Add initial implementation of basic block tracing runtime

llvm-svn: 13339

runtime/libprofile/BasicBlockTracing.c

@@ -0,0 +1,67 @@
+/*===-- BasicBlockTracing.c - Support library for basic block tracing -----===*\
+|*
+|*                     The LLVM Compiler Infrastructure
+|*
+|* This file was developed by the LLVM research group and is distributed under
+|* the University of Illinois Open Source License. See LICENSE.TXT for details.
+|* 
+|*===----------------------------------------------------------------------===*|
+|* 
+|* This file implements the call back routines for the basic block tracing
+|* instrumentation pass.  This should be used with the -trace-basic-blocks
+|* LLVM pass.
+|*
+\*===----------------------------------------------------------------------===*/
+
+#include "Profiling.h"
+#include <stdlib.h>
+#include <stdio.h>
+
+static unsigned *ArrayStart, *ArrayEnd, *ArrayCursor;
+
+/* WriteAndFlushBBTraceData - write out the currently accumulated trace data
+ * and reset the cursor to point to the beginning of the buffer.
+ */
+static void WriteAndFlushBBTraceData () {
+  write_profiling_data(BBTrace, ArrayStart, (ArrayCursor - ArrayStart));
+  ArrayCursor = ArrayStart;
+}
+
+/* BBTraceAtExitHandler - When the program exits, just write out any remaining 
+ * data and free the trace buffer.
+ */
+static void BBTraceAtExitHandler() {
+  WriteAndFlushBBTraceData ();
+  free (ArrayStart);
+}
+
+/* llvm_trace_basic_block - called upon hitting a new basic block. */
+void llvm_trace_basic_block (unsigned BBNum) {
+  *ArrayCursor++ = BBNum;
+  if (ArrayCursor == ArrayEnd)
+    WriteAndFlushBBTraceData ();
+}
+
+/* llvm_start_basic_block_tracing - This is the main entry point of the basic
+ * block tracing library.  It is responsible for setting up the atexit
+ * handler and allocating the trace buffer.
+ */
+int llvm_start_basic_block_tracing(int argc, const char **argv,
+                              unsigned *arrayStart, unsigned numElements) {
+  int Ret;
+  const unsigned BufferSize = 128 * 1024;
+  unsigned ArraySize;
+
+  Ret = save_arguments(argc, argv);
+
+  /* Allocate a buffer to contain BB tracing data */
+  ArraySize = BufferSize / sizeof (unsigned);
+  ArrayStart = malloc (ArraySize * sizeof (unsigned));
+  ArrayEnd = ArrayStart + ArraySize;
+  ArrayCursor = ArrayStart;
+
+  /* Set up the atexit handler. */
+  atexit (BBTraceAtExitHandler);
+
+  return Ret;
+}