[profile] Only use NT_GNU_BUILD_ID if supported

[ro]

Summary

The Solaris buildbots have been broken for some time by the unconditional use of
NT_GNU_BUILD_ID, e.g. Solaris/sparcv9 and Solaris/amd64. Being a GNU extension, it is not defined in <sys/elf.h>. However,
providing a fallback definition doesn't help because the code also relies on __ehdr_start,
another unportable GNU extension that most likely never will be implemented in
Solaris ld. Besides, there's reallly no point in supporting build ids since they aren't used
on Solaris at all.

This patch fixes this by make the relevant code conditional on the definition of
NT_GNU_BUILD_ID.

Tested on amd64-pc-solaris2.11 and sparcv9-sun-solaris2.11.

[gulfem]

compiler-rt/lib/profile/InstrProfilingPlatformLinux.c

192

Thanks for the fix! Could you please add the comment here like the simplified version of your commit message?

[ro]

Add comment.

[ro]

compiler-rt/lib/profile/InstrProfilingPlatformLinux.c

192

Sure, will commit as updated. Thanks.

compiler-rt/lib/profile/InstrProfilingPlatformLinux.c

__llvm_profile_begin_vnodes(void) {
   return &PROF_VNODES_START;
 }
 COMPILER_RT_VISIBILITY ValueProfNode *__llvm_profile_end_vnodes(void) {
   return &PROF_VNODES_STOP;
 }
 COMPILER_RT_VISIBILITY ValueProfNode *CurrentVNode = &PROF_VNODES_START;
 COMPILER_RT_VISIBILITY ValueProfNode *EndVNode = &PROF_VNODES_STOP;
 
+#ifdef NT_GNU_BUILD_ID
 static size_t RoundUp(size_t size, size_t align) {
   return (size + align - 1) & ~(align - 1);
 }
 
 /*
  * Write binary id length and then its data, because binary id does not
  * have a fixed length.
  */
const ElfW(Nhdr) *Note =
         (const ElfW(Nhdr) *)((uintptr_t)ElfHeader + ProgramHeader[I].p_offset);
     const ElfW(Nhdr) *NotesEnd =
         (const ElfW(Nhdr) *)((const char *)(Note) + ProgramHeader[I].p_filesz);
     return WriteBinaryIds(Writer, Note, NotesEnd);
   }
 
   return 0;
 }
+#else /* !NT_GNU_BUILD_ID */
+/*
+ * Fallback implementation for targets that don't support the GNU
+ * extensions NT_GNU_BUILD_ID and __ehdr_start.
+ */
+COMPILER_RT_VISIBILITY int __llvm_write_binary_ids(ProfDataWriter *Writer) {
+  return 0;
+}
+#endif
 
 #endif