IR: Add assembly/bitcode support for function metadata attachments

Add serialization support for function metadata attachments (added in
r235783).  The syntax is:

    define @foo() !attach !0 {

Metadata attachments are only allowed on functions with bodies.  Since
they come before the `{`, they're not really part of the body; since
they require a body, they're not really part of the header.  In
`LLParser` I gave them a separate function called from `ParseDefine()`,
`ParseOptionalFunctionMetadata()`.

In bitcode, I'm using the same `METADATA_ATTACHMENT` record used by
instructions.  Instruction metadata attachments are included in a
special "attachment" block at the end of a `Function`.  The attachment
records are laid out like this:

    InstID (KindID MetadataID)+

Note that these records always have an odd number of fields.  The new
code takes advantage of this to recognize function attachments (which
don't need an instruction ID):

    (KindID MetadataID)+

This means we can use the same attachment block already used for
instructions.

This is part of PR23340.

llvm-svn: 235785

1 files changed, 10 insertions, 1 deletions

diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 52a5d48..b8baabd 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -1279,6 +1279,15 @@ static void WriteMetadataAttachment(const Function &F,
   // Write metadata attachments
   // METADATA_ATTACHMENT - [m x [value, [n x [id, mdnode]]]
   SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
+  F.getAllMetadata(MDs);
+  if (!MDs.empty()) {
+    for (const auto &I : MDs) {
+      Record.push_back(I.first);
+      Record.push_back(VE.getMetadataID(I.second));
+    }
+    Stream.EmitRecord(bitc::METADATA_ATTACHMENT, Record, 0);
+    Record.clear();
+  }
 
   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
@@ -2091,7 +2100,7 @@ static void WriteFunction(const Function &F, ValueEnumerator &VE,
   // Keep a running idea of what the instruction ID is.
   unsigned InstID = CstEnd;
 
-  bool NeedsMetadataAttachment = false;
+  bool NeedsMetadataAttachment = F.hasMetadata();
 
   MDLocation *LastDL = nullptr;