Implement Function::getIntrinsicID without it needing to call Value::getName,
which allocates a string.  This speeds up instcombine on 447.dealII by 5%.

llvm-svn: 34318
diff --git a/llvm/lib/VMCore/Function.cpp b/llvm/lib/VMCore/Function.cpp
index fcbf73f..8aa0caa 100644
--- a/llvm/lib/VMCore/Function.cpp
+++ b/llvm/lib/VMCore/Function.cpp
@@ -160,12 +160,15 @@
 /// llvm/Intrinsics.h.
 ///
 unsigned Function::getIntrinsicID() const {
-  const std::string& Name = this->getName();
-  if (Name.size() < 5 || Name[4] != '.' || Name[0] != 'l' || Name[1] != 'l'
+  const ValueName *ValName = this->getValueName();
+  unsigned Len = ValName->getKeyLength();
+  const char *Name = ValName->getKeyData();
+  
+  if (Len < 5 || Name[4] != '.' || Name[0] != 'l' || Name[1] != 'l'
       || Name[2] != 'v' || Name[3] != 'm')
     return 0;  // All intrinsics start with 'llvm.'
 
-  assert(Name.size() != 5 && "'llvm.' is an invalid intrinsic name!");
+  assert(Len != 5 && "'llvm.' is an invalid intrinsic name!");
 
 #define GET_FUNCTION_RECOGNIZER
 #include "llvm/Intrinsics.gen"