;
if (!NUW) {
ConstantRange NUWRange = ConstantRange::makeGuaranteedNoWrapRegion(
Opcode, RRange, OBO::NoUnsignedWrap);
NewNUW = NUWRange.contains(LRange);
Changed |= NewNUW;
}
if (!NSW) {
ConstantRange NSWRange = ConstantRange::makeGuaranteedNoWrapRegion(
Opcode, RRange, OBO::NoSignedWrap);
NewNSW = NSWRange.contains(LRange);
Changed |= NewNSW;
}
setDeducedOverflowingFlags(BinOp, Opcode, NewNSW, NewNUW);
return Changed;
}
static bool processAnd(BinaryOperator *BinOp, LazyValueInfo *LVI) {
using namespace llvm::PatternMatch;
// Pattern match (and lhs, C) where C includes a superset of bits which might
// be set in lhs. This is a common truncation idiom created by instcombine.
const Use &LHS = BinOp->getOperandUse(0);
const APInt *RHS;
if (!match(BinOp->getOperand(1), m_LowBitMask(RHS)))
return false;
// We can only replace the AND with LHS based on range info if the range does
// not include undef.
ConstantRange LRange =
LVI->getConstantRangeAtUse(LHS, /*UndefAllowed=*/false);
if (!LRange.getUnsignedMax().ule(*RHS))
return false;
BinOp->replaceAllUsesWith(LHS);
BinOp->eraseFromParent();
NumAnd++;
return true;
}
static bool runImpl(Function &F, LazyValueInfo *LVI, DominatorTree *DT,
const SimplifyQuery &SQ) {
bool FnChanged = false;
std::optional<ConstantRange> RetRange;
if (F.hasExactDefinition() && F.getReturnType()->isIntOrIntVectorTy())
RetRange =
ConstantRange::getEmpty(F.getReturnType()->getScalarSizeInBits());
// Visiting in a pre-order depth-first traversal causes us to simplify early
// blocks before querying later blocks (which require us to analyze early
// blocks). Eagerly simplifying shallow blocks means there is strictly less
// work to do for deep blocks. This also means we don't visit unreachable
// blocks.
for (BasicBlock *BB : depth_first(&F.getEntryBlock())) {
bool BBChanged = false;
for (Instruction &II : llvm::make_early_inc_range(*BB)) {
switch (II.getOpcode()) {
case Instruction::Select:
BBChanged |= processSelect(cast<SelectInst>(&II), LVI);
break;
case Instruction::PHI:
BBChanged |= processPHI(cast<PHINode>(&II), LVI, DT, SQ);
break;
case Instruction::ICmp:
case Instruction::FCmp:
BBChanged |= processCmp(cast<CmpInst>(&II), LVI);
break;
case Instruction::Call:
case Instruction::Invoke:
BBChanged |= processCallSite(cast<CallBase>(II), LVI);
break;
case Instruction::SRem:
case Instruction::SDiv:
BBChanged |= processSDivOrSRem(cast<BinaryOperator>(&II), LVI);
break;
case Instruction::UDiv:
case Instruction::URem:
BBChanged |= processUDivOrURem(cast<BinaryOperator>(&II), LVI);
break;
case Instruction::AShr:
BBChanged |= processAShr(cast<BinaryOperator>(&II), LVI);
break;
case Instruction::SExt:
BBChanged |= processSExt(cast<SExtInst>(&II), LVI);
break;
case Instruction::ZExt:
BBChanged |= processZExt(cast<ZExtInst>(&II), LVI);
break;
case Instruction::UIToFP:
BBChanged |= processUIToFP(cast<UIToFPInst>(&II), LVI);
break;
case Instruction::SIToFP:
BBChanged |= processSIToFP(cast<SIToFPInst>(&II), LVI);
break;
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
case Instruction::Shl:
BBChanged |= processBinOp(cast<BinaryOperator>(&II), LVI);
break;
case Instruction::And:
BBChanged |= processAnd(cast<BinaryOperator>(&II), LVI);
break;
}
}
Instruction *Term = BB->getTerminator();
switch (Term->getOpcode()) {
case Instruction::Switch:
BBChanged |= processSwitch(cast<SwitchInst>(Term), LVI, DT);
break;
case Instruction::Ret: {
auto *RI = cast<ReturnInst>(Term);
// Try to determine the return value if we can. This is mainly here to
// simplify the writing of unit tests, but also helps to enable IPO by
// constant folding the return values of callees.
auto *RetVal = RI->getReturnValue();
if (!RetVal) break; // handle "ret void"
if (RetRange && !RetRange->isFullSet())
RetRange =
RetRange->unionWith(LVI->getConstantRange(RetVal, RI,
/*UndefAllowed=*/false));
if (isa<Constant>(RetVal)) break; // nothing to do
if (auto *C = getConstantAt(RetVal, RI, LVI)) {
++NumReturns;
RI->replaceUsesOfWith(RetVal, C);
BBChanged = true;
}
}
}
FnChanged |= BBChanged;
}
// Infer range attribute on return value.
if (RetRange && !RetRange->isFullSet()) {
Attribute RangeAttr = F.getRetAttribute(Attribute::Range);
if (RangeAttr.isValid())
RetRange = RetRange->intersectWith(RangeAttr.getRange());
// Don't add attribute for constant integer returns to reduce noise. These
// are propagated across functions by IPSCCP.
if (!RetRange->isEmptySet() && !RetRange->isSingleElement()) {
F.addRangeRetAttr(*RetRange);
FnChanged = true;
}
}
return FnChanged;
}
PreservedAnalyses
CorrelatedValuePropagationPass::run(Function &F, FunctionAnalysisManager &AM) {
LazyValueInfo *LVI = &AM.getResult<LazyValueAnalysis>(F);
DominatorTree *DT = &AM.getResult<DominatorTreeAnalysis>(F);
bool Changed = runImpl(F, LVI, DT, getBestSimplifyQuery(AM, F));
PreservedAnalyses PA;
if (!Changed) {
PA = PreservedAnalyses::all();
} else {
#if defined(EXPENSIVE_CHECKS)
assert(DT->verify(DominatorTree::VerificationLevel::Full));
#else
assert(DT->verify(DominatorTree::VerificationLevel::Fast));
#endif // EXPENSIVE_CHECKS
PA.preserve<DominatorTreeAnalysis>();
PA.preserve<LazyValueAnalysis>();
}
// Keeping LVI alive is expensive, both because it uses a lot of memory, and
// because invalidating values in LVI is expensive. While CVP does preserve
// LVI, we know that passes after JumpThreading+CVP will not need the result
// of this analysis, so we forcefully discard it early.
PA.abandon<LazyValueAnalysis>();
return PA;
}
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