[tablegen] Avoid creating a temporary vector in getInstructionCase

Record::getValues returns ArrayRef which has a cast operator
to std::vector, as a result a temporary vector is created
if the type of the variable is const std::vector& 
that was suboptimal in this case.

Differential revision: https://reviews.llvm.org/D34969

Test plan: make check-all

llvm-svn: 307059

llvm/include/llvm/ProfileData/InstrProf.h

@@ -753,11 +753,8 @@ uint32_t InstrProfRecord::getNumValueKinds() const {
 
 uint32_t InstrProfRecord::getNumValueData(uint32_t ValueKind) const {
   uint32_t N = 0;
-  const std::vector<InstrProfValueSiteRecord> &SiteRecords =
-      getValueSitesForKind(ValueKind);
-  for (auto &SR : SiteRecords) {
+  for (auto &SR : getValueSitesForKind(ValueKind))
     N += SR.ValueData.size();
-  }
   return N;
 }