[CodeView] Don't output S_UDT symbols for forward decls.

S_UDT symbols are the debugger's "index" for all the structs,
typedefs, classes, and enums in a program.  If any of those
structs/classes don't have a complete declaration, or if there
is a typedef to something that doesn't have a complete definition,
then emitting the S_UDT is unhelpful because it doesn't give
the debugger enough information to do anything useful.  On the
other hand, it results in a huge size blow-up in the resulting
PDB, which is exacerbated by an order of magnitude when linking
with /DEBUG:FASTLINK.

With this patch, we drop S_UDT records for types that refer either
directly or indirectly (e.g. through a typedef, pointer, etc) to
a class/struct/union/enum without a complete definition.  This
brings us about 50% of the way towards parity with /DEBUG:FASTLINK
PDBs generated from cl-compiled object files.

Differential Revision: https://reviews.llvm.org/D37162

llvm-svn: 311904

1 files changed, 120 insertions, 0 deletions

diff --git a/llvm/test/DebugInfo/COFF/purge-typedef-udts.ll b/llvm/test/DebugInfo/COFF/purge-typedef-udts.ll
new file mode 100644
index 00000000000..28106d74e90
--- /dev/null
+++ b/llvm/test/DebugInfo/COFF/purge-typedef-udts.ll
@@ -0,0 +1,120 @@
+; RUN: llc < %s -filetype=obj | llvm-readobj - -codeview | FileCheck %s
+source_filename = "test/DebugInfo/COFF/purge-typedef-udts.ll"
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i686-pc-windows-msvc19.11.25506"
+
+; C++ source to regenerate:
+; $ cat t.cpp
+; struct Foo;
+; struct Bar {
+;   Bar() {}
+;   int X;
+; };
+;
+; typedef Foo FooTypedef;
+; typedef Bar BarTypedef;
+;
+; int func(void *F) { return 7; }
+; int func(const FooTypedef *F) { return func((void*)F); }
+; int func(const BarTypedef *B) { return func((void*)B->X); }
+
+; CHECK-NOT: UDTName: FooTypedef
+; CHECK: UDTName: BarTypedef
+
+%struct.Foo = type opaque
+%struct.Bar = type { i32 }
+
+; Function Attrs: noinline nounwind optnone
+define i32 @"\01?func@@YAHPAX@Z"(i8* %F) #0 !dbg !10 {
+entry:
+  %F.addr = alloca i8*, align 4
+  store i8* %F, i8** %F.addr, align 4
+  call void @llvm.dbg.declare(metadata i8** %F.addr, metadata !14, metadata !DIExpression()), !dbg !15
+  ret i32 7, !dbg !16
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+; Function Attrs: noinline nounwind optnone
+define i32 @"\01?func@@YAHPBUFoo@@@Z"(%struct.Foo* %F) #0 !dbg !17 {
+entry:
+  %F.addr = alloca %struct.Foo*, align 4
+  store %struct.Foo* %F, %struct.Foo** %F.addr, align 4
+  call void @llvm.dbg.declare(metadata %struct.Foo** %F.addr, metadata !24, metadata !DIExpression()), !dbg !25
+  %0 = load %struct.Foo*, %struct.Foo** %F.addr, align 4, !dbg !26
+  %1 = bitcast %struct.Foo* %0 to i8*, !dbg !26
+  %call = call i32 @"\01?func@@YAHPAX@Z"(i8* %1), !dbg !27
+  ret i32 %call, !dbg !28
+}
+
+; Function Attrs: noinline nounwind optnone
+define i32 @"\01?func@@YAHPBUBar@@@Z"(%struct.Bar* %B) #0 !dbg !29 {
+entry:
+  %B.addr = alloca %struct.Bar*, align 4
+  store %struct.Bar* %B, %struct.Bar** %B.addr, align 4
+  call void @llvm.dbg.declare(metadata %struct.Bar** %B.addr, metadata !42, metadata !DIExpression()), !dbg !43
+  %0 = load %struct.Bar*, %struct.Bar** %B.addr, align 4, !dbg !44
+  %X = getelementptr inbounds %struct.Bar, %struct.Bar* %0, i32 0, i32 0, !dbg !45
+  %1 = load i32, i32* %X, align 4, !dbg !45
+  %2 = inttoptr i32 %1 to i8*, !dbg !46
+  %call = call i32 @"\01?func@@YAHPAX@Z"(i8* %2), !dbg !47
+  ret i32 %call, !dbg !48
+}
+
+attributes #0 = { noinline nounwind optnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="pentium4" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone speculatable }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!5, !6, !7, !8}
+!llvm.ident = !{!9}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 6.0.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3)
+!1 = !DIFile(filename: "t.cpp", directory: "D:\5Csrc\5Cllvmbuild\5Cninja", checksumkind: CSK_MD5, checksum: "27c44c8a5531845f61f582a24ef5c151")
+!2 = !{}
+!3 = !{!4}
+!4 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 32)
+!5 = !{i32 1, !"NumRegisterParameters", i32 0}
+!6 = !{i32 2, !"CodeView", i32 1}
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = !{i32 1, !"wchar_size", i32 2}
+!9 = !{!"clang version 6.0.0 "}
+!10 = distinct !DISubprogram(name: "func", linkageName: "\01?func@@YAHPAX@Z", scope: !1, file: !1, line: 10, type: !11, isLocal: false, isDefinition: true, scopeLine: 10, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!11 = !DISubroutineType(types: !12)
+!12 = !{!13, !4}
+!13 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!14 = !DILocalVariable(name: "F", arg: 1, scope: !10, file: !1, line: 10, type: !4)
+!15 = !DILocation(line: 10, column: 16, scope: !10)
+!16 = !DILocation(line: 10, column: 21, scope: !10)
+!17 = distinct !DISubprogram(name: "func", linkageName: "\01?func@@YAHPBUFoo@@@Z", scope: !1, file: !1, line: 11, type: !18, isLocal: false, isDefinition: true, scopeLine: 11, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!18 = !DISubroutineType(types: !19)
+!19 = !{!13, !20}
+!20 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !21, size: 32)
+!21 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !22)
+!22 = !DIDerivedType(tag: DW_TAG_typedef, name: "FooTypedef", file: !1, line: 7, baseType: !23)
+!23 = !DICompositeType(tag: DW_TAG_structure_type, name: "Foo", file: !1, line: 1, flags: DIFlagFwdDecl, identifier: ".?AUFoo@@")
+!24 = !DILocalVariable(name: "F", arg: 1, scope: !17, file: !1, line: 11, type: !20)
+!25 = !DILocation(line: 11, column: 28, scope: !17)
+!26 = !DILocation(line: 11, column: 52, scope: !17)
+!27 = !DILocation(line: 11, column: 40, scope: !17)
+!28 = !DILocation(line: 11, column: 33, scope: !17)
+!29 = distinct !DISubprogram(name: "func", linkageName: "\01?func@@YAHPBUBar@@@Z", scope: !1, file: !1, line: 12, type: !30, isLocal: false, isDefinition: true, scopeLine: 12, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!30 = !DISubroutineType(types: !31)
+!31 = !{!13, !32}
+!32 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !33, size: 32)
+!33 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !34)
+!34 = !DIDerivedType(tag: DW_TAG_typedef, name: "BarTypedef", file: !1, line: 8, baseType: !35)
+!35 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Bar", file: !1, line: 2, size: 32, elements: !36, identifier: ".?AUBar@@")
+!36 = !{!37, !38}
+!37 = !DIDerivedType(tag: DW_TAG_member, name: "X", scope: !35, file: !1, line: 4, baseType: !13, size: 32)
+!38 = !DISubprogram(name: "Bar", scope: !35, file: !1, line: 3, type: !39, isLocal: false, isDefinition: false, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: false)
+!39 = !DISubroutineType(cc: DW_CC_BORLAND_thiscall, types: !40)
+!40 = !{null, !41}
+!41 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !35, size: 32, flags: DIFlagArtificial | DIFlagObjectPointer)
+!42 = !DILocalVariable(name: "B", arg: 1, scope: !29, file: !1, line: 12, type: !32)
+!43 = !DILocation(line: 12, column: 28, scope: !29)
+!44 = !DILocation(line: 12, column: 52, scope: !29)
+!45 = !DILocation(line: 12, column: 55, scope: !29)
+!46 = !DILocation(line: 12, column: 45, scope: !29)
+!47 = !DILocation(line: 12, column: 40, scope: !29)
+!48 = !DILocation(line: 12, column: 33, scope: !29)