Add support for DW_TAG_thrown_type.

For Swift we would like to be able to encode the error types that a
function may throw, so the debugger can display them alongside the
function's return value when finish-ing a function.

DWARF defines DW_TAG_thrown_type (intended to be used for C++ throw()
declarations) that is a perfect fit for this purpose. This patch wires
up support for DW_TAG_thrown_type in LLVM by adding a list of thrown
types to DISubprogram.

To offset the cost of the extra pointer, there is a follow-up patch
that turns DISubprogram into a variable-length node.

rdar://problem/29481673

Differential Revision: https://reviews.llvm.org/D32559

llvm-svn: 301489

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -1608,6 +1608,7 @@ void ModuleBitcodeWriter::writeDISubprogram(const DISubprogram *N,
   Record.push_back(VE.getMetadataOrNullID(N->getDeclaration()));
   Record.push_back(VE.getMetadataOrNullID(N->getVariables().get()));
   Record.push_back(N->getThisAdjustment());
+  Record.push_back(VE.getMetadataOrNullID(N->getThrownTypes().get()));
 
   Stream.EmitRecord(bitc::METADATA_SUBPROGRAM, Record, Abbrev);
   Record.clear();