Fix for pr24866

[oota-llvm.git] / lib / Analysis / ValueTracking.cpp

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 7000210e1faad76c8276c643217256e63673e82d..10776a03cae36ff09fff3994ea75551d5b7a6da1 100644 (file)
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -328,7 +328,7 @@ static void computeKnownBitsMul(Value *Op0, Value *Op1, bool NSW,
   }
 
   // If low bits are zero in either operand, output low known-0 bits.
-  // Also compute a conserative estimate for high known-0 bits.
+  // Also compute a conservative estimate for high known-0 bits.
   // More trickiness is possible, but this is sufficient for the
   // interesting case of alignment computation.
   KnownOne.clearAllBits();
@@ -609,6 +609,11 @@ static void computeKnownBitsFromDominatingCondition(Value *V, APInt &KnownZero,
   if (!Q.DT || !Q.CxtI)
     return;
   Instruction *Cxt = const_cast<Instruction *>(Q.CxtI);
+  // The context instruction might be in a statically unreachable block.  If
+  // so, asking dominator queries may yield suprising results.  (e.g. the block
+  // may not have a dom tree node)
+  if (!Q.DT->isReachableFromEntry(Cxt->getParent()))
+    return;
 
   // Avoid useless work
   if (auto VI = dyn_cast<Instruction>(V))
@@ -655,7 +660,9 @@ static void computeKnownBitsFromDominatingCondition(Value *V, APInt &KnownZero,
     // instruction.  Finding a condition where one path dominates the context
     // isn't enough because both the true and false cases could merge before
     // the context instruction we're actually interested in.  Instead, we need
-    // to ensure that the taken *edge* dominates the context instruction.
+    // to ensure that the taken *edge* dominates the context instruction.  We
+    // know that the edge must be reachable since we started from a reachable
+    // block.
     BasicBlock *BB0 = BI->getSuccessor(0);
     BasicBlockEdge Edge(BI->getParent(), BB0);
     if (!Edge.isSingleEdge() || !Q.DT->dominates(Edge, Q.CxtI->getParent()))
@@ -2952,6 +2959,8 @@ static bool isAligned(const Value *Base, APInt Offset, unsigned Align,
     BaseAlign = GV->getAlignment();
   else if (const Argument *A = dyn_cast<Argument>(Base))
     BaseAlign = A->getParamAlignment();
+  else if (auto CS = ImmutableCallSite(Base))
+    BaseAlign = CS.getAttributes().getParamAlignment(AttributeSet::ReturnIndex);
 
   if (!BaseAlign) {
     Type *Ty = Base->getType()->getPointerElementType();
@@ -3220,6 +3229,8 @@ bool llvm::mayBeMemoryDependent(const Instruction &I) {
 
 /// Return true if we know that the specified value is never null.
 bool llvm::isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI) {
+  assert(V->getType()->isPointerTy() && "V must be pointer type");
+
   // Alloca never returns null, malloc might.
   if (isa<AllocaInst>(V)) return true;
 
@@ -3252,6 +3263,8 @@ bool llvm::isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI) {
 static bool isKnownNonNullFromDominatingCondition(const Value *V,
                                                   const Instruction *CtxI,
                                                   const DominatorTree *DT) {
+  assert(V->getType()->isPointerTy() && "V must be pointer type");
+
   unsigned NumUsesExplored = 0;
   for (auto U : V->users()) {
     // Avoid massive lists