move decomposeBitTestICmp() to Transforms/Utils; NFC
As noted in https://reviews.llvm.org/D22537 , we can use this functionality in
visitSelectInstWithICmp() and InstSimplify, but currently we have duplicated
code.
llvm-svn: 276140
diff --git a/llvm/lib/Transforms/Utils/CmpInstAnalysis.cpp b/llvm/lib/Transforms/Utils/CmpInstAnalysis.cpp
index 0b13005..60ae374 100644
--- a/llvm/lib/Transforms/Utils/CmpInstAnalysis.cpp
+++ b/llvm/lib/Transforms/Utils/CmpInstAnalysis.cpp
@@ -62,3 +62,47 @@
(CmpInst::isSigned(p1) && ICmpInst::isEquality(p2)) ||
(CmpInst::isSigned(p2) && ICmpInst::isEquality(p1));
}
+
+bool llvm::decomposeBitTestICmp(const ICmpInst *I, CmpInst::Predicate &Pred,
+ Value *&X, Value *&Y, Value *&Z) {
+ ConstantInt *C = dyn_cast<ConstantInt>(I->getOperand(1));
+ if (!C)
+ return false;
+
+ switch (I->getPredicate()) {
+ default:
+ return false;
+ case ICmpInst::ICMP_SLT:
+ // X < 0 is equivalent to (X & SignBit) != 0.
+ if (!C->isZero())
+ return false;
+ Y = ConstantInt::get(I->getContext(), APInt::getSignBit(C->getBitWidth()));
+ Pred = ICmpInst::ICMP_NE;
+ break;
+ case ICmpInst::ICMP_SGT:
+ // X > -1 is equivalent to (X & SignBit) == 0.
+ if (!C->isAllOnesValue())
+ return false;
+ Y = ConstantInt::get(I->getContext(), APInt::getSignBit(C->getBitWidth()));
+ Pred = ICmpInst::ICMP_EQ;
+ break;
+ case ICmpInst::ICMP_ULT:
+ // X <u 2^n is equivalent to (X & ~(2^n-1)) == 0.
+ if (!C->getValue().isPowerOf2())
+ return false;
+ Y = ConstantInt::get(I->getContext(), -C->getValue());
+ Pred = ICmpInst::ICMP_EQ;
+ break;
+ case ICmpInst::ICMP_UGT:
+ // X >u 2^n-1 is equivalent to (X & ~(2^n-1)) != 0.
+ if (!(C->getValue() + 1).isPowerOf2())
+ return false;
+ Y = ConstantInt::get(I->getContext(), ~C->getValue());
+ Pred = ICmpInst::ICMP_NE;
+ break;
+ }
+
+ X = I->getOperand(0);
+ Z = ConstantInt::getNullValue(C->getType());
+ return true;
+}