llvm · efriedma-quic · Nov 14, 2025 · Nov 17, 2025
diff --git a/compiler-rt/CMakeLists.txt b/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)
 
 #================================

diff --git a/compiler-rt/lib/profile/CMakeLists.txt b/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

diff --git a/compiler-rt/lib/profile/InstrProfiling.c b/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"

diff --git a/compiler-rt/lib/profile/InstrProfiling.h b/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);

diff --git a/compiler-rt/lib/profile/InstrProfilingMerge.c b/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;
   }
 

diff --git a/compiler-rt/lib/profile/InstrProfilingMergeFile.c b/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"

diff --git a/compiler-rt/lib/profile/InstrProfilingPlatformLinux.c b/compiler-rt/lib/profile/InstrProfilingPlatformLinux.c
@@ -6,16 +6,33 @@
 |*
 \*===----------------------------------------------------------------------===*/
 
+// This file defines profile data symbols for ELF, wasm, XCOFF. It assumes
+// __start_ and __stop_ symbols for profile data point at the beginning and
+// end of the sections in question.  (This is technically a linker feature,
+// not a file format feature, but linkers for these targets support it.)
+//
+// MachO (MacOS/iOS) and PE-COFF (Windows) have a similar support, but the
+// identifiers are different, so the support is in separate files.
+//
+// Support for targets which don't have linker support is in
+// InstrProfilingPlatformOther.c.
+//
+// This file also contains code to extract ELF build IDs from the ELF file,
+// to identify the build which generated the file.
+
 #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)
 
-#if !defined(_AIX) && !defined(__wasm__)
+#if !defined(_AIX) && !defined(__wasm__) &&                                    \
+    !defined(COMPILER_RT_PROFILE_BAREMETAL)
+// Includes for non-baremetal ELF targets, used to output build IDs.
 #include <elf.h>
 #include <link.h>
-#endif
 #include <stdlib.h>
 #include <string.h>
+#endif
 
 #include "InstrProfiling.h"
 #include "InstrProfilingInternal.h"

diff --git a/compiler-rt/lib/profile/InstrProfilingPlatformOther.c b/compiler-rt/lib/profile/InstrProfilingPlatformOther.c
@@ -6,10 +6,18 @@
 |*
 \*===----------------------------------------------------------------------===*/
 
+// This file defines a fallback implementation to compute the locations of
+// profile data sections, for targets that don't have linker support.  No
+// commonly used targets use this codepath.
+//
+// This implementation expects the compiler instrumentation pass to define a
+// constructor in each file which calls into this file.
+
 #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>

diff --git a/compiler-rt/lib/profile/InstrProfilingPort.h b/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_ */