[Bitcode][Asm] Parse metadata value from operand bundles

Support parsing operand bundles with metadata value from LLVM IR.

This is almost an NFC since there is no existing producers/consumers for
metadata operand bundle values, except the following call graph section
patches in revision:

Producer: https://reviews.llvm.org/D105909?id=358327
Consumer: https://reviews.llvm.org/D105915?id=358335

The test in this revision only ensures that the parser does not
complain. The above-mentioned patches implicity test if passed metadata
value is correct.

Reviewed By:
morehouse

Differential Revision: https://reviews.llvm.org/D107038?id=362649

Pull Request: llvm#87570

Author: necipfazil

llvm/lib/AsmParser/LLParser.cpp

@@ -3135,9 +3135,21 @@ bool LLParser::parseOptionalOperandBundles(
         return true;
 
       Type *Ty = nullptr;
-      Value *Input = nullptr;
-      if (parseType(Ty) || parseValue(Ty, Input, PFS))
+      if (parseType(Ty))
         return true;
+
+      Value *Input = nullptr;
+      // FIXME: Metadata operand bundle value is garbage when LLVM IR is
+      // compiled to bitcode, then disassembled back to LLVM IR. See D107039
+      // for the reproducers, and https://bugs.llvm.org/show_bug.cgi?id=51264
+      // for the bug report.
+      if (Ty->isMetadataTy()) {
+        if (parseMetadataAsValue(Input, PFS))
+          return true;
+      } else {
+        if (parseValue(Ty, Input, PFS))
+          return true;
+      }
       Inputs.push_back(Input);
     }
 

llvm/test/Bitcode/2021-07-22-Parse-Metadata-Operand-Bundles.ll

@@ -0,0 +1,9 @@
+; This test ensures that we parse metadata operand bundle values.
+; RUN: llvm-as < %s
+
+declare void @callee()
+
+define void @call_with_operand_bundle() {
+  call void @callee() [ "op_type"(metadata !"metadata_string") ]
+  ret void
+}