mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2025-02-08 21:32:39 +00:00
Implement XOR reassociation. It is based on following rules:
rule 1: (x | c1) ^ c2 => (x & ~c1) ^ (c1^c2),
only useful when c1=c2
rule 2: (x & c1) ^ (x & c2) = (x & (c1^c2))
rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
rule 4: (x | c1) ^ (x & c2) => (x & c3) ^ c1, where c3 = ~c1 ^ c2
It reduces an application's size (in terms of # of instructions) by 8.9%.
Reviwed by Pete Cooper. Thanks a lot!
rdar://13212115
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178409 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Shuxin Yang
parent
fd2cd0db97
commit
2d10010649
@ -110,6 +110,51 @@ namespace {
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}
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};
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};
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/// Utility class representing a non-constant Xor-operand. We classify
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/// non-constant Xor-Operands into two categories:
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/// C1) The operand is in the form "X & C", where C is a constant and C != ~0
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/// C2)
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/// C2.1) The operand is in the form of "X | C", where C is a non-zero
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/// constant.
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/// C2.2) Any operand E which doesn't fall into C1 and C2.1, we view this
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/// operand as "E | 0"
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class XorOpnd {
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public:
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XorOpnd(Value *V);
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const XorOpnd &operator=(const XorOpnd &That);
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bool isInvalid() const { return SymbolicPart == 0; }
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bool isOrExpr() const { return isOr; }
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Value *getValue() const { return OrigVal; }
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Value *getSymbolicPart() const { return SymbolicPart; }
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unsigned getSymbolicRank() const { return SymbolicRank; }
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const APInt &getConstPart() const { return ConstPart; }
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void Invalidate() { SymbolicPart = OrigVal = 0; }
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void setSymbolicRank(unsigned R) { SymbolicRank = R; }
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// Sort the XorOpnd-Pointer in ascending order of symbolic-value-rank.
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// The purpose is twofold:
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// 1) Cluster together the operands sharing the same symbolic-value.
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// 2) Operand having smaller symbolic-value-rank is permuted earlier, which
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// could potentially shorten crital path, and expose more loop-invariants.
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// Note that values' rank are basically defined in RPO order (FIXME).
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// So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier
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// than Y which is defined earlier than Z. Permute "x | 1", "Y & 2",
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// "z" in the order of X-Y-Z is better than any other orders.
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struct PtrSortFunctor {
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bool operator()(XorOpnd * const &LHS, XorOpnd * const &RHS) {
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return LHS->getSymbolicRank() < RHS->getSymbolicRank();
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}
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};
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private:
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Value *OrigVal;
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Value *SymbolicPart;
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APInt ConstPart;
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unsigned SymbolicRank;
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bool isOr;
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};
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}
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namespace {
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@ -137,6 +182,11 @@ namespace {
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Value *OptimizeExpression(BinaryOperator *I,
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SmallVectorImpl<ValueEntry> &Ops);
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Value *OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
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Value *OptimizeXor(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
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bool CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, APInt &ConstOpnd,
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Value *&Res);
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bool CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
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APInt &ConstOpnd, Value *&Res);
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bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
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SmallVectorImpl<Factor> &Factors);
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Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder,
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@ -148,6 +198,42 @@ namespace {
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};
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}
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XorOpnd::XorOpnd(Value *V) {
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assert(!isa<Constant>(V) && "No constant");
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OrigVal = V;
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Instruction *I = dyn_cast<Instruction>(V);
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SymbolicRank = 0;
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if (I && (I->getOpcode() == Instruction::Or ||
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I->getOpcode() == Instruction::And)) {
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Value *V0 = I->getOperand(0);
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Value *V1 = I->getOperand(1);
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if (isa<ConstantInt>(V0))
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std::swap(V0, V1);
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if (ConstantInt *C = dyn_cast<ConstantInt>(V1)) {
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ConstPart = C->getValue();
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SymbolicPart = V0;
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isOr = (I->getOpcode() == Instruction::Or);
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return;
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}
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}
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// view the operand as "V | 0"
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SymbolicPart = V;
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ConstPart = APInt::getNullValue(V->getType()->getIntegerBitWidth());
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isOr = true;
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}
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const XorOpnd &XorOpnd::operator=(const XorOpnd &That) {
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OrigVal = That.OrigVal;
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SymbolicPart = That.SymbolicPart;
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ConstPart = That.ConstPart;
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SymbolicRank = That.SymbolicRank;
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isOr = That.isOr;
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return *this;
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}
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char Reassociate::ID = 0;
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INITIALIZE_PASS(Reassociate, "reassociate",
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"Reassociate expressions", false, false)
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@ -1040,6 +1126,240 @@ static Value *OptimizeAndOrXor(unsigned Opcode,
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return 0;
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}
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/// Helper funciton of CombineXorOpnd(). It creates a bitwise-and
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/// instruction with the given two operands, and return the resulting
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/// instruction. There are two special cases: 1) if the constant operand is 0,
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/// it will return NULL. 2) if the constant is ~0, the symbolic operand will
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/// be returned.
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static Value *createAndInstr(Instruction *InsertBefore, Value *Opnd,
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const APInt &ConstOpnd) {
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if (ConstOpnd != 0) {
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if (!ConstOpnd.isAllOnesValue()) {
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LLVMContext &Ctx = Opnd->getType()->getContext();
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Instruction *I;
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I = BinaryOperator::CreateAnd(Opnd, ConstantInt::get(Ctx, ConstOpnd),
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"and.ra", InsertBefore);
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I->setDebugLoc(InsertBefore->getDebugLoc());
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return I;
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}
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return Opnd;
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}
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return 0;
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}
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// Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd"
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// into "R ^ C", where C would be 0, and R is a symbolic value.
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//
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// If it was successful, true is returned, and the "R" and "C" is returned
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// via "Res" and "ConstOpnd", respectively; otherwise, false is returned,
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// and both "Res" and "ConstOpnd" remain unchanged.
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//
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bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
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APInt &ConstOpnd, Value *&Res) {
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// Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2
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// = ((x | c1) ^ c1) ^ (c1 ^ c2)
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// = (x & ~c1) ^ (c1 ^ c2)
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// It is useful only when c1 == c2.
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if (Opnd1->isOrExpr() && Opnd1->getConstPart() != 0) {
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if (!Opnd1->getValue()->hasOneUse())
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return false;
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const APInt &C1 = Opnd1->getConstPart();
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if (C1 != ConstOpnd)
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return false;
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Value *X = Opnd1->getSymbolicPart();
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Res = createAndInstr(I, X, ~C1);
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// ConstOpnd was C2, now C1 ^ C2.
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ConstOpnd ^= C1;
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if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
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RedoInsts.insert(T);
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return true;
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}
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return false;
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}
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// Helper function of OptimizeXor(). It tries to simplify
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// "Opnd1 ^ Opnd2 ^ ConstOpnd" into "R ^ C", where C would be 0, and R is a
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// symbolic value.
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//
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// If it was successful, true is returned, and the "R" and "C" is returned
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// via "Res" and "ConstOpnd", respectively (If the entire expression is
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// evaluated to a constant, the Res is set to NULL); otherwise, false is
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// returned, and both "Res" and "ConstOpnd" remain unchanged.
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bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
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APInt &ConstOpnd, Value *&Res) {
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Value *X = Opnd1->getSymbolicPart();
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if (X != Opnd2->getSymbolicPart())
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return false;
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const APInt &C1 = Opnd1->getConstPart();
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const APInt &C2 = Opnd2->getConstPart();
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// This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.)
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int DeadInstNum = 1;
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if (Opnd1->getValue()->hasOneUse())
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DeadInstNum++;
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if (Opnd2->getValue()->hasOneUse())
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DeadInstNum++;
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// Xor-Rule 2:
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// (x | c1) ^ (x & c2)
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// = (x|c1) ^ (x&c2) ^ (c1 ^ c1) = ((x|c1) ^ c1) ^ (x & c2) ^ c1
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// = (x & ~c1) ^ (x & c2) ^ c1 // Xor-Rule 1
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// = (x & c3) ^ c1, where c3 = ~c1 ^ c2 // Xor-rule 3
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//
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if (Opnd1->isOrExpr() != Opnd2->isOrExpr()) {
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if (Opnd2->isOrExpr())
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std::swap(Opnd1, Opnd2);
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APInt C3((~C1) ^ C2);
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// Do not increase code size!
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if (C3 != 0 && !C3.isAllOnesValue()) {
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int NewInstNum = ConstOpnd != 0 ? 1 : 2;
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if (NewInstNum > DeadInstNum)
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return false;
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}
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Res = createAndInstr(I, X, C3);
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ConstOpnd ^= C1;
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} else if (Opnd1->isOrExpr()) {
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// Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
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//
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APInt C3 = C1 ^ C2;
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// Do not increase code size
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if (C3 != 0 && !C3.isAllOnesValue()) {
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int NewInstNum = ConstOpnd != 0 ? 1 : 2;
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if (NewInstNum > DeadInstNum)
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return false;
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}
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Res = createAndInstr(I, X, C3);
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ConstOpnd ^= C3;
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} else {
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// Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
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//
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APInt C3 = C1 ^ C2;
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Res = createAndInstr(I, X, C3);
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}
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// Put the original operands in the Redo list; hope they will be deleted
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// as dead code.
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if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
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RedoInsts.insert(T);
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if (Instruction *T = dyn_cast<Instruction>(Opnd2->getValue()))
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RedoInsts.insert(T);
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return true;
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}
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/// Optimize a series of operands to an 'xor' instruction. If it can be reduced
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/// to a single Value, it is returned, otherwise the Ops list is mutated as
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/// necessary.
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Value *Reassociate::OptimizeXor(Instruction *I,
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SmallVectorImpl<ValueEntry> &Ops) {
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if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops))
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return V;
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if (Ops.size() == 1)
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return 0;
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SmallVector<XorOpnd, 8> Opnds;
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SmallVector<XorOpnd*, 8> OpndPtrs;
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Type *Ty = Ops[0].Op->getType();
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APInt ConstOpnd(Ty->getIntegerBitWidth(), 0);
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// Step 1: Convert ValueEntry to XorOpnd
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for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
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Value *V = Ops[i].Op;
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if (!isa<ConstantInt>(V)) {
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XorOpnd O(V);
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O.setSymbolicRank(getRank(O.getSymbolicPart()));
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Opnds.push_back(O);
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OpndPtrs.push_back(&Opnds.back());
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} else
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ConstOpnd ^= cast<ConstantInt>(V)->getValue();
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}
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// Step 2: Sort the Xor-Operands in a way such that the operands containing
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// the same symbolic value cluster together. For instance, the input operand
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// sequence ("x | 123", "y & 456", "x & 789") will be sorted into:
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// ("x | 123", "x & 789", "y & 456").
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std::sort(OpndPtrs.begin(), OpndPtrs.end(), XorOpnd::PtrSortFunctor());
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// Step 3: Combine adjacent operands
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XorOpnd *PrevOpnd = 0;
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bool Changed = false;
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for (unsigned i = 0, e = Opnds.size(); i < e; i++) {
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XorOpnd *CurrOpnd = OpndPtrs[i];
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// The combined value
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Value *CV;
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// Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd"
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if (ConstOpnd != 0 && CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) {
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Changed = true;
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if (CV)
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*CurrOpnd = XorOpnd(CV);
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else {
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CurrOpnd->Invalidate();
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continue;
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}
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}
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if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) {
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PrevOpnd = CurrOpnd;
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continue;
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}
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// step 3.2: When previous and current operands share the same symbolic
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// value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd"
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//
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if (CombineXorOpnd(I, CurrOpnd, PrevOpnd, ConstOpnd, CV)) {
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// Remove previous operand
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PrevOpnd->Invalidate();
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if (CV) {
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*CurrOpnd = XorOpnd(CV);
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PrevOpnd = CurrOpnd;
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} else {
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CurrOpnd->Invalidate();
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PrevOpnd = 0;
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}
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Changed = true;
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}
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}
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// Step 4: Reassemble the Ops
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if (Changed) {
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Ops.clear();
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for (unsigned int i = 0, e = Opnds.size(); i < e; i++) {
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XorOpnd &O = Opnds[i];
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if (O.isInvalid())
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continue;
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ValueEntry VE(getRank(O.getValue()), O.getValue());
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Ops.push_back(VE);
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}
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if (ConstOpnd != 0) {
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Value *C = ConstantInt::get(Ty->getContext(), ConstOpnd);
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ValueEntry VE(getRank(C), C);
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Ops.push_back(VE);
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}
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int Sz = Ops.size();
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if (Sz == 1)
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return Ops.back().Op;
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else if (Sz == 0) {
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assert(ConstOpnd == 0);
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return ConstantInt::get(Ty->getContext(), ConstOpnd);
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}
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}
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return 0;
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}
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/// OptimizeAdd - Optimize a series of operands to an 'add' instruction. This
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/// optimizes based on identities. If it can be reduced to a single Value, it
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/// is returned, otherwise the Ops list is mutated as necessary.
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@ -1431,11 +1751,15 @@ Value *Reassociate::OptimizeExpression(BinaryOperator *I,
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default: break;
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case Instruction::And:
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case Instruction::Or:
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case Instruction::Xor:
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if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
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return Result;
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break;
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case Instruction::Xor:
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if (Value *Result = OptimizeXor(I, Ops))
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return Result;
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break;
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case Instruction::Add:
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if (Value *Result = OptimizeAdd(I, Ops))
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return Result;
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151
test/Transforms/Reassociate/xor_reassoc.ll
Normal file
151
test/Transforms/Reassociate/xor_reassoc.ll
Normal file
@ -0,0 +1,151 @@
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;RUN: opt -S -reassociate < %s | FileCheck %s
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; ==========================================================================
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;
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; Xor reassociation general cases
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;
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; ==========================================================================
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; (x | c1) ^ (x | c2) => (x & c3) ^ c3, where c3 = c1^c2
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;
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define i32 @xor1(i32 %x) {
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%or = or i32 %x, 123
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%or1 = or i32 %x, 456
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%xor = xor i32 %or, %or1
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ret i32 %xor
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;CHECK: @xor1
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;CHECK: %and.ra = and i32 %x, 435
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;CHECK: %xor = xor i32 %and.ra, 435
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}
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; Test rule : (x & c1) ^ (x & c2) = (x & (c1^c2))
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; Real testing case : (x & 123) ^ y ^ (x & 345) => (x & 435) ^ y
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define i32 @xor2(i32 %x, i32 %y) {
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%and = and i32 %x, 123
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%xor = xor i32 %and, %y
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%and1 = and i32 %x, 456
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%xor2 = xor i32 %xor, %and1
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ret i32 %xor2
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;CHECK: @xor2
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;CHECK: %and.ra = and i32 %x, 435
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;CHECK: %xor2 = xor i32 %and.ra, %y
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}
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; Test rule: (x | c1) ^ (x & c2) = (x & c3) ^ c1, where c3 = ~c1 ^ c2
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; c3 = ~c1 ^ c2
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define i32 @xor3(i32 %x, i32 %y) {
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%or = or i32 %x, 123
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%xor = xor i32 %or, %y
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%and = and i32 %x, 456
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%xor1 = xor i32 %xor, %and
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ret i32 %xor1
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;CHECK: @xor3
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;CHECK: %and.ra = and i32 %x, -436
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;CHECK: %xor = xor i32 %y, 123
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;CHECK: %xor1 = xor i32 %xor, %and.ra
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}
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; Test rule: (x | c1) ^ c2 = (x & ~c1) ^ (c1 ^ c2)
|
||||
define i32 @xor4(i32 %x, i32 %y) {
|
||||
%and = and i32 %x, -124
|
||||
%xor = xor i32 %y, 435
|
||||
%xor1 = xor i32 %xor, %and
|
||||
ret i32 %xor1
|
||||
; CHECK: @xor4
|
||||
; CHECK: %and = and i32 %x, -124
|
||||
; CHECK: %xor = xor i32 %y, 435
|
||||
; CHECK: %xor1 = xor i32 %xor, %and
|
||||
}
|
||||
|
||||
; ==========================================================================
|
||||
;
|
||||
; Xor reassociation special cases
|
||||
;
|
||||
; ==========================================================================
|
||||
|
||||
; Special case1:
|
||||
; (x | c1) ^ (x & ~c1) = c1
|
||||
define i32 @xor_special1(i32 %x, i32 %y) {
|
||||
%or = or i32 %x, 123
|
||||
%xor = xor i32 %or, %y
|
||||
%and = and i32 %x, -124
|
||||
%xor1 = xor i32 %xor, %and
|
||||
ret i32 %xor1
|
||||
; CHECK: @xor_special1
|
||||
; CHECK: %xor1 = xor i32 %y, 123
|
||||
; CHECK: ret i32 %xor1
|
||||
}
|
||||
|
||||
; Special case1:
|
||||
; (x | c1) ^ (x & c1) = x ^ c1
|
||||
define i32 @xor_special2(i32 %x, i32 %y) {
|
||||
%or = or i32 %x, 123
|
||||
%xor = xor i32 %or, %y
|
||||
%and = and i32 %x, 123
|
||||
%xor1 = xor i32 %xor, %and
|
||||
ret i32 %xor1
|
||||
; CHECK: @xor_special2
|
||||
; CHECK: %xor = xor i32 %y, 123
|
||||
; CHECK: %xor1 = xor i32 %xor, %x
|
||||
; CHECK: ret i32 %xor1
|
||||
}
|
||||
|
||||
; (x | c1) ^ (x | c1) => 0
|
||||
define i32 @xor_special3(i32 %x) {
|
||||
%or = or i32 %x, 123
|
||||
%or1 = or i32 %x, 123
|
||||
%xor = xor i32 %or, %or1
|
||||
ret i32 %xor
|
||||
;CHECK: @xor_special3
|
||||
;CHECK: ret i32 0
|
||||
}
|
||||
|
||||
; (x & c1) ^ (x & c1) => 0
|
||||
define i32 @xor_special4(i32 %x) {
|
||||
%or = and i32 %x, 123
|
||||
%or1 = and i32 123, %x
|
||||
%xor = xor i32 %or, %or1
|
||||
ret i32 %xor
|
||||
;CHECK: @xor_special4
|
||||
;CHECK: ret i32 0
|
||||
}
|
||||
|
||||
; ==========================================================================
|
||||
;
|
||||
; Xor reassociation curtail code size
|
||||
;
|
||||
; ==========================================================================
|
||||
|
||||
; (x | c1) ^ (x | c2) => (x & c3) ^ c3
|
||||
; is enabled if one of operands has multiple uses
|
||||
;
|
||||
define i32 @xor_ra_size1(i32 %x) {
|
||||
%or = or i32 %x, 123
|
||||
%or1 = or i32 %x, 456
|
||||
%xor = xor i32 %or, %or1
|
||||
|
||||
%add = add i32 %xor, %or
|
||||
ret i32 %add
|
||||
;CHECK: @xor_ra_size1
|
||||
;CHECK: %xor = xor i32 %and.ra, 435
|
||||
}
|
||||
|
||||
; (x | c1) ^ (x | c2) => (x & c3) ^ c3
|
||||
; is disenabled if bothf operands has multiple uses.
|
||||
;
|
||||
define i32 @xor_ra_size2(i32 %x) {
|
||||
%or = or i32 %x, 123
|
||||
%or1 = or i32 %x, 456
|
||||
%xor = xor i32 %or, %or1
|
||||
|
||||
%add = add i32 %xor, %or
|
||||
%add2 = add i32 %add, %or1
|
||||
ret i32 %add2
|
||||
|
||||
;CHECK: @xor_ra_size2
|
||||
;CHECK: %or1 = or i32 %x, 456
|
||||
;CHECK: %xor = xor i32 %or, %or1
|
||||
}
|
||||
Loading…
x
Reference in New Issue
Block a user