[CodeView] Don't emit debuginfo for imported symbols

Emitting symbol information requires us to have a definition for the
symbol.  A symbol reference is insufficient.

This fixes PR28123.

llvm-svn: 272738

2 files changed, 32 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index a90ce05249e..3b7815f3e0b 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -249,7 +249,8 @@ void CodeViewDebug::endModule() {
 
   // Emit per-function debug information.
   for (auto &P : FnDebugInfo)
-    emitDebugInfoForFunction(P.first, P.second);
+    if (!P.first->isDeclarationForLinker())
+      emitDebugInfoForFunction(P.first, P.second);
 
   // Emit global variable debug information.
   emitDebugInfoForGlobals();
@@ -1318,7 +1319,7 @@ void CodeViewDebug::emitDebugInfoForGlobals() {
     MCSymbol *EndLabel = nullptr;
     for (const DIGlobalVariable *G : CU->getGlobalVariables()) {
       if (const auto *GV = dyn_cast_or_null<GlobalVariable>(G->getVariable())) {
-        if (!GV->hasComdat()) {
+        if (!GV->hasComdat() && !GV->isDeclarationForLinker()) {
           if (!EndLabel) {
             OS.AddComment("Symbol subsection for globals");
             EndLabel = beginCVSubsection(ModuleSubstreamKind::Symbols);
diff --git a/llvm/test/DebugInfo/COFF/global-dllimport.ll b/llvm/test/DebugInfo/COFF/global-dllimport.ll
new file mode 100644
index 00000000000..9d21a43e5eb
--- /dev/null
+++ b/llvm/test/DebugInfo/COFF/global-dllimport.ll
@@ -0,0 +1,29 @@
+; RUN: llc < %s | FileCheck %s
+
+; CHECK-NOT: S_GDATA32
+
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i686-pc-windows-msvc"
+
+@"\01?id@?$numpunct@D@@0HA" = available_externally dllimport global i32 0, align 4
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!13, !14}
+!llvm.ident = !{!15}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.9.0 (trunk 272628) (llvm/trunk 272566)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3)
+!1 = !DIFile(filename: "/usr/local/google/home/majnemer/Downloads/<stdin>", directory: "/usr/local/google/home/majnemer/llvm/src")
+!2 = !{}
+!3 = !{!4}
+!4 = distinct !DIGlobalVariable(name: "id", linkageName: "\01?id@?$numpunct@D@@0HA", scope: !0, file: !5, line: 4, type: !6, isLocal: false, isDefinition: true, variable: i32* @"\01?id@?$numpunct@D@@0HA", declaration: !7)
+!5 = !DIFile(filename: "/usr/local/google/home/majnemer/Downloads/t.ii", directory: "/usr/local/google/home/majnemer/llvm/src")
+!6 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!7 = !DIDerivedType(tag: DW_TAG_member, name: "id", scope: !8, file: !5, line: 2, baseType: !6, flags: DIFlagStaticMember)
+!8 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "numpunct<char>", file: !5, line: 2, size: 8, align: 8, elements: !9, templateParams: !10)
+!9 = !{!7}
+!10 = !{!11}
+!11 = !DITemplateTypeParameter(type: !12)
+!12 = !DIBasicType(name: "char", size: 8, align: 8, encoding: DW_ATE_signed_char)
+!13 = !{i32 2, !"CodeView", i32 1}
+!14 = !{i32 2, !"Debug Info Version", i32 3}
+!15 = !{!"clang version 3.9.0 (trunk 272628) (llvm/trunk 272566)"}