From 7dcadc6dbe42a91cd88804a5994eab987b42c753 Mon Sep 17 00:00:00 2001
From: Manman Ren <mren@apple.com>
Date: Fri, 2 Nov 2012 01:10:15 +0000
Subject: [PATCH] PGO: allows the profile data file name to be specified by the
 LLVMPROF_OUTPUT environment variable.

This allows parallel make for profiling code, without it there are file
collisions as each parallel run uses the default file name.

There is already code in the runtime library to specify the output file name
via the command line, but this only works for programs which already process
argc/argv.  This patch builds on that support.

Patch by Alastair Murray.

llvm-svn: 167269
---
 llvm/runtime/libprofile/CommonProfiling.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/llvm/runtime/libprofile/CommonProfiling.c b/llvm/runtime/libprofile/CommonProfiling.c
index acc17ce..058270b 100644
--- a/llvm/runtime/libprofile/CommonProfiling.c
+++ b/llvm/runtime/libprofile/CommonProfiling.c
@@ -28,14 +28,35 @@
 
 static char *SavedArgs = 0;
 static unsigned SavedArgsLength = 0;
+static const char *SavedEnvVar = 0;
 
 static const char *OutputFilename = "llvmprof.out";
 
+/* check_environment_variable - Check to see if the LLVMPROF_OUTPUT environment
+ * variable is set.  If it is then save it and set OutputFilename.
+ */
+static void check_environment_variable(void) {
+  if (SavedEnvVar) return; /* Guarantee that we can't leak memory. */
+
+  const char *EnvVar = getenv("LLVMPROF_OUTPUT");
+  if (EnvVar) {
+    /* The string that getenv returns is allowed to be statically allocated,
+     * which means it may be changed by future calls to getenv, so copy it.
+     */
+    SavedEnvVar = strdup(EnvVar);
+    OutputFilename = SavedEnvVar;
+  }
+}
+
 /* save_arguments - Save argc and argv as passed into the program for the file
  * we output.
+ * If either the LLVMPROF_OUTPUT environment variable or the -llvmprof-output
+ * command line argument are set then change OutputFilename to the provided
+ * value.  The command line argument value overrides the environment variable.
  */
 int save_arguments(int argc, const char **argv) {
   unsigned Length, i;
+  if (!SavedEnvVar && !SavedArgs) check_environment_variable();
   if (SavedArgs || !argv) return argc;  /* This can be called multiple times */
 
   /* Check to see if there are any arguments passed into the program for the
@@ -54,6 +75,7 @@ int save_arguments(int argc, const char **argv) {
         puts("-llvmprof-output requires a filename argument!");
       else {
         OutputFilename = strdup(argv[1]);
+        if (SavedEnvVar) { free((void *)SavedEnvVar); SavedEnvVar = 0; }
         memmove((char**)&argv[1], &argv[2], (argc-1)*sizeof(char*));
         --argc;
       }
-- 
2.7.4