From dae90c6afb5f625244c5bb3962669bd1f8a3d5be Mon Sep 17 00:00:00 2001 From: Owen Anderson Date: Tue, 24 Aug 2010 21:59:42 +0000 Subject: Add support for inferring values for the default cases of switches. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111971 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/LazyValueInfo.cpp | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) (limited to 'lib') diff --git a/lib/Analysis/LazyValueInfo.cpp b/lib/Analysis/LazyValueInfo.cpp index 3ecaeed..88fa15a 100644 --- a/lib/Analysis/LazyValueInfo.cpp +++ b/lib/Analysis/LazyValueInfo.cpp @@ -671,9 +671,28 @@ LVILatticeVal LVIQuery::getEdgeValue(BasicBlock *BBFrom, BasicBlock *BBTo) { // If the edge was formed by a switch on the value, then we may know exactly // what it is. if (SwitchInst *SI = dyn_cast(BBFrom->getTerminator())) { - // If BBTo is the default destination of the switch, we don't know anything. - // Given a more powerful range analysis we could know stuff. - if (SI->getCondition() == Val && SI->getDefaultDest() != BBTo) { + // If BBTo is the default destination of the switch, we know that it + // doesn't have the same value as any of the cases. + if (SI->getCondition() == Val) { + if (SI->getDefaultDest() == BBTo) { + const IntegerType *IT = cast(Val->getType()); + ConstantRange CR(IT->getBitWidth()); + + for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) { + const APInt CaseVal = SI->getCaseValue(i)->getValue(); + ConstantRange CaseRange(CaseVal, CaseVal+1); + CaseRange = CaseRange.inverse(); + CR = CR.intersectWith(CaseRange); + } + + LVILatticeVal Result; + if (CR.isFullSet() || CR.isEmptySet()) + Result.markOverdefined(); + else + Result.markConstantRange(CR); + return Result; + } + // We only know something if there is exactly one value that goes from // BBFrom to BBTo. unsigned NumEdges = 0; -- cgit v1.1