[llvm] r311400 - [ValueTracking] Add assertions that the starting Depth in isKnownToBeAPowerOfTwo and ComputeNumSignBitsImpl is not above MaxDepth

[Craig Topper via llvm-commits]

Author: ctopper
Date: Mon Aug 21 15:56:12 2017
New Revision: 311400

URL: http://llvm.org/viewvc/llvm-project?rev=311400&view=rev
Log:
[ValueTracking] Add assertions that the starting Depth in isKnownToBeAPowerOfTwo and ComputeNumSignBitsImpl is not above MaxDepth

The function does an equality check later to terminate the recursion, but that won't work if its starts out too high. Similar assert already exists in computeKnownBits.

Modified:
    llvm/trunk/lib/Analysis/ValueTracking.cpp

Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=311400&r1=311399&r2=311400&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Mon Aug 21 15:56:12 2017
@@ -1562,6 +1562,8 @@ void computeKnownBits(const Value *V, Kn
 /// types and vectors of integers.
 bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
                             const Query &Q) {
+  assert(Depth <= MaxDepth && "Limit Search Depth");
+
   if (const Constant *C = dyn_cast<Constant>(V)) {
     if (C->isNullValue())
       return OrZero;
@@ -2021,6 +2023,7 @@ static unsigned ComputeNumSignBits(const
 /// vector element with the mininum number of known sign bits.
 static unsigned ComputeNumSignBitsImpl(const Value *V, unsigned Depth,
                                        const Query &Q) {
+  assert(Depth <= MaxDepth && "Limit Search Depth");
 
   // We return the minimum number of sign bits that are guaranteed to be present
   // in V, so for undef we have to conservatively return 1.  We don't have the