[COFF, Dwarf] Don't emit DW_AT_location for dllimported entities

There exists no relocation which can describe the address of a
dllimported variable: do not try to describe their location.

llvm-svn: 274986

3 files changed, 93 insertions, 55 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 3f6616fb519..7822814c7a0 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -148,62 +148,69 @@ DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(
   // Add location.
   bool addToAccelTable = false;
   if (auto *Global = dyn_cast_or_null<GlobalVariable>(GV->getVariable())) {
-    addToAccelTable = true;
-    DIELoc *Loc = new (DIEValueAllocator) DIELoc;
-    const MCSymbol *Sym = Asm->getSymbol(Global);
-    if (Global->isThreadLocal()) {
-      if (Asm->TM.Options.EmulatedTLS) {
-        // TODO: add debug info for emulated thread local mode.
-      } else {
-        // FIXME: Make this work with -gsplit-dwarf.
-        unsigned PointerSize = Asm->getDataLayout().getPointerSize();
-        assert((PointerSize == 4 || PointerSize == 8) &&
-               "Add support for other sizes if necessary");
-        // Based on GCC's support for TLS:
-        if (!DD->useSplitDwarf()) {
-          // 1) Start with a constNu of the appropriate pointer size
-          addUInt(*Loc, dwarf::DW_FORM_data1, PointerSize == 4
-                                                  ? dwarf::DW_OP_const4u
-                                                  : dwarf::DW_OP_const8u);
-          // 2) containing the (relocated) offset of the TLS variable
-          //    within the module's TLS block.
-          addExpr(*Loc, dwarf::DW_FORM_udata,
-                  Asm->getObjFileLowering().getDebugThreadLocalSymbol(Sym));
+    // We cannot describe the location of dllimport'd variables: the computation
+    // of their address requires loads from the IAT.
+    if (!Global->hasDLLImportStorageClass()) {
+      addToAccelTable = true;
+      DIELoc *Loc = new (DIEValueAllocator) DIELoc;
+      const MCSymbol *Sym = Asm->getSymbol(Global);
+      if (Global->isThreadLocal()) {
+        if (Asm->TM.Options.EmulatedTLS) {
+          // TODO: add debug info for emulated thread local mode.
         } else {
-          addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_GNU_const_index);
-          addUInt(*Loc, dwarf::DW_FORM_udata,
-                  DD->getAddressPool().getIndex(Sym, /* TLS */ true));
+          // FIXME: Make this work with -gsplit-dwarf.
+          unsigned PointerSize = Asm->getDataLayout().getPointerSize();
+          assert((PointerSize == 4 || PointerSize == 8) &&
+                 "Add support for other sizes if necessary");
+          // Based on GCC's support for TLS:
+          if (!DD->useSplitDwarf()) {
+            // 1) Start with a constNu of the appropriate pointer size
+            addUInt(*Loc, dwarf::DW_FORM_data1, PointerSize == 4
+                                                    ? dwarf::DW_OP_const4u
+                                                    : dwarf::DW_OP_const8u);
+            // 2) containing the (relocated) offset of the TLS variable
+            //    within the module's TLS block.
+            addExpr(*Loc, dwarf::DW_FORM_udata,
+                    Asm->getObjFileLowering().getDebugThreadLocalSymbol(Sym));
+          } else {
+            addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_GNU_const_index);
+            addUInt(*Loc, dwarf::DW_FORM_udata,
+                    DD->getAddressPool().getIndex(Sym, /* TLS */ true));
+          }
+          // 3) followed by an OP to make the debugger do a TLS lookup.
+          addUInt(*Loc, dwarf::DW_FORM_data1,
+                  DD->useGNUTLSOpcode() ? dwarf::DW_OP_GNU_push_tls_address
+                                        : dwarf::DW_OP_form_tls_address);
         }
-        // 3) followed by an OP to make the debugger do a TLS lookup.
-        addUInt(*Loc, dwarf::DW_FORM_data1,
-                DD->useGNUTLSOpcode() ? dwarf::DW_OP_GNU_push_tls_address
-                                      : dwarf::DW_OP_form_tls_address);
+      } else {
+        DD->addArangeLabel(SymbolCU(this, Sym));
+        addOpAddress(*Loc, Sym);
       }
-    } else {
-      DD->addArangeLabel(SymbolCU(this, Sym));
-      addOpAddress(*Loc, Sym);
-    }
 
-    addBlock(*VariableDIE, dwarf::DW_AT_location, Loc);
-    if (DD->useAllLinkageNames())
-      addLinkageName(*VariableDIE, GV->getLinkageName());
+      addBlock(*VariableDIE, dwarf::DW_AT_location, Loc);
+      if (DD->useAllLinkageNames())
+        addLinkageName(*VariableDIE, GV->getLinkageName());
+    }
   } else if (const ConstantInt *CI =
                  dyn_cast_or_null<ConstantInt>(GV->getVariable())) {
     addConstantValue(*VariableDIE, CI, GTy);
   } else if (const ConstantExpr *CE = getMergedGlobalExpr(GV->getVariable())) {
-    addToAccelTable = true;
-    // GV is a merged global.
-    DIELoc *Loc = new (DIEValueAllocator) DIELoc;
     auto *Ptr = cast<GlobalValue>(CE->getOperand(0));
-    MCSymbol *Sym = Asm->getSymbol(Ptr);
-    DD->addArangeLabel(SymbolCU(this, Sym));
-    addOpAddress(*Loc, Sym);
-    addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_constu);
-    SmallVector<Value *, 3> Idx(CE->op_begin() + 1, CE->op_end());
-    addUInt(*Loc, dwarf::DW_FORM_udata,
-            Asm->getDataLayout().getIndexedOffsetInType(Ptr->getValueType(), Idx));
-    addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_plus);
-    addBlock(*VariableDIE, dwarf::DW_AT_location, Loc);
+    if (!Ptr->hasDLLImportStorageClass()) {
+      addToAccelTable = true;
+      // GV is a merged global.
+      DIELoc *Loc = new (DIEValueAllocator) DIELoc;
+      MCSymbol *Sym = Asm->getSymbol(Ptr);
+      DD->addArangeLabel(SymbolCU(this, Sym));
+      addOpAddress(*Loc, Sym);
+      addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_constu);
+      SmallVector<Value *, 3> Idx(CE->op_begin() + 1, CE->op_end());
+      addUInt(*Loc, dwarf::DW_FORM_udata,
+              Asm->getDataLayout().getIndexedOffsetInType(Ptr->getValueType(),
+                                                          Idx));
+      addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_plus);
+      addBlock(*VariableDIE, dwarf::DW_AT_location, Loc);
+    }
   }
 
   if (addToAccelTable) {
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 6a5e29a4ff0..e2e6954bd1c 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1053,14 +1053,18 @@ void DwarfUnit::constructTemplateValueParameterDIE(
     if (ConstantInt *CI = mdconst::dyn_extract<ConstantInt>(Val))
       addConstantValue(ParamDIE, CI, resolve(VP->getType()));
     else if (GlobalValue *GV = mdconst::dyn_extract<GlobalValue>(Val)) {
-      // For declaration non-type template parameters (such as global values and
-      // functions)
-      DIELoc *Loc = new (DIEValueAllocator) DIELoc;
-      addOpAddress(*Loc, Asm->getSymbol(GV));
-      // Emit DW_OP_stack_value to use the address as the immediate value of the
-      // parameter, rather than a pointer to it.
-      addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_stack_value);
-      addBlock(ParamDIE, dwarf::DW_AT_location, Loc);
+      // We cannot describe the location of dllimport'd entities: the
+      // computation of their address requires loads from the IAT.
+      if (!GV->hasDLLImportStorageClass()) {
+        // For declaration non-type template parameters (such as global values
+        // and functions)
+        DIELoc *Loc = new (DIEValueAllocator) DIELoc;
+        addOpAddress(*Loc, Asm->getSymbol(GV));
+        // Emit DW_OP_stack_value to use the address as the immediate value of
+        // the parameter, rather than a pointer to it.
+        addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_stack_value);
+        addBlock(ParamDIE, dwarf::DW_AT_location, Loc);
+      }
     } else if (VP->getTag() == dwarf::DW_TAG_GNU_template_template_param) {
       assert(isa<MDString>(Val));
       addString(ParamDIE, dwarf::DW_AT_GNU_template_name,
diff --git a/llvm/test/DebugInfo/X86/dllimport.ll b/llvm/test/DebugInfo/X86/dllimport.ll
new file mode 100644
index 00000000000..60c3116cf2e
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/dllimport.ll
@@ -0,0 +1,27 @@
+; RUN: llc -mtriple=i686-pc-windows-msvc -O0 -filetype=obj < %s | llvm-dwarfdump -debug-dump=info - | FileCheck %s
+
+; CHECK-NOT: DW_AT_location
+
+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@?$numpunct@D@@0HA" = available_externally dllimport global i32 0, align 4
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!13, !14}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.9.0 (trunk 272628) (llvm/trunk 272566)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3)
+!1 = !DIFile(filename: "/usr/local/google/home/majnemer/Downloads/<stdin>", directory: "/usr/local/google/home/majnemer/llvm/src")
+!2 = !{}
+!3 = !{!4}
+!4 = distinct !DIGlobalVariable(name: "id", linkageName: "\01?id@?$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, !"Dwarf Version", i32 3}
+!14 = !{i32 2, !"Debug Info Version", i32 3}