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Implement Transforms/InstCombine/and.ll:test18, a case that occurs 20 times
in perlbmk git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16504 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -897,6 +897,32 @@ static bool isOneBitSet(const ConstantInt *CI) {
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return V && (V & (V-1)) == 0;
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}
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#if 0 // Currently unused
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// isLowOnes - Return true if the constant is of the form 0+1+.
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static bool isLowOnes(const ConstantInt *CI) {
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uint64_t V = CI->getRawValue();
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// There won't be bits set in parts that the type doesn't contain.
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V &= ConstantInt::getAllOnesValue(CI->getType())->getRawValue();
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uint64_t U = V+1; // If it is low ones, this should be a power of two.
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return U && V && (U & V) == 0;
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}
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#endif
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// isHighOnes - Return true if the constant is of the form 1+0+.
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// This is the same as lowones(~X).
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static bool isHighOnes(const ConstantInt *CI) {
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uint64_t V = ~CI->getRawValue();
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// There won't be bits set in parts that the type doesn't contain.
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V &= ConstantInt::getAllOnesValue(CI->getType())->getRawValue();
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uint64_t U = V+1; // If it is low ones, this should be a power of two.
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return U && V && (U & V) == 0;
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}
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/// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
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/// are carefully arranged to allow folding of expressions such as:
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///
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@ -1620,6 +1646,25 @@ Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
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Instruction::SetGE, X,
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Constant::getNullValue(X->getType()));
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}
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// ((X & ~7) == 0) --> X < 7
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if (CI->isNullValue() && isHighOnes(BOC)) {
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Value *X = BO->getOperand(0);
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Constant *NotX = ConstantExpr::getNot(BOC);
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// If 'X' is signed, insert a cast now.
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if (!NotX->getType()->isSigned()) {
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const Type *DestTy = NotX->getType()->getUnsignedVersion();
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CastInst *NewCI = new CastInst(X, DestTy, X->getName()+".uns");
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InsertNewInstBefore(NewCI, I);
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X = NewCI;
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NotX = ConstantExpr::getCast(NotX, DestTy);
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}
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return new SetCondInst(isSetNE ? Instruction::SetGE :
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Instruction::SetLT, X, NotX);
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}
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}
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default: break;
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}
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