[Profile] compiler-rt support for setting profile output from command line

[tejohnson]

Summary

This change is the first of 3 patches to add support for specifying
the profile output from the command line via -fprofile-instr-generate=<path>,
where the specified output path/file will be overridden by the
LLVM_PROFILE_FILE environment variable.

Several changes are made to the runtime to support this:

1. Add a new interface __llvm_profile_set_filename_env_override that will

set the profile output filename, but allows the LLVM_PROFILE_FILE to override.
This is the interface used by the new option.

2. Refactor the pid-expansion done for LLVM_PROFILE_FILE into a separate

routine that can be shared by the various filename setting routines
(so that the filename from the option can also use the "%p" syntax).

3. Move the truncation into setFilename, and only truncate if there is a

new filename specified (to maintain support for appending to the same
profile file in the case of multiple shared objects built with profiling).

4. Move the handling for a NULL filename passed to __llvm_profile_setfilename*

into the new setFilenamePossiblyWithPid routine. The handling for a null
LLVM_PROFILE_FILE (which should not reset) is done by caller
setFilenameFromEnvironment.

[davidxl]

lib/profile/InstrProfiling.h

92

Is it better to merge this interface with the previous one but with an additional parameter ?

lib/profile/InstrProfilingFile.c

187–188

The behavior of this interface changes (improves) slightly. Is this intended?

[tejohnson]

lib/profile/InstrProfiling.h

92

I didn't want to affect any existing users of the __llvm_profile_set_filename interface by adding a new parameter (since this is C not C++ and can't add parameter defaults).

lib/profile/InstrProfilingFile.c

187–188

Yes. I am guessing that the lack of %p handling in the existing __llvm_profile_set_filename was probably just because no one needed it.

[tejohnson]

Re: [Profile] compiler-rt support for setting profile output from command line

Updated patch based on comments from Justin:

• Passing NULL to the filename setting interfaces now resets to default.profraw as

indicated in the header file description.

• Changed a couple of routine names to be clearer.
• New tests.

[tejohnson]

Adding a link to Justin's LGTM since it didn't show up here:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20150427/273749.html

Committed as r236055 and r236056.

[tejohnson]

Marking accepted since it was LGTM'ed and committed.

[tejohnson]

Committed awhile back as r236055 and r236056, closing manually.

lib/profile/InstrProfiling.h

 uint64_t *__llvm_profile_begin_counters(void);
 uint64_t *__llvm_profile_end_counters(void);
 
 /*!
  * \brief Write instrumentation data to the current file.
  *
  * Writes to the file with the last name given to \a __llvm_profile_set_filename(),
  * or if it hasn't been called, the \c LLVM_PROFILE_FILE environment variable,
- * or if that's not set, \c "default.profdata".
+ * or if that's not set, the last name given to
+ * \a __llvm_profile_override_default_filename(), or if that's not set,
+ * \c "default.profdata".
  */
 int __llvm_profile_write_file(void);
 
 /*!
  * \brief Set the filename for writing instrumentation data.
  *
  * Sets the filename to be used for subsequent calls to
  * \a __llvm_profile_write_file().
  *
  * \c Name is not copied, so it must remain valid.  Passing NULL resets the
  * filename logic to the default behaviour.
  */
 void __llvm_profile_set_filename(const char *Name);
 
+/*!
+ * \brief Set the filename for writing instrumentation data, unless the
+ * \c LLVM_PROFILE_FILE environment variable was set.
+ *
+ * Unless overridden, sets the filename to be used for subsequent calls to
+ * \a __llvm_profile_write_file().
+ *
+ * \c Name is not copied, so it must remain valid.  Passing NULL resets the
+ * filename logic to the default behaviour (unless the \c LLVM_PROFILE_FILE
+ * was set in which case it has no effect).
+ */
+void __llvm_profile_override_default_filename(const char *Name);
+
 /*! \brief Register to write instrumentation data to file at exit. */
 int __llvm_profile_register_write_file_atexit(void);
 
 /*! \brief Initialize file handling. */
 void __llvm_profile_initialize_file(void);
 
 /*! \brief Get the magic token for the file format. */
 uint64_t __llvm_profile_get_magic(void);
 
 /*! \brief Get the version of the file format. */
 uint64_t __llvm_profile_get_version(void);
 
 #endif /* PROFILE_INSTRPROFILING_H_ */

lib/profile/InstrProfilingFile.c

static int writeFileWithName(const char *OutputName) {
 
   fclose(OutputFile);
   return RetVal;
 }
 
 __attribute__((weak)) int __llvm_profile_OwnsFilename = 0;
 __attribute__((weak)) const char *__llvm_profile_CurrentFilename = NULL;
 
-static void setFilename(const char *Filename, int OwnsFilename) {
-  if (__llvm_profile_OwnsFilename)
-    free(UNCONST(__llvm_profile_CurrentFilename));
-
-  __llvm_profile_CurrentFilename = Filename;
-  __llvm_profile_OwnsFilename = OwnsFilename;
-}
-
 static void truncateCurrentFile(void) {
   const char *Filename;
   FILE *File;
 
   Filename = __llvm_profile_CurrentFilename;
   if (!Filename || !Filename[0])
     return;
 
   /* Truncate the file.  Later we'll reopen and append. */
   File = fopen(Filename, "w");
   if (!File)
     return;
   fclose(File);
 }
 
-static void setDefaultFilename(void) { setFilename("default.profraw", 0); }
+static void setFilename(const char *Filename, int OwnsFilename) {
+  /* Check if this is a new filename and therefore needs truncation. */
+  int NewFile = !__llvm_profile_CurrentFilename ||
+      (Filename && strcmp(Filename, __llvm_profile_CurrentFilename));
+  if (__llvm_profile_OwnsFilename)
+    free(UNCONST(__llvm_profile_CurrentFilename));
+
+  __llvm_profile_CurrentFilename = Filename;
+  __llvm_profile_OwnsFilename = OwnsFilename;
+
+  /* If not a new file, append to support profiling multiple shared objects. */
+  if (NewFile)
+    truncateCurrentFile();
+}
+
+static void resetFilenameToDefault(void) { setFilename("default.profraw", 0); }
 
 int getpid(void);
-static int setFilenameFromEnvironment(void) {
-  const char *Filename = getenv("LLVM_PROFILE_FILE");
+static int setFilenamePossiblyWithPid(const char *Filename) {
 #define MAX_PID_SIZE 16
   char PidChars[MAX_PID_SIZE] = {0};
   int NumPids = 0, PidLength = 0;
   char *Allocated;
   int I, J;
 
-  if (!Filename || !Filename[0])
-    return -1;
+  /* Reset filename on NULL, except with env var which is checked by caller. */
+  if (!Filename) {
+    resetFilenameToDefault();
+    return 0;
+  }
 
   /* Check the filename for "%p", which indicates a pid-substitution. */
   for (I = 0; Filename[I]; ++I)
     if (Filename[I] == '%' && Filename[++I] == 'p')
       if (!NumPids++) {
         PidLength = snprintf(PidChars, MAX_PID_SIZE, "%d", getpid());
         if (PidLength <= 0)
           return -1;
if (Filename[I] == '%') {
       Allocated[J++] = Filename[I];
   Allocated[J] = 0;
 
   /* Use the computed name. */
   setFilename(Allocated, 1);
   return 0;
 }
 
+static int setFilenameFromEnvironment(void) {
+  const char *Filename = getenv("LLVM_PROFILE_FILE");
+
+  if (!Filename || !Filename[0])
+    return -1;
+
+  return setFilenamePossiblyWithPid(Filename);
+}
+
 static void setFilenameAutomatically(void) {
   if (!setFilenameFromEnvironment())
     return;
 
-  setDefaultFilename();
+  resetFilenameToDefault();
 }
 
 __attribute__((visibility("hidden")))
 void __llvm_profile_initialize_file(void) {
   /* Check if the filename has been initialized. */
   if (__llvm_profile_CurrentFilename)
     return;
 
   /* Detect the filename and truncate. */
   setFilenameAutomatically();
-  truncateCurrentFile();
 }
 
 __attribute__((visibility("hidden")))
 void __llvm_profile_set_filename(const char *Filename) {
-  setFilename(Filename, 0);
-  truncateCurrentFile();
+  setFilenamePossiblyWithPid(Filename);
+}
+
+__attribute__((visibility("hidden")))
+void __llvm_profile_override_default_filename(const char *Filename) {
+  /* If the env var is set, skip setting filename from argument. */
+  const char *Env_Filename = getenv("LLVM_PROFILE_FILE");
+  if (Env_Filename && Env_Filename[0])
+    return;
+  setFilenamePossiblyWithPid(Filename);
 }
 
 __attribute__((visibility("hidden")))
 int __llvm_profile_write_file(void) {
   int rc;
 
   /* Check the filename. */
   if (!__llvm_profile_CurrentFilename)

test/profile/instrprof-override-filename-then-reset-default.c

+// RUN: %clang_profgen -o %t -O3 %s
+// RUN: %run %t %t.profraw
+// RUN: llvm-profdata merge -o %t.profdata default.profraw
+// RUN: %clang_profuse=%t.profdata -o - -S -emit-llvm %s | FileCheck %s
+
+void __llvm_profile_override_default_filename(const char *);
+int main(int argc, const char *argv[]) {
+  // CHECK: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}, !prof ![[PD1:[0-9]+]]
+  if (argc < 2)
+    return 1;
+  __llvm_profile_override_default_filename(argv[1]);
+  __llvm_profile_override_default_filename(0);
+  return 0;
+}
+// CHECK: ![[PD1]] = !{!"branch_weights", i32 1, i32 2}

test/profile/instrprof-override-filename-with-env.c

+// RUN: %clang_profgen -o %t -O3 %s
+// RUN: env LLVM_PROFILE_FILE=%t.good.profraw %run %t %t.bad.profraw
+// RUN: llvm-profdata merge -o %t.profdata %t.good.profraw
+// RUN: %clang_profuse=%t.profdata -o - -S -emit-llvm %s | FileCheck %s
+
+void __llvm_profile_override_default_filename(const char *);
+int main(int argc, const char *argv[]) {
+  // CHECK: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}, !prof ![[PD1:[0-9]+]]
+  if (argc < 2)
+    return 1;
+  __llvm_profile_override_default_filename(argv[1]);
+  return 0;
+}
+// CHECK: ![[PD1]] = !{!"branch_weights", i32 1, i32 2}

test/profile/instrprof-override-filename.c

+// RUN: %clang_profgen -o %t -O3 %s
+// RUN: %run %t %t.profraw
+// RUN: llvm-profdata merge -o %t.profdata %t.profraw
+// RUN: %clang_profuse=%t.profdata -o - -S -emit-llvm %s | FileCheck %s
+
+void __llvm_profile_override_default_filename(const char *);
+int main(int argc, const char *argv[]) {
+  // CHECK: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}, !prof ![[PD1:[0-9]+]]
+  if (argc < 2)
+    return 1;
+  __llvm_profile_override_default_filename(argv[1]);
+  return 0;
+}
+// CHECK: ![[PD1]] = !{!"branch_weights", i32 1, i32 2}

test/profile/instrprof-set-filename-then-reset-default.c

+// RUN: %clang_profgen -o %t -O3 %s
+// RUN: %run %t %t.profraw
+// RUN: llvm-profdata merge -o %t.profdata default.profraw
+// RUN: %clang_profuse=%t.profdata -o - -S -emit-llvm %s | FileCheck %s
+
+void __llvm_profile_set_filename(const char *);
+int main(int argc, const char *argv[]) {
+  // CHECK: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}, !prof ![[PD1:[0-9]+]]
+  if (argc < 2)
+    return 1;
+  __llvm_profile_set_filename(argv[1]);
+  __llvm_profile_set_filename(0);
+  return 0;
+}
+// CHECK: ![[PD1]] = !{!"branch_weights", i32 1, i32 2}