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rearrange some code, simplify handling of shifts.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49995 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -599,44 +599,12 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
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}
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}
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if (isa<ConstantExpr>(C1)) {
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// There are many possible foldings we could do here. We should probably
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// at least fold add of a pointer with an integer into the appropriate
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// getelementptr. This will improve alias analysis a bit.
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} else if (isa<ConstantExpr>(C2)) {
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// If C2 is a constant expr and C1 isn't, flop them around and fold the
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// other way if possible.
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switch (Opcode) {
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case Instruction::Add:
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case Instruction::Mul:
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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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// No change of opcode required.
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return ConstantFoldBinaryInstruction(Opcode, C2, C1);
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case Instruction::Shl:
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case Instruction::LShr:
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case Instruction::AShr:
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case Instruction::Sub:
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case Instruction::SDiv:
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case Instruction::UDiv:
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case Instruction::FDiv:
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case Instruction::URem:
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case Instruction::SRem:
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case Instruction::FRem:
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default: // These instructions cannot be flopped around.
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return 0;
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}
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}
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// At this point we know neither constant is an UndefValue nor a ConstantExpr
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// so look at directly computing the value.
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// At this point we know neither constant is an UndefValue.
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if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
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if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
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using namespace APIntOps;
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APInt C1V = CI1->getValue();
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APInt C2V = CI2->getValue();
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const APInt &C1V = CI1->getValue();
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const APInt &C2V = CI2->getValue();
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switch (Opcode) {
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default:
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break;
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@ -672,30 +640,27 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
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return ConstantInt::get(C1V | C2V);
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case Instruction::Xor:
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return ConstantInt::get(C1V ^ C2V);
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case Instruction::Shl:
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if (uint32_t shiftAmt = C2V.getZExtValue()) {
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if (shiftAmt < C1V.getBitWidth())
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return ConstantInt::get(C1V.shl(shiftAmt));
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else
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return UndefValue::get(C1->getType()); // too big shift is undef
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}
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return const_cast<ConstantInt*>(CI1); // Zero shift is identity
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case Instruction::LShr:
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if (uint32_t shiftAmt = C2V.getZExtValue()) {
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if (shiftAmt < C1V.getBitWidth())
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return ConstantInt::get(C1V.lshr(shiftAmt));
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else
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return UndefValue::get(C1->getType()); // too big shift is undef
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}
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return const_cast<ConstantInt*>(CI1); // Zero shift is identity
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case Instruction::AShr:
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if (uint32_t shiftAmt = C2V.getZExtValue()) {
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if (shiftAmt < C1V.getBitWidth())
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return ConstantInt::get(C1V.ashr(shiftAmt));
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else
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return UndefValue::get(C1->getType()); // too big shift is undef
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}
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return const_cast<ConstantInt*>(CI1); // Zero shift is identity
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case Instruction::Shl: {
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uint32_t shiftAmt = C2V.getZExtValue();
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if (shiftAmt < C1V.getBitWidth())
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return ConstantInt::get(C1V.shl(shiftAmt));
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else
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return UndefValue::get(C1->getType()); // too big shift is undef
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}
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case Instruction::LShr: {
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uint32_t shiftAmt = C2V.getZExtValue();
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if (shiftAmt < C1V.getBitWidth())
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return ConstantInt::get(C1V.lshr(shiftAmt));
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else
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return UndefValue::get(C1->getType()); // too big shift is undef
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}
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case Instruction::AShr: {
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uint32_t shiftAmt = C2V.getZExtValue();
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if (shiftAmt < C1V.getBitWidth())
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return ConstantInt::get(C1V.ashr(shiftAmt));
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else
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return UndefValue::get(C1->getType()); // too big shift is undef
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}
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}
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}
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} else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
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@ -769,7 +734,38 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
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}
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}
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// We don't know how to fold this
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if (isa<ConstantExpr>(C1)) {
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// There are many possible foldings we could do here. We should probably
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// at least fold add of a pointer with an integer into the appropriate
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// getelementptr. This will improve alias analysis a bit.
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} else if (isa<ConstantExpr>(C2)) {
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// If C2 is a constant expr and C1 isn't, flop them around and fold the
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// other way if possible.
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switch (Opcode) {
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case Instruction::Add:
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case Instruction::Mul:
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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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// No change of opcode required.
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return ConstantFoldBinaryInstruction(Opcode, C2, C1);
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case Instruction::Shl:
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case Instruction::LShr:
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case Instruction::AShr:
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case Instruction::Sub:
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case Instruction::SDiv:
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case Instruction::UDiv:
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case Instruction::FDiv:
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case Instruction::URem:
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case Instruction::SRem:
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case Instruction::FRem:
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default: // These instructions cannot be flopped around.
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break;
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}
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}
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// We don't know how to fold this.
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return 0;
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}
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