Debug Info: Support DW_AT_calling_convention on composite types.

This implements the DWARF 5 feature described at
http://www.dwarfstd.org/ShowIssue.php?issue=141215.1

This allows a consumer to understand whether a composite data type is
trivially copyable and thus should be passed by value instead of by
reference. The canonical example is being able to distinguish the
following two types:

  // S is not trivially copyable because of the explicit destructor.
  struct S {
     ~S() {}
  };

  // T is a POD type.
  struct T {
     ~T() = default;
  };

This patch adds two new (DI)flags to LLVM metadata: TypePassByValue
and TypePassByReference.

<rdar://problem/36034922>
Differential Revision: https://reviews.llvm.org/D41743

llvm-svn: 321844

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 911e4623578..8a9d95c1e04 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -975,6 +975,15 @@ void DwarfUnit::constructTypeDIE(DIE &Buffer, const DICompositeType *CTy) {
         Tag == dwarf::DW_TAG_structure_type || Tag == dwarf::DW_TAG_union_type)
       addTemplateParams(Buffer, CTy->getTemplateParams());
 
+    // Add the type's non-standard calling convention.
+    uint8_t CC = 0;
+    if (CTy->isTypePassByValue())
+      CC = dwarf::DW_CC_pass_by_value;
+    else if (CTy->isTypePassByReference())
+      CC = dwarf::DW_CC_pass_by_reference;
+    if (CC)
+      addUInt(Buffer, dwarf::DW_AT_calling_convention, dwarf::DW_FORM_data1,
+              CC);
     break;
   }
   default: