Speed up Function::isIntrinsic() by adding a bit to GlobalValue. NFC

Summary:
Previously isIntrinsic() called getName().  This involves a hashtable
lookup, so is nontrivially expensive.  And isIntrinsic() is called
frequently, particularly by dyn_cast<IntrinsicInstr>.

This patch steals a bit of IntID and uses that to store whether or not
getName() starts with "llvm."

Reviewers: bogner, arsenm, joker-eph

Subscribers: sanjoy, llvm-commits

Differential Revision: https://reviews.llvm.org/D22949

llvm-svn: 290691

1 files changed, 6 insertions, 3 deletions

diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
index b87c85e44a8..05419aa3d2b 100644
--- a/llvm/lib/IR/Function.cpp
+++ b/llvm/lib/IR/Function.cpp
@@ -270,6 +270,7 @@ Function::Function(FunctionType *Ty, LinkageTypes Linkage, const Twine &name,
   if (ParentModule)
     ParentModule->getFunctionList().push_back(this);
 
+  HasLLVMReservedName = getName().startswith("llvm.");
   // Ensure intrinsics have the right parameter attributes.
   // Note, the IntID field will have been set in Value::setName if this function
   // name is a valid intrinsic ID.
@@ -500,12 +501,14 @@ Intrinsic::ID Function::lookupIntrinsicID(StringRef Name) {
 }
 
 void Function::recalculateIntrinsicID() {
-  const ValueName *ValName = this->getValueName();
-  if (!ValName || !isIntrinsic()) {
+  StringRef Name = getName();
+  if (!Name.startswith("llvm.")) {
+    HasLLVMReservedName = false;
     IntID = Intrinsic::not_intrinsic;
     return;
   }
-  IntID = lookupIntrinsicID(ValName->getKey());
+  HasLLVMReservedName = true;
+  IntID = lookupIntrinsicID(Name);
 }
 
 /// Returns a stable mangling for the type specified for use in the name