[profile] Make atexit hook a no-op on Fuchsia

On Fuchsia, we always use the continuous mode with runtime counter
relocation, so there's no need for atexit hook or support for dumping
the profile manually.

Differential Revision: https://reviews.llvm.org/D76556

compiler-rt/lib/profile/InstrProfiling.h

@@ -218,6 +218,9 @@ int __llvm_profile_register_write_file_atexit(void);
 /*! \brief Initialize file handling. */
 void __llvm_profile_initialize_file(void);
 
+/*! \brief Initialize the profile runtime. */
+void __llvm_profile_initialize(void);
+
 /*!
  * \brief Return path prefix (excluding the base filename) of the profile data.
  * This is useful for users using \c -fprofile-generate=./path_prefix who do

compiler-rt/lib/profile/InstrProfilingBuffer.c

@@ -10,9 +10,6 @@
 #include "InstrProfilingInternal.h"
 #include "InstrProfilingPort.h"
 
-/* When counters are being relocated at runtime, this parameter is set to 1. */
-COMPILER_RT_VISIBILITY int RuntimeCounterRelocation = 0;
-
 /* When continuous mode is enabled (%c), this parameter is set to 1.
  *
  * This parameter is defined here in InstrProfilingBuffer.o, instead of in
@@ -66,7 +63,7 @@ void __llvm_profile_get_padding_sizes_for_counters(
     uint64_t *PaddingBytesBeforeCounters, uint64_t *PaddingBytesAfterCounters,
     uint64_t *PaddingBytesAfterNames) {
   if (!__llvm_profile_is_continuous_mode_enabled() ||
-      RuntimeCounterRelocation) {
+      lprofRuntimeCounterRelocation()) {
     *PaddingBytesBeforeCounters = 0;
     *PaddingBytesAfterCounters = 0;
     *PaddingBytesAfterNames = __llvm_profile_get_num_padding_bytes(NamesSize);

compiler-rt/lib/profile/InstrProfilingFile.c

@@ -35,6 +35,16 @@
 #include "InstrProfilingPort.h"
 #include "InstrProfilingUtil.h"
 
+static int RuntimeCounterRelocation = 0;
+
+COMPILER_RT_VISIBILITY unsigned lprofRuntimeCounterRelocation(void) {
+  return RuntimeCounterRelocation;
+}
+
+COMPILER_RT_VISIBILITY void lprofSetRuntimeCounterRelocation(void) {
+  RuntimeCounterRelocation = 1;
+}
+
 /* From where is profile name specified.
  * The order the enumerators define their
  * precedence. Re-order them may lead to
@@ -477,7 +487,8 @@ static int writeMMappedFile(FILE *OutputFile, char **Profile) {
 }
 
 static void relocateCounters(void) {
-  if (!__llvm_profile_is_continuous_mode_enabled() || !RuntimeCounterRelocation)
+  if (!__llvm_profile_is_continuous_mode_enabled() ||
+      !lprofRuntimeCounterRelocation())
     return;
 
   /* Get the sizes of various profile data sections. Taken from
@@ -808,7 +819,7 @@ static void parseAndSetFilename(const char *FilenamePat,
 
   truncateCurrentFile();
   if (__llvm_profile_is_continuous_mode_enabled()) {
-    if (RuntimeCounterRelocation)
+    if (lprofRuntimeCounterRelocation())
       relocateCounters();
     else
       initializeProfileForContinuousMode();
@@ -951,10 +962,10 @@ const char *__llvm_profile_get_filename(void) {
   return FilenameBuf;
 }
 
-/* This method is invoked by the runtime initialization hook
- * InstrProfilingRuntime.o if it is linked in. Both user specified
+/* This API initializes the file handling, both user specified
  * profile path via -fprofile-instr-generate= and LLVM_PROFILE_FILE
- * environment variable can override this default value. */
+ * environment variable can override this default value.
+ */
 COMPILER_RT_VISIBILITY
 void __llvm_profile_initialize_file(void) {
   const char *EnvFilenamePat;
@@ -963,7 +974,7 @@ void __llvm_profile_initialize_file(void) {
   int hasCommandLineOverrider = (INSTR_PROF_PROFILE_NAME_VAR[0] != 0);
 
   if (__llvm_profile_counter_bias != -1)
-    RuntimeCounterRelocation = 1;
+    lprofSetRuntimeCounterRelocation();
 
   EnvFilenamePat = getFilenamePatFromEnv();
   if (EnvFilenamePat) {
@@ -982,6 +993,16 @@ void __llvm_profile_initialize_file(void) {
   parseAndSetFilename(SelectedPat, PNS, 0);
 }
 
+/* This method is invoked by the runtime initialization hook
+ * InstrProfilingRuntime.o if it is linked in.
+ */
+COMPILER_RT_VISIBILITY
+void __llvm_profile_initialize(void) {
+  __llvm_profile_initialize_file();
+  if (!__llvm_profile_is_continuous_mode_enabled())
+    __llvm_profile_register_write_file_atexit();
+}
+
 /* 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/lib/profile/InstrProfilingInternal.h

@@ -184,7 +184,10 @@ uint64_t lprofGetLoadModuleSignature();
 unsigned lprofProfileDumped();
 void lprofSetProfileDumped();
 
-COMPILER_RT_VISIBILITY extern int RuntimeCounterRelocation;
+/* Return non zero value if counters are being relocated at runtime. */
+unsigned lprofRuntimeCounterRelocation(void);
+void lprofSetRuntimeCounterRelocation(void);
+
 COMPILER_RT_VISIBILITY extern void (*FreeHook)(void *);
 COMPILER_RT_VISIBILITY extern uint8_t *DynamicBufferIOBuffer;
 COMPILER_RT_VISIBILITY extern uint32_t VPBufferSize;

compiler-rt/lib/profile/InstrProfilingPlatformFuchsia.c

@@ -34,7 +34,11 @@
 #include "InstrProfilingInternal.h"
 #include "InstrProfilingUtil.h"
 
-/* VMO that contains the coverage data shared across all modules. */
+COMPILER_RT_VISIBILITY unsigned lprofRuntimeCounterRelocation(void) {
+  return 1;
+}
+
+/* VMO that contains the profile data for this module. */
 static zx_handle_t __llvm_profile_vmo;
 /* Current offset within the VMO where data should be written next. */
 static uint64_t __llvm_profile_offset;
@@ -92,43 +96,23 @@ static void initVMOWriter(ProfDataWriter *This) {
   This->WriterCtx = NULL;
 }
 
-static int dump(void) {
-  if (lprofProfileDumped()) {
-    lprofWrite("LLVM Profile: data not published: already written.\n");
-    return 0;
-  }
-
-  /* Check if there is llvm/runtime version mismatch. */
-  if (GET_VERSION(__llvm_profile_get_version()) != INSTR_PROF_RAW_VERSION) {
-    lprofWrite("LLVM Profile: runtime and instrumentation version mismatch: "
-               "expected %d, but got %d\n",
-               INSTR_PROF_RAW_VERSION,
-               (int)GET_VERSION(__llvm_profile_get_version()));
-    return -1;
-  }
-
-  /* Write the profile data into the mapped region. */
-  ProfDataWriter VMOWriter;
-  initVMOWriter(&VMOWriter);
-  if (lprofWriteData(&VMOWriter, lprofGetVPDataReader(), 0) != 0)
-    return -1;
-
-  return 0;
-}
-
+/* This method is invoked by the runtime initialization hook
+ * InstrProfilingRuntime.o if it is linked in. */
 COMPILER_RT_VISIBILITY
-int __llvm_profile_dump(void) {
-  int rc = dump();
-  lprofSetProfileDumped();
-  return rc;
-}
-
-static void dumpWithoutReturn(void) { dump(); }
-
-static void createVMO(void) {
-  /* Don't create VMO if it has been alread created. */
-  if (__llvm_profile_vmo != ZX_HANDLE_INVALID)
+void __llvm_profile_initialize(void) {
+  /* This symbol is defined as weak and initialized to -1 by the runtimer, but
+   * compiler will generate a strong definition initialized to 0 when runtime
+   * counter relocation is used. */
+  if (__llvm_profile_counter_bias == -1) {
+    lprofWrite("LLVM Profile: counter relocation at runtime is required\n");
     return;
+  }
+
+  /* Don't create VMO if it has been alread created. */
+  if (__llvm_profile_vmo != ZX_HANDLE_INVALID) {
+    lprofWrite("LLVM Profile: VMO has already been created\n");
+    return;
+  }
 
   const __llvm_profile_data *DataBegin = __llvm_profile_begin_data();
   const __llvm_profile_data *DataEnd = __llvm_profile_end_data();
@@ -211,23 +195,4 @@ static void createVMO(void) {
       (uintptr_t)__llvm_profile_begin_counters() + CountersOffset;
 }
 
-/* This method is invoked by the runtime initialization hook
- * InstrProfilingRuntime.o if it is linked in.
- */
-COMPILER_RT_VISIBILITY
-void __llvm_profile_initialize_file(void) { createVMO(); }
-
-COMPILER_RT_VISIBILITY
-int __llvm_profile_register_write_file_atexit(void) {
-  static bool HasBeenRegistered = false;
-
-  if (HasBeenRegistered)
-    return 0;
-
-  lprofSetupValueProfiler();
-
-  HasBeenRegistered = true;
-  return atexit(dumpWithoutReturn);
-}
-
 #endif

compiler-rt/lib/profile/InstrProfilingRuntime.cpp

@@ -19,9 +19,7 @@ namespace {
 class RegisterRuntime {
 public:
   RegisterRuntime() {
-    __llvm_profile_initialize_file();
-    if (!__llvm_profile_is_continuous_mode_enabled())
-      __llvm_profile_register_write_file_atexit();
+    __llvm_profile_initialize();
   }
 };