Adding a collector name attribute to Function in the IR. These

methods are new to Function:

  bool hasCollector() const;
  const std::string &getCollector() const;
  void setCollector(const std::string &);
  void clearCollector();

The assembly representation is as such:

  define void @f() gc "shadow-stack" { ...

The implementation uses an on-the-side table to map Functions to 
collector names, such that there is no overhead. A StringPool is 
further used to unique collector names, which are extremely
likely to be unique per process.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44769 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 39 insertions, 0 deletions

diff --git a/lib/VMCore/Function.cpp b/lib/VMCore/Function.cpp
index 04db3aa..18effea 100644
--- a/lib/VMCore/Function.cpp
+++ b/lib/VMCore/Function.cpp
@@ -17,8 +17,10 @@
 #include "llvm/CodeGen/ValueTypes.h"
 #include "llvm/Support/LeakDetector.h"
 #include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/StringPool.h"
 #include "SymbolTableListTraitsImpl.h"
 #include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/StringExtras.h"
 using namespace llvm;
 
@@ -297,6 +299,9 @@ Function::~Function() {
   // Drop our reference to the parameter attributes, if any.
   if (ParamAttrs)
     ParamAttrs->dropRef();
+  
+  // Remove the function from the on-the-side collector table.
+  clearCollector();
 }
 
 void Function::BuildLazyArguments() const {
@@ -379,6 +384,40 @@ void Function::dropAllReferences() {
   BasicBlocks.clear();    // Delete all basic blocks...
 }
 
+// Maintain the collector name for each function in an on-the-side table. This
+// saves allocating an additional word in Function for programs which do not use
+// GC (i.e., most programs) at the cost of increased overhead for clients which
+// do use GC.
+static DenseMap<const Function*,PooledStringPtr> *CollectorNames;
+static StringPool *CollectorNamePool;
+
+bool Function::hasCollector() const {
+  return CollectorNames && CollectorNames->count(this);
+}
+
+const char *Function::getCollector() const {
+  assert(hasCollector() && "Function has no collector");
+  return *(*CollectorNames)[this];
+}
+
+void Function::setCollector(const char *Str) {
+  if (!CollectorNamePool)
+    CollectorNamePool = new StringPool();
+  if (!CollectorNames)
+    CollectorNames = new DenseMap<const Function*,PooledStringPtr>();
+  (*CollectorNames)[this] = CollectorNamePool->intern(Str);
+}
+
+void Function::clearCollector() {
+  if (CollectorNames) {
+    CollectorNames->erase(this);
+    if (CollectorNames->empty()) {
+      delete CollectorNames;
+      CollectorNames = 0;
+    }
+  }
+}
+
 /// getIntrinsicID - This method returns the ID number of the specified
 /// function, or Intrinsic::not_intrinsic if the function is not an
 /// intrinsic, or if the pointer is null.  This value is always defined to be