commit a29aac7b774d1fec7033f6d0fdfaf919e97e8492
author Adrian Prantl <aprantl@apple.com> Fri Jan 05 01:13:37 2018 +0000
committer Adrian Prantl <aprantl@apple.com> Fri Jan 05 01:13:37 2018 +0000
tree 5e587194de1e42c151a402551dd4539375bb90be
parent 0429ebfabc4275a0f4cc120bb69e2ea317af3cfa

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

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 911e462..8a9d95c 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -975,6 +975,15 @@
         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:

llvm/lib/IR/Verifier.cpp

diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 1754f7d..ab93b85 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -905,9 +905,12 @@
   }
 }
 
+/// Detect mutually exclusive flags.
 static bool hasConflictingReferenceFlags(unsigned Flags) {
-  return (Flags & DINode::FlagLValueReference) &&
-         (Flags & DINode::FlagRValueReference);
+  return ((Flags & DINode::FlagLValueReference) &&
+          (Flags & DINode::FlagRValueReference)) ||
+         ((Flags & DINode::FlagTypePassByValue) &&
+          (Flags & DINode::FlagTypePassByReference));
 }
 
 void Verifier::visitTemplateParams(const MDNode &N, const Metadata &RawParams) {