[CodeView] Properly align symbol records on read/write.

Object files have symbol records not aligned to any particular
boundary (e.g. 1-byte aligned), while PDB files have symbol
records padded to 4-byte aligned boundaries.  Since they share
the same reading / writing code, we have to provide an option to
specify the alignment and propagate it up to the producer or
consumer who knows what the alignment is supposed to be for the
given container type.

Added a test for this by modifying the existing PDB -> YAML -> PDB
round-tripping code to round trip symbol records as well as types.

Differential Revision: https://reviews.llvm.org/D33785

llvm-svn: 304484

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/DebugInfo/CodeView/CodeViewRecordIO.cpp b/llvm/lib/DebugInfo/CodeView/CodeViewRecordIO.cpp
index 282e3103adc..711144fc2fa 100644
--- a/llvm/lib/DebugInfo/CodeView/CodeViewRecordIO.cpp
+++ b/llvm/lib/DebugInfo/CodeView/CodeViewRecordIO.cpp
@@ -27,6 +27,14 @@ Error CodeViewRecordIO::beginRecord(Optional<uint32_t> MaxLength) {
 Error CodeViewRecordIO::endRecord() {
   assert(!Limits.empty() && "Not in a record!");
   Limits.pop_back();
+  // We would like to assert that we actually read / wrote all the bytes that we
+  // expected to for this record, but unfortunately we can't do this.  Some
+  // producers such as MASM over-allocate for certain types of records and
+  // commit the extraneous data, so when reading we can't be sure every byte
+  // will have been read.  And when writing we over-allocate temporarily since
+  // we don't know how big the record is until we're finished writing it, so
+  // even though we don't commit the extraneous data, we still can't guarantee
+  // we're at the end of the allocated data.
   return Error::success();
 }
 
@@ -49,6 +57,12 @@ uint32_t CodeViewRecordIO::maxFieldLength() const {
   return *Min;
 }
 
+Error CodeViewRecordIO::padToAlignment(uint32_t Align) {
+  if (isReading())
+    return Reader->padToAlignment(Align);
+  return Writer->padToAlignment(Align);
+}
+
 Error CodeViewRecordIO::skipPadding() {
   assert(!isWriting() && "Cannot skip padding while writing!");