mirror of
https://github.com/revng/revng
synced 2026-06-21 14:07:57 +00:00
TANP: Move constants to right side of comparisons
Implements transforms when the results of sub or add with a constant operand are compared against constant: 1) x + a == b --> x == b - a 2) x + a != b --> x != b - a 3) x + a <= b --> x <= b - a 4) x + a < b --> x < b - a 5) x + a >= b --> x >= b - a 6) x + a > b --> x > b - a After the transformation, the right hand side is also enqued for analysis to detect opporunities to use unary minus if a-b is a negative constant.
This commit is contained in:
Valentina Sona
committed by
Pietro Fezzardi
Pietro Fezzardi
parent
74df82e0ca
commit
0e61bf3fd2
@@ -2,7 +2,9 @@
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// Copyright rev.ng Labs Srl. See LICENSE.md for details.
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//
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/MDBuilder.h"
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#include "llvm/IR/PatternMatch.h"
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@@ -28,115 +30,258 @@ public:
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using TANP = TwosComplementArithmeticNormalizationPass;
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class UnaryMinusBuilder {
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OpaqueFunctionsPool<llvm::Type *> Pool;
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llvm::IRBuilder<> Builder;
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public:
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UnaryMinusBuilder(llvm::Function &F) :
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Pool(F.getParent(), false), Builder(F.getContext()) {
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initUnaryMinusPool(Pool);
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}
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void SetInsertPoint(llvm::Instruction *I) { Builder.SetInsertPoint(I); }
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llvm::CallInst *operator()(llvm::Type *IntType, llvm::APInt Value) {
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revng_assert(llvm::isa<llvm::IntegerType>(IntType));
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llvm::Function *Func = Pool.get(IntType, IntType, IntType, "unary_minus");
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auto ConstInt = llvm::ConstantInt::getSigned(IntType,
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Value.abs().getLimitedValue());
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return Builder.CreateCall(Func, { ConstInt });
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}
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};
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class BinaryNotBuilder {
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OpaqueFunctionsPool<llvm::Type *> Pool;
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llvm::IRBuilder<> Builder;
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public:
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BinaryNotBuilder(llvm::Function &F) :
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Pool(F.getParent(), false), Builder(F.getContext()) {
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initBinaryNotPool(Pool);
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}
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void SetInsertPoint(llvm::Instruction *I) { Builder.SetInsertPoint(I); }
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llvm::CallInst *operator()(llvm::Type *IntType, llvm::Value *Val) {
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revng_assert(isa<llvm::IntegerType>(IntType));
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llvm::Function *Func = Pool.get(IntType, IntType, IntType, "binary_not");
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return Builder.CreateCall(Func, { Val });
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}
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};
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static bool isSignedComparison(llvm::ICmpInst::Predicate P) {
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return P == llvm::ICmpInst::Predicate::ICMP_SGE
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or P == llvm::ICmpInst::Predicate::ICMP_SGT
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or P == llvm::ICmpInst::Predicate::ICMP_SLE
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or P == llvm::ICmpInst::Predicate::ICMP_SLT;
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}
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static bool isEqualityComparison(llvm::ICmpInst::Predicate P) {
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return P == llvm::ICmpInst::Predicate::ICMP_EQ
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or P == llvm::ICmpInst::Predicate::ICMP_NE;
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}
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bool TANP::runOnFunction(llvm::Function &F) {
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using namespace llvm;
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using namespace PatternMatch;
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IRBuilder<> Builder(F.getContext());
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UnaryMinusBuilder BuildUnaryMinus{ F };
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BinaryNotBuilder BuildBinaryNot{ F };
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llvm::IRBuilder<> Builder{ F.getContext() };
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OpaqueFunctionsPool<llvm::Type *> UnaryMinusPool(F.getParent(), false);
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initUnaryMinusPool(UnaryMinusPool);
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OpaqueFunctionsPool<llvm::Type *> BinaryNotPool(F.getParent(), false);
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initBinaryNotPool(BinaryNotPool);
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auto BuildUnaryMinus =
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[&Builder, &UnaryMinusPool](const Value *Val, const APInt *Int) -> Value * {
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const auto IntType = Val->getType();
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auto Func = UnaryMinusPool.get(IntType, IntType, IntType, "unary_minus");
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auto IntValue = Int->abs().getLimitedValue();
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auto Value = ConstantInt::getSigned(IntType, IntValue);
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auto Call = Builder.CreateCall(Func, { Value });
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return Call;
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};
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bool Changed = false;
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SmallVector<Instruction *, 8> DeadInsts;
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for (BasicBlock &BB : F) {
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for (Instruction &I : BB) {
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Value *Val = nullptr;
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const APInt *Int = nullptr;
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Value *NewV = nullptr;
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ICmpInst::Predicate Pred;
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Builder.SetInsertPoint(&I);
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if (match(&I, m_Add(m_Value(Val), m_APInt(Int))) && Int->isNegative()) {
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Value *NewV = nullptr;
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if ((match(&I, m_Xor(m_Value(Val), m_APInt(Int)))
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or match(&I, m_Xor(m_APInt(Int), m_Value(Val))))
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and Int->isAllOnesValue()) {
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BuildBinaryNot.SetInsertPoint(&I);
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NewV = BuildBinaryNot(I.getType(), Val);
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} else if (match(&I, m_Add(m_Value(Val), m_APInt(Int)))
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and Int->isNegative()) {
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Builder.SetInsertPoint(&I);
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NewV = Builder.CreateSub(Val,
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ConstantInt::get(I.getType(), ~(*Int) + 1));
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} else if (match(&I, m_Sub(m_Value(Val), m_APInt(Int)))
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&& Int->isNegative()) {
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and Int->isNegative()) {
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Builder.SetInsertPoint(&I);
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NewV = Builder.CreateAdd(Val,
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ConstantInt::get(I.getType(), ~(*Int) + 1));
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} else if ((match(&I, m_Mul(m_Value(Val), m_APInt(Int)))
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|| match(&I, m_Mul(m_APInt(Int), m_Value(Val))))
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&& Int->isNegative()) {
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or match(&I, m_Mul(m_APInt(Int), m_Value(Val))))
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and Int->isNegative()) {
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const auto IntType = Val->getType();
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if (Int->isSignBitSet()
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&& Int->isSignedIntN(IntType->getIntegerBitWidth())) {
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auto Call = BuildUnaryMinus(Val, Int);
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NewV = Builder.CreateMul(Val, Call);
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and Int->isSignedIntN(IntType->getIntegerBitWidth())) {
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BuildUnaryMinus.SetInsertPoint(&I);
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auto UnaryMinus = BuildUnaryMinus(Val->getType(), *Int);
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Builder.SetInsertPoint(UnaryMinus->getNextNonDebugInstruction());
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NewV = Builder.CreateMul(Val, UnaryMinus);
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}
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} else if (match(&I, m_SDiv(m_Value(Val), m_APInt(Int)))
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&& Int->isNegative()) {
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and Int->isNegative()) {
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const auto IntType = Val->getType();
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if (Int->isSignBitSet()
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&& Int->isSignedIntN(IntType->getIntegerBitWidth())) {
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auto Call = BuildUnaryMinus(Val, Int);
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NewV = Builder.CreateSDiv(Val, Call);
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and Int->isSignedIntN(IntType->getIntegerBitWidth())) {
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BuildUnaryMinus.SetInsertPoint(&I);
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auto UnaryMinus = BuildUnaryMinus(Val->getType(), *Int);
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Builder.SetInsertPoint(UnaryMinus->getNextNonDebugInstruction());
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NewV = Builder.CreateSDiv(Val, UnaryMinus);
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}
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} else if (match(&I, m_SDiv(m_APInt(Int), m_Value(Val)))
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&& Int->isNegative()) {
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and Int->isNegative()) {
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const auto IntType = Val->getType();
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if (Int->isSignBitSet()
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&& Int->isSignedIntN(IntType->getIntegerBitWidth())) {
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auto Call = BuildUnaryMinus(Val, Int);
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NewV = Builder.CreateSDiv(Call, Val);
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and Int->isSignedIntN(IntType->getIntegerBitWidth())) {
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BuildUnaryMinus.SetInsertPoint(&I);
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auto UnaryMinus = BuildUnaryMinus(Val->getType(), *Int);
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Builder.SetInsertPoint(UnaryMinus->getNextNonDebugInstruction());
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NewV = Builder.CreateSDiv(UnaryMinus, Val);
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}
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} else if (match(&I, m_SRem(m_Value(Val), m_APInt(Int)))
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&& Int->isNegative()) {
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and Int->isNegative()) {
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const auto IntType = Val->getType();
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if (Int->isSignBitSet()
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&& Int->isSignedIntN(IntType->getIntegerBitWidth())) {
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auto Call = BuildUnaryMinus(Val, Int);
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NewV = Builder.CreateSRem(Val, Call);
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and Int->isSignedIntN(IntType->getIntegerBitWidth())) {
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BuildUnaryMinus.SetInsertPoint(&I);
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auto UnaryMinus = BuildUnaryMinus(Val->getType(), *Int);
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Builder.SetInsertPoint(UnaryMinus->getNextNonDebugInstruction());
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NewV = Builder.CreateSRem(Val, UnaryMinus);
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}
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} else if (match(&I, m_SRem(m_APInt(Int), m_Value(Val)))
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&& Int->isNegative()) {
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and Int->isNegative()) {
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const auto IntType = Val->getType();
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if (Int->isSignBitSet()
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&& Int->isSignedIntN(IntType->getIntegerBitWidth())) {
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auto Call = BuildUnaryMinus(Val, Int);
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NewV = Builder.CreateSRem(Call, Val);
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and Int->isSignedIntN(IntType->getIntegerBitWidth())) {
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BuildUnaryMinus.SetInsertPoint(&I);
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auto UnaryMinus = BuildUnaryMinus(Val->getType(), *Int);
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Builder.SetInsertPoint(UnaryMinus->getNextNonDebugInstruction());
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NewV = Builder.CreateSRem(UnaryMinus, Val);
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}
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} else if ((match(&I, m_Xor(m_Value(Val), m_APInt(Int)))
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|| match(&I, m_Xor(m_APInt(Int), m_Value(Val))))
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&& Int->isAllOnesValue()) {
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const auto IntType = I.getType();
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auto Func = BinaryNotPool.get(IntType, IntType, IntType, "binary_not");
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NewV = Builder.CreateCall(Func, { Val });
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} else if (match(&I, m_ICmp(Pred, m_Value(Val), m_APInt(Int)))
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&& Pred == ICmpInst::Predicate::ICMP_EQ) {
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} else if (ICmpInst::Predicate Pred;
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match(&I, m_ICmp(Pred, m_Value(Val), m_APInt(Int)))) {
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const auto IntType = Val->getType();
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if (Int->isSignBitSet()
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&& Int->isSignedIntN(IntType->getIntegerBitWidth())) {
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auto Call = BuildUnaryMinus(Val, Int);
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NewV = Builder.CreateICmp(Pred, Val, Call);
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llvm::Value *LHS = nullptr;
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const APInt *RHS = nullptr;
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if (match(Val, m_Add(m_Value(LHS), m_APInt(RHS)))) {
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bool Overflow = false;
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APInt NewInt = isSignedComparison(Pred) ?
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Int->ssub_ov(*RHS, Overflow) :
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Int->usub_ov(*RHS, Overflow);
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Builder.SetInsertPoint(I.getNextNonDebugInstruction());
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NewV = Builder.CreateICmp(Pred,
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LHS,
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ConstantInt::get(IntType, NewInt));
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if (not isEqualityComparison(Pred) and Overflow) {
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// Here we don't have overflow, and it's not an equality comparison,
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// so we have to handle wraparound
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llvm::ICmpInst::Predicate P;
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switch (Pred) {
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case llvm::ICmpInst::Predicate::ICMP_SGE:
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case llvm::ICmpInst::Predicate::ICMP_SGT: {
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P = llvm::ICmpInst::Predicate::ICMP_SLT;
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} break;
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case llvm::ICmpInst::Predicate::ICMP_UGE:
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case llvm::ICmpInst::Predicate::ICMP_UGT: {
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P = llvm::ICmpInst::Predicate::ICMP_ULT;
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} break;
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case llvm::ICmpInst::Predicate::ICMP_SLE:
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case llvm::ICmpInst::Predicate::ICMP_SLT: {
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P = llvm::ICmpInst::Predicate::ICMP_SGT;
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} break;
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case llvm::ICmpInst::Predicate::ICMP_ULE:
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case llvm::ICmpInst::Predicate::ICMP_ULT: {
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P = llvm::ICmpInst::Predicate::ICMP_UGT;
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} break;
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default:
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revng_abort();
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}
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auto *NotRHS = ConstantInt::get(IntType, ~*RHS);
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NewV = Builder.CreateAnd(NewV, Builder.CreateICmp(P, LHS, NotRHS));
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}
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} else if (match(Val, m_Sub(m_Value(LHS), m_APInt(RHS)))) {
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bool Overflow = false;
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APInt NewInt = isSignedComparison(Pred) ?
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Int->ssub_ov(-*RHS, Overflow) :
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Int->usub_ov(-*RHS, Overflow);
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Builder.SetInsertPoint(I.getNextNonDebugInstruction());
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NewV = Builder.CreateICmp(Pred,
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LHS,
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ConstantInt::get(IntType, NewInt));
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if (not isEqualityComparison(Pred) and Overflow) {
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// Here we don't have overflow, and it's not an equality comparison,
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// so we have to handle wraparound
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llvm::ICmpInst::Predicate P;
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switch (Pred) {
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case llvm::ICmpInst::Predicate::ICMP_SGE:
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case llvm::ICmpInst::Predicate::ICMP_SGT: {
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P = llvm::ICmpInst::Predicate::ICMP_SLT;
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} break;
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case llvm::ICmpInst::Predicate::ICMP_UGE:
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case llvm::ICmpInst::Predicate::ICMP_UGT: {
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P = llvm::ICmpInst::Predicate::ICMP_ULT;
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} break;
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case llvm::ICmpInst::Predicate::ICMP_SLE:
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case llvm::ICmpInst::Predicate::ICMP_SLT: {
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P = llvm::ICmpInst::Predicate::ICMP_SGT;
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} break;
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case llvm::ICmpInst::Predicate::ICMP_ULE:
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case llvm::ICmpInst::Predicate::ICMP_ULT: {
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P = llvm::ICmpInst::Predicate::ICMP_UGT;
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} break;
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default:
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revng_abort();
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}
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auto *NotMinusRHS = ConstantInt::get(IntType, ~-*RHS);
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NewV = Builder.CreateAnd(NewV,
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Builder.CreateICmp(P, LHS, NotMinusRHS));
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}
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} else if (Int->isSignBitSet()
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and Int->isSignedIntN(IntType->getIntegerBitWidth())) {
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BuildUnaryMinus.SetInsertPoint(&I);
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auto UnaryMinus = BuildUnaryMinus(IntType, *Int);
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Builder.SetInsertPoint(UnaryMinus->getNextNonDebugInstruction());
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NewV = Builder.CreateICmp(Pred, Val, UnaryMinus);
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}
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}
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if (NewV) {
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Changed = true;
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I.replaceAllUsesWith(NewV);
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DeadInsts.emplace_back(&I);
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}
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@@ -144,9 +289,9 @@ bool TANP::runOnFunction(llvm::Function &F) {
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}
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for (auto *I : DeadInsts)
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I->eraseFromParent();
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llvm::RecursivelyDeleteTriviallyDeadInstructions(I);
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return not DeadInsts.empty();
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return Changed;
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}
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char TANP::ID = 0;
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