[YAMLIO] Add the ability to map with context.

mapping a yaml field to an object in code has always been
a stateless operation.  You could still pass state by using the
`setContext` function of the YAMLIO object, but this represented
global state for the entire yaml input.  In order to have
context-sensitive state, it is necessary to pass this state in
at the granularity of an individual mapping.

This patch adds support for this type of context-sensitive state.
You simply pass an additional argument of type T to the
`mapRequired` or `mapOptional` functions, and provided you have
specialized a `MappingContextTraits<U, T>` class with the
appropriate mapping function, you can pass this context into
the mapping function.

Reviewed By: chandlerc
Differential Revision: https://reviews.llvm.org/D24162

llvm-svn: 280977

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MIRParser/MIRParser.cpp b/llvm/lib/CodeGen/MIRParser/MIRParser.cpp
index 6dae8b84d37..9a36405bce9 100644
--- a/llvm/lib/CodeGen/MIRParser/MIRParser.cpp
+++ b/llvm/lib/CodeGen/MIRParser/MIRParser.cpp
@@ -257,7 +257,8 @@ std::unique_ptr<Module> MIRParserImpl::parse() {
 bool MIRParserImpl::parseMachineFunction(yaml::Input &In, Module &M,
                                          bool NoLLVMIR) {
   auto MF = llvm::make_unique<yaml::MachineFunction>();
-  yaml::yamlize(In, *MF, false);
+  yaml::EmptyContext Ctx;
+  yaml::yamlize(In, *MF, false, Ctx);
   if (In.error())
     return true;
   auto FunctionName = MF->Name;