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Fix InstCombine/2004-02-23-ShiftShiftOverflow.ll
Also, turn 'shr int %X, 1234' into 'shr int %X, 31' git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11768 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -1570,9 +1570,14 @@ Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
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// of a signed value.
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//
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unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
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if (CUI->getValue() >= TypeBits &&
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(!Op0->getType()->isSigned() || isLeftShift))
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return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
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if (CUI->getValue() >= TypeBits) {
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if (!Op0->getType()->isSigned() || isLeftShift)
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return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
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else {
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I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
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return &I;
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}
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}
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// ((X*C1) << C2) == (X * (C1 << C2))
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if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
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@ -1636,6 +1641,8 @@ Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
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// Check for (A << c1) << c2 and (A >> c1) >> c2
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if (I.getOpcode() == Op0SI->getOpcode()) {
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unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
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if (Op0->getType()->getPrimitiveSize()*8 < Amt)
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Amt = Op0->getType()->getPrimitiveSize()*8;
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return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
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ConstantUInt::get(Type::UByteTy, Amt));
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}
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