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

2 files changed, 13 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 16fb20dd7e2..f2e13992883 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -662,6 +662,14 @@ void DwarfUnit::addTemplateParams(DIE &Buffer, DINodeArray TParams) {
   }
 }
 
+/// Add thrown types.
+void DwarfUnit::addThrownTypes(DIE &Die, DINodeArray ThrownTypes) {
+  for (const auto *Ty : ThrownTypes) {
+    DIE &TT = createAndAddDIE(dwarf::DW_TAG_thrown_type, Die);
+    addType(TT, cast<DIType>(Ty));
+  }
+}
+
 DIE *DwarfUnit::getOrCreateContextDIE(const DIScope *Context) {
   if (!Context || isa<DIFile>(Context))
     return &getUnitDie();
@@ -1249,6 +1257,8 @@ void DwarfUnit::applySubprogramAttributes(const DISubprogram *SP, DIE &SPDie,
     constructSubprogramArguments(SPDie, Args);
   }
 
+  addThrownTypes(SPDie, SP->getThrownTypes());
+
   if (SP->isArtificial())
     addFlag(SPDie, dwarf::DW_AT_artificial);
 
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
index e84df465088..3bf4979030a 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
@@ -230,6 +230,9 @@ public:
   /// Add template parameters in buffer.
   void addTemplateParams(DIE &Buffer, DINodeArray TParams);
 
+  /// Add thrown types.
+  void addThrownTypes(DIE &Die, DINodeArray ThrownTypes);
+
   // FIXME: Should be reformulated in terms of addComplexAddress.
   /// Start with the address based on the location provided, and generate the
   /// DWARF information necessary to find the actual Block variable (navigating