[LVI] Add an API to LazyValueInfo so that it can export ConstantRanges

that it computes. Currently this is used for testing and precision
tuning, but it might be used by optimizations later.

Differential Revision: http://reviews.llvm.org/D19179

llvm-svn: 268291

include/llvm/Analysis/LazyValueInfo.h

@@ -20,6 +20,7 @@
 namespace llvm {
   class AssumptionCache;
   class Constant;
+  class ConstantRange;
   class DataLayout;
   class DominatorTree;
   class Instruction;
@@ -65,6 +66,11 @@ public:
   /// constant at the end of the specified block.  Return null if not.
   Constant *getConstant(Value *V, BasicBlock *BB, Instruction *CxtI = nullptr);
 
+  /// Return the ConstantRange constraint that is known to hold for the
+  /// specified value at the end of the specified block. This may only be called
+  /// on integer-typed Values.
+  ConstantRange getConstantRange(Value *V, BasicBlock *BB, Instruction *CxtI = nullptr);
+
   /// Determine whether the specified value is known to be a
   /// constant on the specified edge.  Return null if not.
   Constant *getConstantOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB,

lib/Analysis/LazyValueInfo.cpp

@@ -1485,6 +1485,22 @@ Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB,
   return nullptr;
 }
 
+ConstantRange LazyValueInfo::getConstantRange(Value *V, BasicBlock *BB,
+					      Instruction *CxtI) {
+  assert(V->getType()->isIntegerTy());
+  unsigned Width = V->getType()->getIntegerBitWidth();
+  const DataLayout &DL = BB->getModule()->getDataLayout();
+  LVILatticeVal Result =
+      getCache(PImpl, AC, &DL, DT).getValueInBlock(V, BB, CxtI);
+  assert(!Result.isConstant());
+  if (Result.isUndefined())
+    return ConstantRange(Width, /*isFullSet=*/false);
+  if (Result.isConstantRange())
+    return Result.getConstantRange();
+  else
+    return ConstantRange(Width, /*isFullSet=*/true);
+}
+
 /// Determine whether the specified value is known to be a
 /// constant on the specified edge. Return null if not.
 Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,