[PGO] Add support for profile dumping dir relocation

[davidxl]

Summary

This patch adds support in profile runtime to allow user change the root directory of the profile. It uses a machanism compatible to libgcc: GCOV_PREFIX and GCOV_PREFIX_STRIP.

It also helps users to easily migrate to use LLVM PGO.

[vsk]

Lgtm, although I think the line-wrapping on the added RUN lines needs to be corrected.

[xur]

Lgtm.

lib/profile/InstrProfilingFile.c

524

Nit: the call is sunk to the branch, why not getting rid of SelectPat and PNS variable?
Also to the third calls.

[davidxl]

Addressed review feedback.

lib/profile/InstrProfilingFile.c

 
 /* This method is invoked by the runtime initialization hook
  * InstrProfilingRuntime.o if it is linked in. Both user specified
  * profile path via -fprofile-instr-generate= and LLVM_PROFILE_FILE
  * environment variable can override this default value. */
 COMPILER_RT_VISIBILITY
 void __llvm_profile_initialize_file(void) {
   const char *EnvFilenamePat;
-  const char *SelectedPat = NULL;
-  ProfileNameSpecifier PNS = PNS_unknown;
   int hasCommandLineOverrider = (INSTR_PROF_PROFILE_NAME_VAR[0] != 0);
 
   EnvFilenamePat = getFilenamePatFromEnv();
-  if (EnvFilenamePat) {
-    SelectedPat = EnvFilenamePat;
-    PNS = PNS_environment;
-  } else if (hasCommandLineOverrider) {
-    SelectedPat = INSTR_PROF_PROFILE_NAME_VAR;
-    PNS = PNS_command_line;
+  if (EnvFilenamePat)
+    parseAndSetFilename(EnvFilenamePat, PNS_environment, 0);
+  else if (hasCommandLineOverrider) {
+    const char *SelectedPat = INSTR_PROF_PROFILE_NAME_VAR;
+
+    size_t PrefixLen;
+    int StripLen;
+    const char *Prefix = lprofGetPathPrefix(&StripLen, &PrefixLen);
+    if (Prefix != NULL) {
+      char *StripPat =
+          COMPILER_RT_ALLOCA(PrefixLen + 1 + strlen(SelectedPat) + 1);
+      lprofApplyPathPrefix(StripPat, SelectedPat, Prefix, PrefixLen, StripLen);
+      SelectedPat = StripPat;
+    }
+
+    parseAndSetFilename(SelectedPat, PNS_command_line, Prefix ? 1 : 0);
   } else {
-    SelectedPat = NULL;
-    PNS = PNS_default;
+    parseAndSetFilename(NULL, PNS_default, 0);
   }
 
-  parseAndSetFilename(SelectedPat, PNS, 0);
 }
 
 /* This API is directly called by the user application code. It has the
  * highest precedence compared with LLVM_PROFILE_FILE environment variable
  * and command line option -fprofile-instr-generate=<profile_name>.
  */
 COMPILER_RT_VISIBILITY
 void __llvm_profile_set_filename(const char *FilenamePat) {

lib/profile/InstrProfilingUtil.c

       continue;
 
     StrippedPathStr = Ptr;
     ++Level;
   }
 
   memcpy(Dest, Prefix, PrefixLen);
 
-  if (!IS_DIR_SEPARATOR(Prefix[PrefixLen - 1]))
+  if (!IS_DIR_SEPARATOR(Prefix[PrefixLen - 1]) &&
+      !IS_DIR_SEPARATOR(StrippedPathStr[0]))
     Dest[PrefixLen++] = DIR_SEPARATOR;
 
   memcpy(Dest + PrefixLen, StrippedPathStr, strlen(StrippedPathStr) + 1);
 }
 
 COMPILER_RT_VISIBILITY const char *
 lprofFindFirstDirSeparator(const char *Path) {
   const char *Sep;

test/profile/instrprof-path.c

 // RUN: %clang_pgogen -O2 -o %t.0 %s
 // RUN: %clang_pgogen=%t.d1 -O2 -o %t.1 %s
 // RUN: %clang_pgogen=%t.d1/%t.d2 -O2 -o %t.2 %s
+// RUN: %clang_pgogen=a/b/c/d -O2 -o %t.3 %s
+// RUN: %clang_pgogen=/a/b/c/d -O2 -o %t.4 %s
 //
 // RUN: %run %t.0  ""
 // RUN: env LLVM_PROFILE_FILE=%t.d1/default.profraw %run %t.0  %t.d1/
 // RUN: env LLVM_PROFILE_FILE=%t.d1/%t.d2/default.profraw %run %t.0 %t.d1/%t.d2/
 // RUN: %run %t.1 %t.d1/
 // RUN: %run %t.2 %t.d1/%t.d2/
 // RUN: %run %t.2 %t.d1/%t.d2/ %t.d1/%t.d2/%t.d3/blah.profraw %t.d1/%t.d2/%t.d3/
 
+// RUN: env GCOV_PREFIX=%t.prefix %run %t.3  %t.prefix/a/b/c/d/
+// RUN: env GCOV_PREFIX=%t.prefix env GCOV_PREFIX_STRIP=1 %run %t.3 %t.prefix/b/c/d/ 
+// RUN: env GCOV_PREFIX=%t.prefix env GCOV_PREFIX_STRIP=2 %run  %t.3  %t.prefix/c/d/ 
+// RUN: env GCOV_PREFIX=%t.prefix env GCOV_PREFIX_STRIP=3 %run %t.3  %t.prefix/d/
+
+// RUN: env GCOV_PREFIX=%t.prefix %run %t.4  %t.prefix/a/b/c/d/
+// RUN: env GCOV_PREFIX=%t.prefix env GCOV_PREFIX_STRIP=1 %run %t.4 %t.prefix/b/c/d/ 
+// RUN: env GCOV_PREFIX=%t.prefix env GCOV_PREFIX_STRIP=2 %run %t.4  %t.prefix/c/d/ 
+// RUN: env GCOV_PREFIX=%t.prefix env GCOV_PREFIX_STRIP=3 %run %t.4  %t.prefix/d/
+
+#include <stdio.h>
 #include <string.h>
 
 const char *__llvm_profile_get_path_prefix();
 void __llvm_profile_set_filanem(const char*);
 
 int main(int argc, const char *argv[]) {
   int i;
   const char *expected;
   const char *prefix;
   if (argc < 2)
     return 1;
 
   expected = argv[1];
   prefix = __llvm_profile_get_path_prefix();
 
-  if (strcmp(prefix, expected))
+  if (strcmp(prefix, expected)) {
+    fprintf(stderr, "Expected = %s\n", expected);
+    fprintf(stderr, "  Actual = %s\n", prefix);
     return 1;
+  }
 
   if (argc == 4) {
     __llvm_profile_set_filename(argv[2]);
     prefix = __llvm_profile_get_path_prefix();
     expected = argv[3];
     if (strcmp(prefix, expected))
       return 1;
   }
 
   return 0;
 }