Solidify the assumption that a DW_TAG_subprogram's type is a DW_TAG_subroutine_type

There were bits & pieces of code lying around that may've given the
impression that debug info metadata supported the possibility that a
subprogram's type could be specified by a non-subroutine type describing
the return type of a void function. This support was incomplete &
unnecessary. Asserts & API have been changed to make the desired usage
more clear.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182532 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/DIBuilder.h

@@ -505,7 +505,7 @@ namespace llvm {
     DISubprogram createFunction(DIDescriptor Scope, StringRef Name,
                                 StringRef LinkageName,
                                 DIFile File, unsigned LineNo,
-                                DIType Ty, bool isLocalToUnit,
+                                DICompositeType Ty, bool isLocalToUnit,
                                 bool isDefinition,
                                 unsigned ScopeLine,
                                 unsigned Flags = 0,
@@ -536,7 +536,7 @@ namespace llvm {
     DISubprogram createMethod(DIDescriptor Scope, StringRef Name,
                               StringRef LinkageName,
                               DIFile File, unsigned LineNo,
-                              DIType Ty, bool isLocalToUnit,
+                              DICompositeType Ty, bool isLocalToUnit,
                               bool isDefinition,
                               unsigned Virtuality = 0, unsigned VTableIndex = 0,
                               MDNode *VTableHolder = 0,

include/llvm/DebugInfo.h

@@ -427,19 +427,6 @@ namespace llvm {
     unsigned getLineNumber() const      { return getUnsignedField(6); }
     DICompositeType getType() const { return getFieldAs<DICompositeType>(7); }
 
-    /// getReturnTypeName - Subprogram return types are encoded either as
-    /// DIType or as DICompositeType.
-    StringRef getReturnTypeName() const {
-      DICompositeType DCT(getFieldAs<DICompositeType>(7));
-      if (DCT.Verify()) {
-        DIArray A = DCT.getTypeArray();
-        DIType T(A.getElement(0));
-        return T.getName();
-      }
-      DIType T(getFieldAs<DIType>(7));
-      return T.getName();
-    }
-
     /// isLocalToUnit - Return true if this subprogram is local to the current
     /// compile unit, like 'static' in C.
     unsigned isLocalToUnit() const     { return getUnsignedField(8); }

lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -1208,13 +1208,11 @@ DIE *CompileUnit::getOrCreateSubprogramDIE(DISubprogram SP) {
 
   // Add Return Type.
   DICompositeType SPTy = SP.getType();
-  DIArray Args = SPTy.getTypeArray();
+  assert(SPTy.getTag() == dwarf::DW_TAG_subroutine_type &&
-  unsigned SPTag = SPTy.getTag();
+         "the type of a subprogram should be a subroutine");
 
-  if (Args.getNumElements() == 0 || SPTag != dwarf::DW_TAG_subroutine_type)
+  DIArray Args = SPTy.getTypeArray();
-    addType(SPDie, SPTy);
+  addType(SPDie, DIType(Args.getElement(0)));
-  else
-    addType(SPDie, DIType(Args.getElement(0)));
 
   unsigned VK = SP.getVirtuality();
   if (VK) {
@@ -1232,19 +1230,14 @@ DIE *CompileUnit::getOrCreateSubprogramDIE(DISubprogram SP) {
 
     // Add arguments. Do not add arguments for subprogram definition. They will
     // be handled while processing variables.
-    DICompositeType SPTy = SP.getType();
+    for (unsigned i = 1, N =  Args.getNumElements(); i < N; ++i) {
-    DIArray Args = SPTy.getTypeArray();
+      DIE *Arg = new DIE(dwarf::DW_TAG_formal_parameter);
-    unsigned SPTag = SPTy.getTag();
+      DIType ATy = DIType(Args.getElement(i));
-
+      addType(Arg, ATy);
-    if (SPTag == dwarf::DW_TAG_subroutine_type)
+      if (ATy.isArtificial())
-      for (unsigned i = 1, N =  Args.getNumElements(); i < N; ++i) {
+        addFlag(Arg, dwarf::DW_AT_artificial);
-        DIE *Arg = new DIE(dwarf::DW_TAG_formal_parameter);
+      SPDie->addChild(Arg);
-        DIType ATy = DIType(Args.getElement(i));
+    }
-        addType(Arg, ATy);
-        if (ATy.isArtificial())
-          addFlag(Arg, dwarf::DW_AT_artificial);
-        SPDie->addChild(Arg);
-      }
   }
 
   if (SP.isArtificial())

lib/IR/DIBuilder.cpp

@@ -969,13 +969,15 @@ DISubprogram DIBuilder::createFunction(DIDescriptor Context,
                                        StringRef Name,
                                        StringRef LinkageName,
                                        DIFile File, unsigned LineNo,
-                                       DIType Ty,
+                                       DICompositeType Ty,
                                        bool isLocalToUnit, bool isDefinition,
                                        unsigned ScopeLine,
                                        unsigned Flags, bool isOptimized,
                                        Function *Fn,
                                        MDNode *TParams,
                                        MDNode *Decl) {
+  assert(Ty.getTag() == dwarf::DW_TAG_subroutine_type &&
+         "function types should be subroutines");
   Value *TElts[] = { GetTagConstant(VMContext, DW_TAG_base_type) };
   Value *Elts[] = {
     GetTagConstant(VMContext, dwarf::DW_TAG_subprogram),
@@ -1014,7 +1016,7 @@ DISubprogram DIBuilder::createMethod(DIDescriptor Context,
                                      StringRef Name,
                                      StringRef LinkageName,
                                      DIFile F,
-                                     unsigned LineNo, DIType Ty,
+                                     unsigned LineNo, DICompositeType Ty,
                                      bool isLocalToUnit,
                                      bool isDefinition,
                                      unsigned VK, unsigned VIndex,
@@ -1023,6 +1025,8 @@ DISubprogram DIBuilder::createMethod(DIDescriptor Context,
                                      bool isOptimized,
                                      Function *Fn,
                                      MDNode *TParam) {
+  assert(Ty.getTag() == dwarf::DW_TAG_subroutine_type &&
+         "function types should be subroutines");
   Value *TElts[] = { GetTagConstant(VMContext, DW_TAG_base_type) };
   Value *Elts[] = {
     GetTagConstant(VMContext, dwarf::DW_TAG_subprogram),

test/DebugInfo/X86/low-pc-cu.ll

@@ -18,12 +18,13 @@ entry:
 !1 = metadata !{i32 0}
 !3 = metadata !{metadata !5, metadata !12}
 !5 = metadata !{i32 786478, metadata !"_Z1qv", i32 0, metadata !6, metadata !"q", metadata !"q", metadata !6, i32 5, metadata !7, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, i32 ()* @_Z1qv, null, null, metadata !10} ; [ DW_TAG_subprogram ]
-!6 = metadata !{i32 786473, metadata !"foo.cpp", metadata !"/Users/echristo/tmp", null} ; [ DW_TAG_file_type ]
+!6 = metadata !{i32 786473, metadata !15} ; [ DW_TAG_file_type ]
 !7 = metadata !{i32 786453, i32 0, metadata !"", i32 0, i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !8, i32 0, i32 0} ; [ DW_TAG_subroutine_type ]
 !8 = metadata !{metadata !9}
 !9 = metadata !{i32 786468, null, metadata !"int", null, i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ]
 !10 = metadata !{metadata !11}
 !11 = metadata !{i32 786468}                      ; [ DW_TAG_base_type ]
-!12 = metadata !{i32 786478, metadata !"", i32 0, metadata !6, metadata !"t", metadata !"t", metadata !6, i32 2, metadata !7, i1 true, i1 true, i32 0, i32 0, null, i32 256, i1 false, null, null, null, metadata !10} ; [ DW_TAG_subprogram ]
+!12 = metadata !{i32 786478, metadata !15, metadata !6, metadata !"t", metadata !"t", metadata !"", i32 2, metadata !7, i1 true, i1 true, i32 0, i32 0, null, i32 256, i1 false, null, null, null, metadata !10} ; [ DW_TAG_subprogram ]
 !13 = metadata !{i32 7, i32 1, metadata !14, null}
 !14 = metadata !{i32 786443, metadata !5, i32 5, i32 1, metadata !6, i32 0} ; [ DW_TAG_lexical_block ]
+!15 = metadata !{metadata !"foo.cpp", metadata !"/Users/echristo/tmp"}