Rename isPowerOfTwo to isKnownToBeAPowerOfTwo.

In a previous thread it was pointed out that isPowerOfTwo is not a very precise
name since it can return false for powers of two if it is unable to show that
they are powers of two.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170093 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 019596c..b95da85 100644
--- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -37,7 +37,7 @@
   if (match(V, m_LShr(m_OneUse(m_Shl(m_Value(PowerOf2), m_Value(A))),
                       m_Value(B))) &&
       // The "1" can be any value known to be a power of 2.
-      isPowerOfTwo(PowerOf2)) {
+      isKnownToBeAPowerOfTwo(PowerOf2)) {
     A = IC.Builder->CreateSub(A, B);
     return IC.Builder->CreateShl(PowerOf2, A);
   }
@@ -45,7 +45,7 @@
   // (PowerOfTwo >>u B) --> isExact since shifting out the result would make it
   // inexact.  Similarly for <<.
   if (BinaryOperator *I = dyn_cast<BinaryOperator>(V))
-    if (I->isLogicalShift() && isPowerOfTwo(I->getOperand(0))) {
+    if (I->isLogicalShift() && isKnownToBeAPowerOfTwo(I->getOperand(0))) {
       // We know that this is an exact/nuw shift and that the input is a
       // non-zero context as well.
       if (Value *V2 = simplifyValueKnownNonZero(I->getOperand(0), IC)) {