[compiler-rt] Add baremetal version of profile library.

Adds a flag COMPILER_RT_PROFILE_BAREMETAL, which disables the parts of
the profile runtime which require a filesystem or malloc.  This minimal
library only requires string.h from the C library.

This is useful for profiling or code coverage of baremetal images, which
don't have filesystem APIs, and might not have malloc configured (or
have limited heap space).

There's some room for improvement here in the future for doing profiling
and code coverage for baremetal. If we revised the profiling format, and
introduced some additional host tooling, we could move some of the
metadata into non-allocated sections, and construct the profraw file on
the host.  But this patch is sufficient for some use-cases.

Author: efriedma-quic

compiler-rt/CMakeLists.txt

@@ -309,6 +309,8 @@ option(COMPILER_RT_USE_BUILTINS_LIBRARY
 
 option(COMPILER_RT_USE_ATOMIC_LIBRARY "Use compiler-rt atomic instead of libatomic" OFF)
 
+option(COMPILER_RT_PROFILE_BAREMETAL "Build minimal baremetal profile library" OFF)
+
 include(config-ix)
 
 #================================

compiler-rt/lib/profile/CMakeLists.txt

@@ -60,12 +60,9 @@ int main() {
 add_compiler_rt_component(profile)
 
 set(PROFILE_SOURCES
-  GCDAProfiling.c
   InstrProfiling.c
   InstrProfilingInternal.c
-  InstrProfilingValue.c
   InstrProfilingBuffer.c
-  InstrProfilingFile.c
   InstrProfilingMerge.c
   InstrProfilingMergeFile.c
   InstrProfilingNameVar.c
@@ -77,10 +74,25 @@ set(PROFILE_SOURCES
   InstrProfilingPlatformLinux.c
   InstrProfilingPlatformOther.c
   InstrProfilingPlatformWindows.c
-  InstrProfilingRuntime.cpp
-  InstrProfilingUtil.c
   )
 
+if (NOT COMPILER_RT_PROFILE_BAREMETAL)
+  # For baremetal, exclude the following:
+  # - Anything that contains filesystem operations (InstrProfilingFile.c,
+  #   InstrProfilingUtils.c)
+  # - Initialization, because it isn't necesary without the filesystem bits
+  #   on ELF targets (InstrProfilingRuntime.cpp).
+  # - Value profiling, because it requires malloc (InstrProfilingValue.c).
+  #   This could be optional if someone needs it.
+  # - GCDA profiling, which is unrelated (GCDAProfiling.c)
+  list(APPEND PROFILE_SOURCES GCDAProfiling.c
+                              InstrProfilingFile.c
+                              InstrProfilingRuntime.cpp
+                              InstrProfilingUtil.c
+                              InstrProfilingValue.c
+                              )
+endif()
+
 set(PROFILE_HEADERS
   InstrProfiling.h
   InstrProfilingInternal.h
@@ -135,6 +147,12 @@ if(COMPILER_RT_TARGET_HAS_UNAME)
      -DCOMPILER_RT_HAS_UNAME=1)
 endif()
 
+if(COMPILER_RT_PROFILE_BAREMETAL)
+ set(EXTRA_FLAGS
+     ${EXTRA_FLAGS}
+     -DCOMPILER_RT_PROFILE_BAREMETAL=1)
+endif()
+
 if(MSVC)
   # profile historically has only been supported with the static runtime
   # on windows

compiler-rt/lib/profile/InstrProfiling.c

@@ -10,8 +10,6 @@
 // with freestanding compilation. See `darwin_add_builtin_libraries`.
 
 #include <limits.h>
-#include <stdio.h>
-#include <stdlib.h>
 #include <string.h>
 
 #include "InstrProfiling.h"

compiler-rt/lib/profile/InstrProfiling.h

@@ -10,7 +10,10 @@
 #define PROFILE_INSTRPROFILING_H_
 
 #include "InstrProfilingPort.h"
+#include <stddef.h>
+#ifndef COMPILER_RT_PROFILE_BAREMETAL
 #include <stdio.h>
+#endif
 
 // Make sure __LLVM_INSTR_PROFILE_GENERATE is always defined before
 // including instr_prof_interface.h so the interface functions are
@@ -200,7 +203,9 @@ int __llvm_profile_write_file(void);
  * copying the old profile file to new profile file and this function is usually
  * used when the proess doesn't have permission to open file.
  */
+#ifndef COMPILER_RT_PROFILE_BAREMETAL
 int __llvm_profile_set_file_object(FILE *File, int EnableMerge);
+#endif
 
 /*! \brief Register to write instrumentation data to file at exit. */
 int __llvm_profile_register_write_file_atexit(void);

compiler-rt/lib/profile/InstrProfilingMerge.c

@@ -11,7 +11,6 @@
 
 #include "InstrProfiling.h"
 #include "InstrProfilingInternal.h"
-#include "InstrProfilingUtil.h"
 
 #define INSTR_PROF_VALUE_PROF_DATA
 #include "profile/InstrProfData.inc"
@@ -131,9 +130,11 @@ COMPILER_RT_VISIBILITY
 int __llvm_profile_merge_from_buffer(const char *ProfileData,
                                      uint64_t ProfileSize) {
   if (__llvm_profile_get_version() & VARIANT_MASK_TEMPORAL_PROF) {
+#ifndef COMPILER_RT_PROFILE_BAREMETAL
     PROF_ERR("%s\n",
              "Temporal profiles do not support profile merging at runtime. "
              "Instead, merge raw profiles using the llvm-profdata tool.");
+#endif
     return 1;
   }
 

compiler-rt/lib/profile/InstrProfilingMergeFile.c

@@ -13,7 +13,6 @@
 
 #include "InstrProfiling.h"
 #include "InstrProfilingInternal.h"
-#include "InstrProfilingUtil.h"
 
 #define INSTR_PROF_VALUE_PROF_DATA
 #include "profile/InstrProfData.inc"

compiler-rt/lib/profile/InstrProfilingPlatformLinux.c

@@ -8,14 +8,17 @@
 
 #if defined(__linux__) || defined(__FreeBSD__) || defined(__Fuchsia__) ||      \
     (defined(__sun__) && defined(__svr4__)) || defined(__NetBSD__) ||          \
-    defined(_AIX) || defined(__wasm__) || defined(__HAIKU__)
+    defined(_AIX) || defined(__wasm__) || defined(__HAIKU__) ||                \
+    defined(COMPILER_RT_PROFILE_BAREMETAL)
 
+#ifndef COMPILER_RT_PROFILE_BAREMETAL
 #if !defined(_AIX) && !defined(__wasm__)
 #include <elf.h>
 #include <link.h>
 #endif
 #include <stdlib.h>
 #include <string.h>
+#endif
 
 #include "InstrProfiling.h"
 #include "InstrProfilingInternal.h"

compiler-rt/lib/profile/InstrProfilingPlatformOther.c

@@ -9,7 +9,8 @@
 #if !defined(__APPLE__) && !defined(__linux__) && !defined(__FreeBSD__) &&     \
     !defined(__Fuchsia__) && !(defined(__sun__) && defined(__svr4__)) &&       \
     !defined(__NetBSD__) && !defined(_WIN32) && !defined(_AIX) &&              \
-    !defined(__wasm__) && !defined(__HAIKU__)
+    !defined(__wasm__) && !defined(__HAIKU__) &&                               \
+    !defined(COMPILER_RT_PROFILE_BAREMETAL)
 
 #include <stdlib.h>
 #include <stdio.h>

compiler-rt/lib/profile/InstrProfilingPort.h

@@ -117,7 +117,9 @@ static inline size_t getpagesize(void) {
   return S.dwPageSize;
 }
 #else /* defined(_WIN32) */
+#ifndef COMPILER_RT_PROFILE_BAREMETAL
 #include <unistd.h>
+#endif
 #endif /* defined(_WIN32) */
 
 #define PROF_ERR(Format, ...)                                                  \
@@ -137,16 +139,6 @@ static inline size_t getpagesize(void) {
 #define O_BINARY 0
 #endif
 
-#if defined(__FreeBSD__)
-
-#include <inttypes.h>
-#include <sys/types.h>
-
-#else /* defined(__FreeBSD__) */
-
-#include <inttypes.h>
 #include <stdint.h>
 
-#endif /* defined(__FreeBSD__) && defined(__i386__) */
-
 #endif /* PROFILE_INSTRPROFILING_PORT_H_ */