AsmPrinter: Allow null subroutine type

Currently the DWARF backend requires that subprograms have a type, and
the type is ignored if it has an empty type array.  The long term
direction here -- see PR23079 -- is instead to skip the type entirely if
there's no valid type.

It turns out we have cases in tree of missing types on subprograms, but
since they're not referenced by compile units, the backend never crashes
on them.  One option would be to add a Verifier check that subprograms
have types, and fix the bitrot.  However, this is a fair bit of churn
(20-30 testcases) that would be reversed anyway by PR23079.

I found this inconsistency because of a WIP patch and upgrade script for
PR23367 that started crashing on test/DebugInfo/2010-10-01-crash.ll.
This commit updates the testcase to reference the subprogram from the
compile unit, and fixes the resulting crash (in line with the direction
of PR23079).  This also updates `DIBuilder` to stop assuming a non-null
pointer for the subroutine types.

llvm-svn: 246333

4 files changed, 5 insertions, 9 deletions

diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
index 98d5c2e2f7c..eeacbdbf343 100644
--- a/llvm/include/llvm/IR/DebugInfoMetadata.h
+++ b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -99,6 +99,7 @@ class DITypeRefArray {
   const MDTuple *N = nullptr;
 
 public:
+  DITypeRefArray() = default;
   DITypeRefArray(const MDTuple *N) : N(N) {}
 
   explicit operator bool() const { return get(); }
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index d5ed0cd0945..d3e0b8b798c 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1195,11 +1195,10 @@ void DwarfUnit::applySubprogramAttributes(const DISubprogram *SP, DIE &SPDie,
        Language == dwarf::DW_LANG_ObjC))
     addFlag(SPDie, dwarf::DW_AT_prototyped);
 
-  const DISubroutineType *SPTy = SP->getType();
-  assert(SPTy->getTag() == dwarf::DW_TAG_subroutine_type &&
-         "the type of a subprogram should be a subroutine");
+  DITypeRefArray Args;
+  if (const DISubroutineType *SPTy = SP->getType())
+    Args = SPTy->getTypeArray();
 
-  auto Args = SPTy->getTypeArray();
   // Add a return type. If this is a type like a C/C++ void type we don't add a
   // return type.
   if (Args.size())
diff --git a/llvm/lib/IR/DIBuilder.cpp b/llvm/lib/IR/DIBuilder.cpp
index d1257ce78df..aedddb98330 100644
--- a/llvm/lib/IR/DIBuilder.cpp
+++ b/llvm/lib/IR/DIBuilder.cpp
@@ -689,8 +689,6 @@ DISubprogram *DIBuilder::createFunction(DIScope *Context, StringRef Name,
                                         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");
   auto *Node = getSubprogram(/* IsDistinct = */ isDefinition, VMContext,
                              DIScopeRef::get(getNonCompileUnitScope(Context)),
                              Name, LinkageName, File, LineNo, Ty, isLocalToUnit,
@@ -725,8 +723,6 @@ DIBuilder::createMethod(DIScope *Context, StringRef Name, StringRef LinkageName,
                         bool isLocalToUnit, bool isDefinition, unsigned VK,
                         unsigned VIndex, DIType *VTableHolder, unsigned Flags,
                         bool isOptimized, Function *Fn, MDNode *TParam) {
-  assert(Ty->getTag() == dwarf::DW_TAG_subroutine_type &&
-         "function types should be subroutines");
   assert(getNonCompileUnitScope(Context) &&
          "Methods should have both a Context and a context that isn't "
          "the compile unit.");
diff --git a/llvm/test/DebugInfo/2010-10-01-crash.ll b/llvm/test/DebugInfo/2010-10-01-crash.ll
index 914e300c346..6ae48f1c408 100644
--- a/llvm/test/DebugInfo/2010-10-01-crash.ll
+++ b/llvm/test/DebugInfo/2010-10-01-crash.ll
@@ -15,7 +15,7 @@ declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, i32, i32,
 !llvm.module.flags = !{!27}
 !0 = distinct !DISubprogram(name: "CGRectStandardize", linkageName: "CGRectStandardize", line: 54, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: false, file: !1, scope: null, function: void (i32*, i32*)* @CGRectStandardize)
 !1 = !DIFile(filename: "GSFusedSilica.m", directory: "/Volumes/Data/Users/sabre/Desktop")
-!2 = distinct !DICompileUnit(language: DW_LANG_ObjC, producer: "clang version 2.9 (trunk 115292)", isOptimized: true, runtimeVersion: 1, emissionKind: 0, file: !25, enums: !26, retainedTypes: !26)
+!2 = distinct !DICompileUnit(language: DW_LANG_ObjC, producer: "clang version 2.9 (trunk 115292)", isOptimized: true, runtimeVersion: 1, emissionKind: 0, file: !25, enums: !26, retainedTypes: !26, subprograms: !{!0})
 !5 = !DIDerivedType(tag: DW_TAG_typedef, name: "CGRect", line: 49, file: !25, baseType: null)
 !23 = !DILocalVariable(name: "rect", line: 53, arg: 2, scope: !0, file: !1, type: !5)
 !24 = !DILocation(line: 53, column: 33, scope: !0)