Add a JITEventListener interface that gets called back when a new function is

emitted or the machine code for a function is freed.  Chris mentioned that we
may also want a notification when a stub is emitted, but that'll be a future
change.  I intend to use this to tell oprofile where functions are emitted and
what lines correspond to what addresses.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74157 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 173 insertions, 0 deletions

diff --git a/lib/ExecutionEngine/JIT/MacOSJITEventListener.cpp b/lib/ExecutionEngine/JIT/MacOSJITEventListener.cpp
new file mode 100644
index 0000000000..3b8b84ce5b
--- /dev/null
+++ b/lib/ExecutionEngine/JIT/MacOSJITEventListener.cpp
@@ -0,0 +1,173 @@
+//===-- MacOSJITEventListener.cpp - Save symbol table for OSX perf tools --===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a JITEventListener object that records JITted functions to
+// a global __jitSymbolTable linked list.  Apple's performance tools use this to
+// determine a symbol name and accurate code range for a PC value.  Because
+// performance tools are generally asynchronous, the code below is written with
+// the hope that it could be interrupted at any time and have useful answers.
+// However, we don't go crazy with atomic operations, we just do a "reasonable
+// effort".
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "macos-jit-event-listener"
+#include "llvm/Function.h"
+#include "llvm/ExecutionEngine/JITEventListener.h"
+#include <stddef.h>
+using namespace llvm;
+
+#ifdef __APPLE__
+#define ENABLE_JIT_SYMBOL_TABLE 0
+#endif
+
+#if ENABLE_JIT_SYMBOL_TABLE
+
+namespace {
+
+/// JITSymbolEntry - Each function that is JIT compiled results in one of these
+/// being added to an array of symbols.  This indicates the name of the function
+/// as well as the address range it occupies.  This allows the client to map
+/// from a PC value to the name of the function.
+struct JITSymbolEntry {
+  const char *FnName;   // FnName - a strdup'd string.
+  void *FnStart;
+  intptr_t FnSize;
+};
+
+
+struct JITSymbolTable {
+  /// NextPtr - This forms a linked list of JitSymbolTable entries.  This
+  /// pointer is not used right now, but might be used in the future.  Consider
+  /// it reserved for future use.
+  JITSymbolTable *NextPtr;
+  
+  /// Symbols - This is an array of JitSymbolEntry entries.  Only the first
+  /// 'NumSymbols' symbols are valid.
+  JITSymbolEntry *Symbols;
+  
+  /// NumSymbols - This indicates the number entries in the Symbols array that
+  /// are valid.
+  unsigned NumSymbols;
+  
+  /// NumAllocated - This indicates the amount of space we have in the Symbols
+  /// array.  This is a private field that should not be read by external tools.
+  unsigned NumAllocated;
+};
+
+class MacOSJITEventListener : public JITEventListener {
+public:
+  virtual void NotifyFunctionEmitted(const Function &F,
+                                     void *FnStart, size_t FnSize,
+                                     const EmittedFunctionDetails &Details);
+  virtual void NotifyFreeingMachineCode(const Function &F, void *OldPtr);
+};
+
+}  // anonymous namespace.
+
+// This is a public symbol so the performance tools can find it.
+JITSymbolTable *__jitSymbolTable;
+
+namespace llvm {
+JITEventListener *createMacOSJITEventListener() {
+  return new MacOSJITEventListener;
+}
+}
+
+// Adds the just-emitted function to the symbol table.
+void MacOSJITEventListener::NotifyFunctionEmitted(
+    const Function &F, void *FnStart, size_t FnSize,
+    const EmittedFunctionDetails &) {
+  const char *const FnName = F.getNameStart();
+  assert(FnName != 0 && FnStart != 0 && "Bad symbol to add");
+  JITSymbolTable **SymTabPtrPtr = 0;
+  SymTabPtrPtr = &__jitSymbolTable;
+
+  // If this is the first entry in the symbol table, add the JITSymbolTable
+  // index.
+  if (*SymTabPtrPtr == 0) {
+    JITSymbolTable *New = new JITSymbolTable();
+    New->NextPtr = 0;
+    New->Symbols = 0;
+    New->NumSymbols = 0;
+    New->NumAllocated = 0;
+    *SymTabPtrPtr = New;
+  }
+
+  JITSymbolTable *SymTabPtr = *SymTabPtrPtr;
+
+  // If we have space in the table, reallocate the table.
+  if (SymTabPtr->NumSymbols >= SymTabPtr->NumAllocated) {
+    // If we don't have space, reallocate the table.
+    unsigned NewSize = std::max(64U, SymTabPtr->NumAllocated*2);
+    JITSymbolEntry *NewSymbols = new JITSymbolEntry[NewSize];
+    JITSymbolEntry *OldSymbols = SymTabPtr->Symbols;
+
+    // Copy the old entries over.
+    memcpy(NewSymbols, OldSymbols, SymTabPtr->NumSymbols*sizeof(OldSymbols[0]));
+
+    // Swap the new symbols in, delete the old ones.
+    SymTabPtr->Symbols = NewSymbols;
+    SymTabPtr->NumAllocated = NewSize;
+    delete [] OldSymbols;
+  }
+
+  // Otherwise, we have enough space, just tack it onto the end of the array.
+  JITSymbolEntry &Entry = SymTabPtr->Symbols[SymTabPtr->NumSymbols];
+  Entry.FnName = strdup(FnName);
+  Entry.FnStart = FnStart;
+  Entry.FnSize = FnSize;
+  ++SymTabPtr->NumSymbols;
+}
+
+// Removes the to-be-deleted function from the symbol table.
+void MacOSJITEventListener::NotifyFreeingMachineCode(
+    const Function &, void *FnStart) {
+  assert(FnStart && "Invalid function pointer");
+  JITSymbolTable **SymTabPtrPtr = 0;
+  SymTabPtrPtr = &__jitSymbolTable;
+
+  JITSymbolTable *SymTabPtr = *SymTabPtrPtr;
+  JITSymbolEntry *Symbols = SymTabPtr->Symbols;
+
+  // Scan the table to find its index.  The table is not sorted, so do a linear
+  // scan.
+  unsigned Index;
+  for (Index = 0; Symbols[Index].FnStart != FnStart; ++Index)
+    assert(Index != SymTabPtr->NumSymbols && "Didn't find function!");
+
+  // Once we have an index, we know to nuke this entry, overwrite it with the
+  // entry at the end of the array, making the last entry redundant.
+  const char *OldName = Symbols[Index].FnName;
+  Symbols[Index] = Symbols[SymTabPtr->NumSymbols-1];
+  free((void*)OldName);
+
+  // Drop the number of symbols in the table.
+  --SymTabPtr->NumSymbols;
+
+  // Finally, if we deleted the final symbol, deallocate the table itself.
+  if (SymTabPtr->NumSymbols != 0)
+    return;
+
+  *SymTabPtrPtr = 0;
+  delete [] Symbols;
+  delete SymTabPtr;
+}
+
+#else  // !ENABLE_JIT_SYMBOL_TABLE
+
+namespace llvm {
+// By defining this to return NULL, we can let clients call it unconditionally,
+// even if they aren't on an Apple system.
+JITEventListener *createMacOSJITEventListener() {
+  return NULL;
+}
+}  // namespace llvm
+
+#endif  // ENABLE_JIT_SYMBOL_TABLE