DebugInfo: support for DWARFv5 DW_AT_alignment attribute

* Assume that clang passes non-zero alignment value to DIBuilder
only in case when it was forced by C++11 'alignas', C11 '_Alignas'
or compiler attribute '__attribute__((aligned (N)))'.

* Emit DW_AT_alignment if alignment is specified for type/object.

Differential Revision: https://reviews.llvm.org/D24425

llvm-svn: 285189

2 files changed, 24 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 025e69354d1..9345fac2a99 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -118,6 +118,10 @@ DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(
   else
     addGlobalName(GV->getName(), *VariableDIE, DeclContext);
 
+  if (uint32_t AlignInBytes = GV->getAlignInBytes())
+    addUInt(*VariableDIE, dwarf::DW_AT_alignment, dwarf::DW_FORM_udata,
+            AlignInBytes);
+
   // Add location.
   bool addToAccelTable = false;
 
@@ -771,7 +775,13 @@ void DwarfCompileUnit::applyVariableAttributes(const DbgVariable &Var,
   StringRef Name = Var.getName();
   if (!Name.empty())
     addString(VariableDie, dwarf::DW_AT_name, Name);
-  addSourceLine(VariableDie, Var.getVariable());
+  const auto *DIVar = Var.getVariable();
+  if (DIVar)
+    if (uint32_t AlignInBytes = DIVar->getAlignInBytes())
+      addUInt(VariableDie, dwarf::DW_AT_alignment, dwarf::DW_FORM_udata,
+              AlignInBytes);
+
+  addSourceLine(VariableDie, DIVar);
   addType(VariableDie, Var.getType());
   if (Var.isArtificial())
     addFlag(VariableDie, dwarf::DW_AT_artificial);
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index bec554dcdf0..d3b84de9eb5 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1007,6 +1007,11 @@ void DwarfUnit::constructTypeDIE(DIE &Buffer, const DICompositeType *CTy) {
     if (RLang)
       addUInt(Buffer, dwarf::DW_AT_APPLE_runtime_class, dwarf::DW_FORM_data1,
               RLang);
+
+    // Add align info if available.
+    if (uint64_t AlignInBytes = CTy->getAlignInBytes())
+      addUInt(Buffer, dwarf::DW_AT_alignment, dwarf::DW_FORM_udata,
+              AlignInBytes);
   }
 }
 
@@ -1394,6 +1399,7 @@ void DwarfUnit::constructMemberDIE(DIE &Buffer, const DIDerivedType *DT) {
   } else {
     uint64_t Size = DT->getSizeInBits();
     uint64_t FieldSize = DD->getBaseTypeSize(DT);
+    uint64_t AlignInBytes = DT->getAlignInBytes();
     uint64_t OffsetInBytes;
 
     bool IsBitfield = FieldSize && Size != FieldSize;
@@ -1431,6 +1437,9 @@ void DwarfUnit::constructMemberDIE(DIE &Buffer, const DIDerivedType *DT) {
     } else {
       // This is not a bitfield.
       OffsetInBytes = DT->getOffsetInBits() / 8;
+      if (AlignInBytes)
+        addUInt(MemberDie, dwarf::DW_AT_alignment, dwarf::DW_FORM_udata,
+                AlignInBytes);
     }
 
     if (DD->getDwarfVersion() <= 2) {
@@ -1507,6 +1516,10 @@ DIE *DwarfUnit::getOrCreateStaticMemberDIE(const DIDerivedType *DT) {
   if (const ConstantFP *CFP = dyn_cast_or_null<ConstantFP>(DT->getConstant()))
     addConstantFPValue(StaticMemberDIE, CFP);
 
+  if (uint64_t AlignInBytes = DT->getAlignInBytes())
+    addUInt(StaticMemberDIE, dwarf::DW_AT_alignment, dwarf::DW_FORM_udata,
+            AlignInBytes);
+
   return &StaticMemberDIE;
 }