[APInt] Rename getSignBit to getSignMask

getSignBit is a static function that creates an APInt with only the sign bit set. getSignMask seems like a better name to convey its functionality. In fact several places use it and then store in an APInt named SignMask.

Differential Revision: https://reviews.llvm.org/D32108

llvm-svn: 300856
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index bca3435..2259fba 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -568,11 +568,11 @@
       match(Op1, m_Not(m_Specific(Op0))))
     return Constant::getAllOnesValue(Ty);
 
-  // add nsw/nuw (xor Y, signbit), signbit --> Y
+  // add nsw/nuw (xor Y, signmask), signmask --> Y
   // The no-wrapping add guarantees that the top bit will be set by the add.
   // Therefore, the xor must be clearing the already set sign bit of Y.
-  if ((isNSW || isNUW) && match(Op1, m_SignBit()) &&
-      match(Op0, m_Xor(m_Value(Y), m_SignBit())))
+  if ((isNSW || isNUW) && match(Op1, m_SignMask()) &&
+      match(Op0, m_Xor(m_Value(Y), m_SignMask())))
     return Y;
 
   /// i1 add -> xor.
@@ -2819,7 +2819,7 @@
             return ConstantInt::getTrue(RHS->getContext());
         }
       }
-      if (CIVal->isSignBit() && *CI2Val == 1) {
+      if (CIVal->isSignMask() && *CI2Val == 1) {
         if (Pred == ICmpInst::ICMP_UGT)
           return ConstantInt::getFalse(RHS->getContext());
         if (Pred == ICmpInst::ICMP_ULE)