[compiler-rt] 6bc9c8d - [compiler-rt][profile] Add padding after binary IDs

[Leonard Chan via llvm-commits]

Author: Leonard Chan
Date: 2021-09-23T10:29:24-07:00
New Revision: 6bc9c8dfe32cc4662f2ed9041af527f69dfff13b

URL: https://github.com/llvm/llvm-project/commit/6bc9c8dfe32cc4662f2ed9041af527f69dfff13b
DIFF: https://github.com/llvm/llvm-project/commit/6bc9c8dfe32cc4662f2ed9041af527f69dfff13b.diff

LOG: [compiler-rt][profile] Add padding after binary IDs

Some tests with binary IDs would fail with error: no profile can be merged.
This is because raw profiles could have unaligned headers when emitting binary
IDs. This means padding should be emitted after binary IDs are emitted to
ensure everything else is aligned. This patch accounts for that padding in
__llvm_write_binary_ids.

Differential Revision: https://reviews.llvm.org/D110188

Added: 
    

Modified: 
    compiler-rt/lib/profile/InstrProfilingPlatformLinux.c

Removed: 
    


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diff  --git a/compiler-rt/lib/profile/InstrProfilingPlatformLinux.c b/compiler-rt/lib/profile/InstrProfilingPlatformLinux.c
index 5d47083b8bfe7..03cbd3312df4b 100644
--- a/compiler-rt/lib/profile/InstrProfilingPlatformLinux.c
+++ b/compiler-rt/lib/profile/InstrProfilingPlatformLinux.c
@@ -142,7 +142,9 @@ static int WriteBinaryIdForNote(ProfDataWriter *Writer,
 
 /*
  * Helper function that iterates through notes section and find build ids.
- * If writer is given, write binary ids into profiles.
+ * If writer is given, write binary ids into profiles. This also takes into
+ * account padding which may need to be added after the binary IDs to ensure
+ * 8-byte alignment.
  * If an error happens while writing, return -1.
  */
 static int WriteBinaryIds(ProfDataWriter *Writer, const ElfW(Nhdr) * Note,
@@ -160,7 +162,17 @@ static int WriteBinaryIds(ProfDataWriter *Writer, const ElfW(Nhdr) * Note,
     Note = (const ElfW(Nhdr) *)((const char *)(Note) + NoteOffset);
   }
 
-  return TotalBinaryIdsSize;
+  uint8_t BinaryIdsPadding =
+      __llvm_profile_get_num_padding_bytes(TotalBinaryIdsSize);
+  if (Writer) {
+    ProfDataIOVec BinaryIdIOVec[] = {
+        {NULL, sizeof(uint8_t), BinaryIdsPadding, 1}};
+    if (Writer->Write(Writer, BinaryIdIOVec,
+                      sizeof(BinaryIdIOVec) / sizeof(*BinaryIdIOVec)))
+      return -1;
+  }
+
+  return TotalBinaryIdsSize + BinaryIdsPadding;
 }
 
 /*