[RemoveDIs][NFC] Fix rotten green C API test (#92362)

`llvm_test_dibuilder(/*NewDebugInfoMode=*/true)` isn't currently executed in 
`return llvm_test_dibuilder(false) && llvm_test_dibuilder(true);`
because `llvm_test_dibuilder` returns 0 for success.

Split the llvm-c-test flag `--test-dibuilder` into two, one for the old and
one for the new debug info format. Add another lit test for the new format.

Now that the test actually runs, it crashes using the new format with
`llvm/lib/IR/LLVMContextImpl.cpp:53:llvm::LLVMContextImpl::~LLVMContextImpl(): Assertion 'TrailingDbgRecords.empty() && "DbgRecords in blocks not cleaned"' failed. Aborted`.

Insert terminators into the blocks so that we don't leave the debug records
trailing, unattached to any instructions, which fixes that.

Author: OCHyams

llvm/test/Bindings/llvm-c/debug_info.ll

@@ -1,4 +1,4 @@
-; RUN: llvm-c-test --test-dibuilder | FileCheck %s
+; RUN: llvm-c-test --test-dibuilder-old-debuginfo-format | FileCheck %s
 
 ; CHECK: ; ModuleID = 'debuginfo.c'
 ; CHECK-NEXT: source_filename = "debuginfo.c"
@@ -8,8 +8,10 @@
 ; CHECK-NEXT:   call void @llvm.dbg.declare(metadata i64 0, metadata !38, metadata !DIExpression()), !dbg !43
 ; CHECK-NEXT:   call void @llvm.dbg.declare(metadata i64 0, metadata !39, metadata !DIExpression()), !dbg !43
 ; CHECK-NEXT:   call void @llvm.dbg.declare(metadata i64 0, metadata !40, metadata !DIExpression()), !dbg !43
-; CHECK:      vars:                                             ; No predecessors!
+; CHECK-NEXT:   br label %vars
+; CHECK:      vars:
 ; CHECK-NEXT:   call void @llvm.dbg.value(metadata i64 0, metadata !41, metadata !DIExpression(DW_OP_constu, 0, DW_OP_stack_value)), !dbg !44
+; CHECK-NEXT:   ret i64 0
 ; CHECK-NEXT: }
 
 ; CHECK:      ; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)

llvm/test/Bindings/llvm-c/debug_info_new_format.ll

@@ -0,0 +1,66 @@
+; RUN: llvm-c-test --test-dibuilder-new-debuginfo-format | FileCheck %s
+;; Duplicate of debug_info.ll using debug records instead of intrinsics.
+
+; CHECK: ; ModuleID = 'debuginfo.c'
+; CHECK-NEXT: source_filename = "debuginfo.c"
+
+; CHECK:      define i64 @foo(i64 %0, i64 %1, <10 x i64> %2) !dbg !31 {
+; CHECK-NEXT: entry:
+; CHECK-NEXT:     #dbg_declare(i64 0, !38, !DIExpression(), !43)
+; CHECK-NEXT:     #dbg_declare(i64 0, !39, !DIExpression(), !43)
+; CHECK-NEXT:     #dbg_declare(i64 0, !40, !DIExpression(), !43)
+; CHECK-NEXT:   br label %vars
+; CHECK:      vars:
+; CHECK-NEXT:     #dbg_value(i64 0, !41, !DIExpression(DW_OP_constu, 0, DW_OP_stack_value), !44)
+; CHECK-NEXT:   ret i64 0
+; CHECK-NEXT: }
+
+; CHECK:      !llvm.dbg.cu = !{!0}
+; CHECK-NEXT: !FooType = !{!28}
+; CHECK-NEXT: !EnumTest = !{!3}
+
+; CHECK:      !0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "llvm-c-test", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !11, imports: !19, macros: !23, splitDebugInlining: false, sysroot: "/")
+; CHECK-NEXT: !1 = !DIFile(filename: "debuginfo.c", directory: ".")
+; CHECK-NEXT: !2 = !{!3}
+; CHECK-NEXT: !3 = !DICompositeType(tag: DW_TAG_enumeration_type, name: "EnumTest", scope: !4, file: !1, baseType: !6, size: 64, elements: !7)
+; CHECK-NEXT: !4 = !DINamespace(name: "NameSpace", scope: !5)
+; CHECK-NEXT: !5 = !DIModule(scope: null, name: "llvm-c-test", includePath: "/test/include/llvm-c-test.h")
+; CHECK-NEXT: !6 = !DIBasicType(name: "Int64", size: 64)
+; CHECK-NEXT: !7 = !{!8, !9, !10}
+; CHECK-NEXT: !8 = !DIEnumerator(name: "Test_A", value: 0, isUnsigned: true)
+; CHECK-NEXT: !9 = !DIEnumerator(name: "Test_B", value: 1, isUnsigned: true)
+; CHECK-NEXT: !10 = !DIEnumerator(name: "Test_B", value: 2, isUnsigned: true)
+; CHECK-NEXT: !11 = !{!12, !16}
+; CHECK-NEXT: !12 = !DIGlobalVariableExpression(var: !13, expr: !DIExpression(DW_OP_constu, 0, DW_OP_stack_value))
+; CHECK-NEXT: !13 = distinct !DIGlobalVariable(name: "globalClass", scope: !5, file: !1, line: 1, type: !14, isLocal: true, isDefinition: true)
+; CHECK-NEXT: !14 = !DICompositeType(tag: DW_TAG_structure_type, name: "TestClass", scope: !1, file: !1, line: 42, size: 64, flags: DIFlagObjcClassComplete, elements: !15)
+; CHECK-NEXT: !15 = !{}
+; CHECK-NEXT: !16 = !DIGlobalVariableExpression(var: !17, expr: !DIExpression(DW_OP_constu, 0, DW_OP_stack_value))
+; CHECK-NEXT: !17 = distinct !DIGlobalVariable(name: "global", scope: !5, file: !1, line: 1, type: !18, isLocal: true, isDefinition: true)
+; CHECK-NEXT: !18 = !DIDerivedType(tag: DW_TAG_typedef, name: "int64_t", scope: !1, file: !1, line: 42, baseType: !6)
+; CHECK-NEXT: !19 = !{!20, !22}
+; CHECK-NEXT: !20 = !DIImportedEntity(tag: DW_TAG_imported_module, scope: !5, entity: !21, file: !1, line: 42)
+; CHECK-NEXT: !21 = !DIModule(scope: null, name: "llvm-c-test-import", includePath: "/test/include/llvm-c-test-import.h")
+; CHECK-NEXT: !22 = !DIImportedEntity(tag: DW_TAG_imported_module, scope: !5, entity: !20, file: !1, line: 42)
+; CHECK-NEXT: !23 = !{!24}
+; CHECK-NEXT: !24 = !DIMacroFile(file: !1, nodes: !25)
+; CHECK-NEXT: !25 = !{!26, !27}
+; CHECK-NEXT: !26 = !DIMacro(type: DW_MACINFO_define, name: "SIMPLE_DEFINE")
+; CHECK-NEXT: !27 = !DIMacro(type: DW_MACINFO_define, name: "VALUE_DEFINE", value: "1")
+; CHECK-NEXT: !28 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !29, size: 192, dwarfAddressSpace: 0)
+; CHECK-NEXT: !29 = !DICompositeType(tag: DW_TAG_structure_type, name: "MyStruct", scope: !4, file: !1, size: 192, elements: !30, runtimeLang: DW_LANG_C89, identifier: "MyStruct")
+; CHECK-NEXT: !30 = !{!6, !6, !6}
+; CHECK-NEXT: !31 = distinct !DISubprogram(name: "foo", linkageName: "foo", scope: !1, file: !1, line: 42, type: !32, scopeLine: 42, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition, unit: !0, retainedNodes: !37)
+; CHECK-NEXT: !32 = !DISubroutineType(types: !33)
+; CHECK-NEXT: !33 = !{!6, !6, !34}
+; CHECK-NEXT: !34 = !DICompositeType(tag: DW_TAG_array_type, baseType: !6, size: 640, flags: DIFlagVector, elements: !35)
+; CHECK-NEXT: !35 = !{!36}
+; CHECK-NEXT: !36 = !DISubrange(count: 10, lowerBound: 0)
+; CHECK-NEXT: !37 = !{!38, !39, !40, !41}
+; CHECK-NEXT: !38 = !DILocalVariable(name: "a", arg: 1, scope: !31, file: !1, line: 42, type: !6)
+; CHECK-NEXT: !39 = !DILocalVariable(name: "b", arg: 2, scope: !31, file: !1, line: 42, type: !6)
+; CHECK-NEXT: !40 = !DILocalVariable(name: "c", arg: 3, scope: !31, file: !1, line: 42, type: !34)
+; CHECK-NEXT: !41 = !DILocalVariable(name: "d", scope: !42, file: !1, line: 43, type: !6)
+; CHECK-NEXT: !42 = distinct !DILexicalBlock(scope: !31, file: !1, line: 42)
+; CHECK-NEXT: !43 = !DILocation(line: 42, scope: !31)
+; CHECK-NEXT: !44 = !DILocation(line: 43, scope: !31)

llvm/tools/llvm-c-test/debuginfo.c

@@ -215,10 +215,26 @@ int llvm_test_dibuilder(bool NewDebugInfoFormat) {
 
   LLVMDIBuilderFinalize(DIB);
 
+  // Using the new debug format, debug records get attached to instructions.
+  // Insert a `br` and `ret` now to absorb the debug records which are
+  // currently "trailing", meaning that they're associated with a block
+  // but no particular instruction, which is only valid as a transient state.
+  LLVMContextRef Ctx = LLVMGetModuleContext(M);
+  LLVMBuilderRef Builder = LLVMCreateBuilderInContext(Ctx);
+  LLVMPositionBuilderAtEnd(Builder, FooEntryBlock);
+  // Build `br label %vars` in entry.
+  LLVMBuildBr(Builder, FooVarBlock);
+  // Build `ret i64 0` in vars.
+  LLVMPositionBuilderAtEnd(Builder, FooVarBlock);
+  LLVMTypeRef I64 = LLVMInt64TypeInContext(Ctx);
+  LLVMValueRef Zero = LLVMConstInt(I64, 0, false);
+  LLVMBuildRet(Builder, Zero);
+
   char *MStr = LLVMPrintModuleToString(M);
   puts(MStr);
   LLVMDisposeMessage(MStr);
 
+  LLVMDisposeBuilder(Builder);
   LLVMDisposeDIBuilder(DIB);
   LLVMDisposeModule(M);
 

llvm/tools/llvm-c-test/main.c

@@ -109,8 +109,12 @@ int main(int argc, char **argv) {
     return llvm_echo();
   } else if (argc == 2 && !strcmp(argv[1], "--test-diagnostic-handler")) {
     return llvm_test_diagnostic_handler();
-  } else if (argc == 2 && !strcmp(argv[1], "--test-dibuilder")) {
-    return llvm_test_dibuilder(false) && llvm_test_dibuilder(true);
+  } else if (argc == 2 &&
+             !strcmp(argv[1], "--test-dibuilder-old-debuginfo-format")) {
+    return llvm_test_dibuilder(false);
+  } else if (argc == 2 &&
+             !strcmp(argv[1], "--test-dibuilder-new-debuginfo-format")) {
+    return llvm_test_dibuilder(true);
   } else {
     print_usage();
   }