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https://github.com/c64scene-ar/llvm-6502.git
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Compile
struct S { unsigned int i : 6, j : 11, k : 15; } b; void plus2 (unsigned int x) { b.j += x; } to: plus2: mov %EAX, DWORD PTR [b] mov %ECX, %EAX and %ECX, 131008 mov %EDX, DWORD PTR [%ESP + 4] shl %EDX, 6 add %EDX, %ECX and %EDX, 131008 and %EAX, -131009 or %EDX, %EAX mov DWORD PTR [b], %EDX ret instead of: plus2: mov %EAX, DWORD PTR [b] mov %ECX, %EAX shr %ECX, 6 and %ECX, 2047 add %ECX, DWORD PTR [%ESP + 4] shl %ECX, 6 and %ECX, 131008 and %EAX, -131009 or %ECX, %EAX mov DWORD PTR [b], %ECX ret git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23385 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -3364,6 +3364,8 @@ Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
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if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0)) {
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// Turn ((X >> C) + Y) << C -> (X + (Y << C)) & (~0 << C)
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Value *V1, *V2, *V3;
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ConstantInt *CC;
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switch (Op0BO->getOpcode()) {
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default: break;
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case Instruction::Add:
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@ -3372,39 +3374,76 @@ Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
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case Instruction::Xor:
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// These operators commute.
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// Turn (Y + (X >> C)) << C -> (X + (Y << C)) & (~0 << C)
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if (ShiftInst *XS = dyn_cast<ShiftInst>(Op0BO->getOperand(1)))
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if (isLeftShift && XS->hasOneUse() && XS->getOperand(1) == CUI &&
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XS->getOpcode() == Instruction::Shr) {
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Instruction *YS = new ShiftInst(Instruction::Shl,
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Op0BO->getOperand(0), CUI,
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Op0BO->getName());
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InsertNewInstBefore(YS, I); // (Y << C)
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Instruction *X = BinaryOperator::create(Op0BO->getOpcode(), YS,
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XS->getOperand(0),
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XS->getName());
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InsertNewInstBefore(X, I); // (X + (Y << C))
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Constant *C2 = ConstantInt::getAllOnesValue(X->getType());
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C2 = ConstantExpr::getShl(C2, CUI);
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return BinaryOperator::createAnd(X, C2);
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}
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// Fall through.
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if (isLeftShift && Op0BO->getOperand(1)->hasOneUse() &&
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match(Op0BO->getOperand(1),
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m_Shr(m_Value(V1), m_ConstantInt(CC))) && CC == CUI) {
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Instruction *YS = new ShiftInst(Instruction::Shl,
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Op0BO->getOperand(0), CUI,
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Op0BO->getName());
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InsertNewInstBefore(YS, I); // (Y << C)
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Instruction *X = BinaryOperator::create(Op0BO->getOpcode(), YS,
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V1,
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Op0BO->getOperand(1)->getName());
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InsertNewInstBefore(X, I); // (X + (Y << C))
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Constant *C2 = ConstantInt::getAllOnesValue(X->getType());
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C2 = ConstantExpr::getShl(C2, CUI);
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return BinaryOperator::createAnd(X, C2);
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}
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// Turn (Y + ((X >> C) & CC)) << C -> ((X & (CC << C)) + (Y << C))
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if (isLeftShift && Op0BO->getOperand(1)->hasOneUse() &&
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match(Op0BO->getOperand(1),
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m_And(m_Shr(m_Value(V1), m_Value(V2)),
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m_ConstantInt(CC))) && V2 == CUI &&
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cast<BinaryOperator>(Op0BO->getOperand(1))->getOperand(0)->hasOneUse()) {
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Instruction *YS = new ShiftInst(Instruction::Shl,
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Op0BO->getOperand(0), CUI,
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Op0BO->getName());
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InsertNewInstBefore(YS, I); // (Y << C)
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Instruction *XM =
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BinaryOperator::createAnd(V1, ConstantExpr::getShl(CC, CUI),
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V1->getName()+".mask");
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InsertNewInstBefore(XM, I); // X & (CC << C)
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return BinaryOperator::create(Op0BO->getOpcode(), YS, XM);
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}
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// FALL THROUGH.
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case Instruction::Sub:
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// Turn ((X >> C) + Y) << C -> (X + (Y << C)) & (~0 << C)
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if (ShiftInst *XS = dyn_cast<ShiftInst>(Op0BO->getOperand(0)))
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if (isLeftShift && XS->hasOneUse() && XS->getOperand(1) == CUI &&
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XS->getOpcode() == Instruction::Shr) {
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Instruction *YS = new ShiftInst(Instruction::Shl,
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Op0BO->getOperand(1), CUI,
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Op0BO->getName());
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InsertNewInstBefore(YS, I); // (Y << C)
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Instruction *X = BinaryOperator::create(Op0BO->getOpcode(), YS,
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XS->getOperand(0),
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XS->getName());
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InsertNewInstBefore(X, I); // (X + (Y << C))
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Constant *C2 = ConstantInt::getAllOnesValue(X->getType());
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C2 = ConstantExpr::getShl(C2, CUI);
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return BinaryOperator::createAnd(X, C2);
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}
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if (isLeftShift && Op0BO->getOperand(0)->hasOneUse() &&
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match(Op0BO->getOperand(0),
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m_Shr(m_Value(V1), m_ConstantInt(CC))) && CC == CUI) {
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Instruction *YS = new ShiftInst(Instruction::Shl,
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Op0BO->getOperand(1), CUI,
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Op0BO->getName());
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InsertNewInstBefore(YS, I); // (Y << C)
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Instruction *X = BinaryOperator::create(Op0BO->getOpcode(), YS,
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V1,
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Op0BO->getOperand(0)->getName());
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InsertNewInstBefore(X, I); // (X + (Y << C))
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Constant *C2 = ConstantInt::getAllOnesValue(X->getType());
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C2 = ConstantExpr::getShl(C2, CUI);
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return BinaryOperator::createAnd(X, C2);
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}
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if (isLeftShift && Op0BO->getOperand(0)->hasOneUse() &&
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match(Op0BO->getOperand(0),
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m_And(m_Shr(m_Value(V1), m_Value(V2)),
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m_ConstantInt(CC))) && V2 == CUI &&
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cast<BinaryOperator>(Op0BO->getOperand(0))->getOperand(0)->hasOneUse()) {
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Instruction *YS = new ShiftInst(Instruction::Shl,
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Op0BO->getOperand(1), CUI,
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Op0BO->getName());
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InsertNewInstBefore(YS, I); // (Y << C)
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Instruction *XM =
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BinaryOperator::createAnd(V1, ConstantExpr::getShl(CC, CUI),
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V1->getName()+".mask");
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InsertNewInstBefore(XM, I); // X & (CC << C)
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return BinaryOperator::create(Op0BO->getOpcode(), YS, XM);
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}
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break;
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}
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