[IR] Make TypeFinder aware of DIArgList values

[dstenb]

Summary

TypeFinder did not find types under DIArgList. This resulted in a case
of invalid IR after GlobalOpt removed a global that was the only
non-DIArgList use of a struct type.

error: use of undefined type named 'struct.S'
  call void @llvm.dbg.value(metadata !DIArgList([1 x %struct.S]* undef, i64 %idxprom),
                                             metadata !24, metadata !DIExpression([...])), !dbg !26

[jmorse]

LGTM

llvm/test/Transforms/GlobalOpt/deadglobal-diarglist-use.ll

32–33

(We usually delete any un-necessary attributes for DI)

[dstenb]

llvm/test/Transforms/GlobalOpt/deadglobal-diarglist-use.ll

32–33

Thanks, I'll fix this when landing this.

llvm/lib/IR/TypeFinder.cpp

 //===- TypeFinder.cpp - Implement the TypeFinder class --------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the TypeFinder class for the IR library.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/IR/TypeFinder.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Constant.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IR/Use.h"
 #include "llvm/IR/User.h"

 
 /// incorporateMDNode - This method is used to walk the operands of an MDNode to
 /// find types hiding within.
 void TypeFinder::incorporateMDNode(const MDNode *V) {
   // Already visited?
   if (!VisitedMetadata.insert(V).second)
     return;
 
+  // The arguments in DIArgList are not exposed as operands, so handle such
+  // nodes specifically here.
+  if (const auto *AL = dyn_cast<DIArgList>(V)) {
+    for (auto *Arg : AL->getArgs())
+      incorporateValue(Arg->getValue());
+    return;
+  }
+
   // Look in operands for types.
   for (Metadata *Op : V->operands()) {
     if (!Op)
       continue;
     if (auto *N = dyn_cast<MDNode>(Op)) {
       incorporateMDNode(N);
       continue;
     }
     if (auto *C = dyn_cast<ConstantAsMetadata>(Op)) {
       incorporateValue(C->getValue());
       continue;
     }
   }
 }

llvm/test/Transforms/GlobalOpt/deadglobal-diarglist-use.ll

+; RUN: opt < %s -globalopt -S | llvm-as | llvm-dis | FileCheck %s
+
+; The %struct.S type would not get emitted after @s was removed, resulting in
+; llvm-as failing to parse the dbg.value intrinsic using that type. The
+; FileCheck checks are just added to verify that the desired transformation is
+; done.
+
+; CHECK-NOT: @s
+; CHECK: %struct.S = type { i32 }
+; CHECK-NOT: @s
+
+; CHECK: call void @llvm.dbg.value(metadata !DIArgList([1 x %struct.S]* undef
+
+%struct.S = type { i32 }
+
+@s = internal global [1 x %struct.S] zeroinitializer, align 4, !dbg !0
+@idx = dso_local global i32 0, align 4, !dbg !6
+
+define dso_local void @fn() !dbg !20 {
+entry:
+  %0 = load i32, i32* @idx, align 4, !dbg !26
+  %idxprom = sext i32 %0 to i64, !dbg !26
+  call void @llvm.dbg.value(metadata !DIArgList([1 x %struct.S]* @s, i64 %idxprom), metadata !24, metadata !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_constu, 4, DW_OP_mul, DW_OP_plus, DW_OP_stack_value)), !dbg !26
+  ret void, !dbg !26
+}
+
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!15, !16, !17, !18}
+!llvm.ident = !{!19}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "s", scope: !2, file: !3, line: 1, type: !9, isLocal: true, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 13.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, splitDebugInlining: false, nameTableKind: None)
+!3 = !DIFile(filename: "foo.c", directory: "/")
+!4 = !{}
+!5 = !{!0, !6}
+!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
+!7 = distinct !DIGlobalVariable(name: "idx", scope: !2, file: !3, line: 2, type: !8, isLocal: false, isDefinition: true)
+!8 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!9 = !DICompositeType(tag: DW_TAG_array_type, baseType: !10, size: 32, elements: !13)
+!10 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "S", file: !3, line: 1, size: 32, elements: !11)
+!11 = !{!12}
+!12 = !DIDerivedType(tag: DW_TAG_member, name: "data", scope: !10, file: !3, line: 1, baseType: !8, size: 32)
+!13 = !{!14}
+!14 = !DISubrange(count: 1)
+!15 = !{i32 7, !"Dwarf Version", i32 4}
+!16 = !{i32 2, !"Debug Info Version", i32 3}
+!17 = !{i32 1, !"wchar_size", i32 4}
+!18 = !{i32 7, !"uwtable", i32 1}
+!19 = !{!"clang version 13.0.0"}
+!20 = distinct !DISubprogram(name: "fn", scope: !3, file: !3, line: 4, type: !21, scopeLine: 4, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !23)
+!21 = !DISubroutineType(types: !22)
+!22 = !{null}
+!23 = !{!24}
+!24 = !DILocalVariable(name: "local", scope: !20, file: !3, line: 5, type: !25)
+!25 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 64)
+!26 = !DILocation(line: 5, scope: !20)