export ConstantRange from LVI

[regehr]

Summary

LVI had no facility to let clients see the ConstantRanges that it compues, this fixes that.

Example client is a pass I'm writing that looks for LVI bugs by asserting that every value for which a nontrivial ConstantRange exists is within the specified bounds.

[reames]

LGTM

I'd really like to see a test case for this. I'm accepting the change without it, but finding a way to test this in tree would be good. Unfortunately, we don't appear to have any of the harness needed for this.

lib/Analysis/LazyValueInfo.cpp

1405

This case should be dead. Assert(!isConstant)

1408

else if

[regehr]

Addresses Philip's comments. Thanks!

[regehr]

I agree that tests would be good, thanks for confirming that I hadn't simply failed to spot the infrastructure I should be using to do that...

[regehr]

Rebase.

[regehr]

rebase

include/llvm/Analysis/LazyValueInfo.h

 namespace llvm {
   class AssumptionCache;
   class Constant;
+  class ConstantRange;
   class DataLayout;
   class DominatorTree;
   class Instruction;

   /// 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

   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,