Add LLVM IR debug info support for Fortran COMMON blocks

    COMMON blocks are a feature of Fortran that has no direct analog in C languages, but they are similar to data sections in assembly language programming. A COMMON block is a named area of memory that holds a collection of variables. Fortran subprograms may map the COMMON block memory area to their own, possibly distinct, non-empty list of variables. A Fortran COMMON block might look like the following example.

    COMMON /ALPHA/ I, J

    For this construct, the compiler generates a new scope-like DI construct (!DICommonBlock) into which variables (see I, J above) can be placed. As the common block implies a range of storage with global lifetime, the !DICommonBlock refers to a !DIGlobalVariable. The Fortran variable that comprise the COMMON block are also linked via metadata to offsets within the global variable that stands for the entire common block.

    @alpha_ = common global %alphabytes_ zeroinitializer, align 64, !dbg !27, !dbg !30, !dbg !33
    !14 = distinct !DISubprogram(…)
    !20 = distinct !DICommonBlock(scope: !14, declaration: !25, name: "alpha")
    !25 = distinct !DIGlobalVariable(scope: !20, name: "common alpha", type: !24)
    !27 = !DIGlobalVariableExpression(var: !25, expr: !DIExpression())
    !29 = distinct !DIGlobalVariable(scope: !20, name: "i", file: !3, type: !28)
    !30 = !DIGlobalVariableExpression(var: !29, expr: !DIExpression())
    !31 = distinct !DIGlobalVariable(scope: !20, name: "j", file: !3, type: !28)
    !32 = !DIExpression(DW_OP_plus_uconst, 4)
    !33 = !DIGlobalVariableExpression(var: !31, expr: !32)

    The DWARF generated for this is as follows.

    DW_TAG_common_block:
    DW_AT_name: alpha
    DW_AT_location: @alpha_+0
    DW_TAG_variable:
    DW_AT_name: common alpha
    DW_AT_type: array of 8 bytes
    DW_AT_location: @alpha_+0
    DW_TAG_variable:
    DW_AT_name: i
    DW_AT_type: integer*4
    DW_AT_location: @Alpha+0
    DW_TAG_variable:
    DW_AT_name: j
    DW_AT_type: integer*4
    DW_AT_location: @Alpha+4

Patch by Eric Schweitz!

Differential Revision: https://reviews.llvm.org/D54327

llvm-svn: 357934

5 files changed, 69 insertions, 1 deletions

diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index ad6c2c8e883..376262b8462 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -2001,6 +2001,19 @@ static void writeDINamespace(raw_ostream &Out, const DINamespace *N,
   Out << ")";
 }
 
+static void writeDICommonBlock(raw_ostream &Out, const DICommonBlock *N,
+                               TypePrinting *TypePrinter, SlotTracker *Machine,
+                               const Module *Context) {
+  Out << "!DICommonBlock(";
+  MDFieldPrinter Printer(Out, TypePrinter, Machine, Context);
+  Printer.printMetadata("scope", N->getRawScope(), false);
+  Printer.printMetadata("declaration", N->getRawDecl(), false);
+  Printer.printString("name", N->getName());
+  Printer.printMetadata("file", N->getRawFile());
+  Printer.printInt("line", N->getLineNo());
+  Out << ")";
+}
+
 static void writeDIMacro(raw_ostream &Out, const DIMacro *N,
                          TypePrinting *TypePrinter, SlotTracker *Machine,
                          const Module *Context) {
diff --git a/llvm/lib/IR/DIBuilder.cpp b/llvm/lib/IR/DIBuilder.cpp
index c248740b241..0cd33704093 100644
--- a/llvm/lib/IR/DIBuilder.cpp
+++ b/llvm/lib/IR/DIBuilder.cpp
@@ -805,6 +805,13 @@ DISubprogram *DIBuilder::createMethod(
   return SP;
 }
 
+DICommonBlock *DIBuilder::createCommonBlock(
+    DIScope *Scope, DIGlobalVariable *Decl, StringRef Name, DIFile *File,
+    unsigned LineNo) {
+  return DICommonBlock::get(
+      VMContext, Scope, Decl, Name, File, LineNo);
+}
+
 DINamespace *DIBuilder::createNameSpace(DIScope *Scope, StringRef Name,
                                         bool ExportSymbols) {
 
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index 0ae408af041..7158e5764fa 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -222,6 +222,9 @@ DIScopeRef DIScope::getScope() const {
   if (auto *NS = dyn_cast<DINamespace>(this))
     return NS->getScope();
 
+  if (auto *CB = dyn_cast<DICommonBlock>(this))
+    return CB->getScope();
+
   if (auto *M = dyn_cast<DIModule>(this))
     return M->getScope();
 
@@ -237,6 +240,8 @@ StringRef DIScope::getName() const {
     return SP->getName();
   if (auto *NS = dyn_cast<DINamespace>(this))
     return NS->getName();
+  if (auto *CB = dyn_cast<DICommonBlock>(this))
+    return CB->getName();
   if (auto *M = dyn_cast<DIModule>(this))
     return M->getName();
   assert((isa<DILexicalBlockBase>(this) || isa<DIFile>(this) ||
@@ -694,6 +699,17 @@ DINamespace *DINamespace::getImpl(LLVMContext &Context, Metadata *Scope,
   DEFINE_GETIMPL_STORE(DINamespace, (ExportSymbols), Ops);
 }
 
+DICommonBlock *DICommonBlock::getImpl(LLVMContext &Context, Metadata *Scope,
+                                      Metadata *Decl, MDString *Name,
+                                      Metadata *File, unsigned LineNo,
+                                      StorageType Storage, bool ShouldCreate) {
+  assert(isCanonical(Name) && "Expected canonical MDString");
+  DEFINE_GETIMPL_LOOKUP(DICommonBlock, (Scope, Decl, Name, File, LineNo));
+  // The nullptr is for DIScope's File operand. This should be refactored.
+  Metadata *Ops[] = {Scope, Decl, Name, File};
+  DEFINE_GETIMPL_STORE(DICommonBlock, (LineNo), Ops);
+}
+
 DIModule *DIModule::getImpl(LLVMContext &Context, Metadata *Scope,
                             MDString *Name, MDString *ConfigurationMacros,
                             MDString *IncludePath, MDString *ISysRoot,
diff --git a/llvm/lib/IR/LLVMContextImpl.h b/llvm/lib/IR/LLVMContextImpl.h
index 42dd471af9e..aaa765be9fa 100644
--- a/llvm/lib/IR/LLVMContextImpl.h
+++ b/llvm/lib/IR/LLVMContextImpl.h
@@ -789,6 +789,31 @@ template <> struct MDNodeKeyImpl<DINamespace> {
   }
 };
 
+template <> struct MDNodeKeyImpl<DICommonBlock> {
+  Metadata *Scope;
+  Metadata *Decl;
+  MDString *Name;
+  Metadata *File;
+  unsigned LineNo;
+
+  MDNodeKeyImpl(Metadata *Scope, Metadata *Decl, MDString *Name,
+                Metadata *File, unsigned LineNo)
+      : Scope(Scope), Decl(Decl), Name(Name), File(File), LineNo(LineNo) {}
+  MDNodeKeyImpl(const DICommonBlock *N)
+      : Scope(N->getRawScope()), Decl(N->getRawDecl()), Name(N->getRawName()),
+        File(N->getRawFile()), LineNo(N->getLineNo()) {}
+
+  bool isKeyOf(const DICommonBlock *RHS) const {
+    return Scope == RHS->getRawScope() && Decl == RHS->getRawDecl() &&
+      Name == RHS->getRawName() && File == RHS->getRawFile() &&
+      LineNo == RHS->getLineNo();
+  }
+
+  unsigned getHashValue() const {
+    return hash_combine(Scope, Decl, Name, File, LineNo);
+  }
+};
+
 template <> struct MDNodeKeyImpl<DIModule> {
   Metadata *Scope;
   MDString *Name;
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index c3710870442..837f2d0e9c8 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -1156,6 +1156,14 @@ void Verifier::visitDILexicalBlockFile(const DILexicalBlockFile &N) {
   visitDILexicalBlockBase(N);
 }
 
+void Verifier::visitDICommonBlock(const DICommonBlock &N) {
+  AssertDI(N.getTag() == dwarf::DW_TAG_common_block, "invalid tag", &N);
+  if (auto *S = N.getRawScope())
+    AssertDI(isa<DIScope>(S), "invalid scope ref", &N, S);
+  if (auto *S = N.getRawDecl())
+    AssertDI(isa<DIGlobalVariable>(S), "invalid declaration", &N, S);
+}
+
 void Verifier::visitDINamespace(const DINamespace &N) {
   AssertDI(N.getTag() == dwarf::DW_TAG_namespace, "invalid tag", &N);
   if (auto *S = N.getRawScope())
@@ -1224,7 +1232,6 @@ void Verifier::visitDIGlobalVariable(const DIGlobalVariable &N) {
   visitDIVariable(N);
 
   AssertDI(N.getTag() == dwarf::DW_TAG_variable, "invalid tag", &N);
-  AssertDI(!N.getName().empty(), "missing global variable name", &N);
   AssertDI(isType(N.getRawType()), "invalid type ref", &N, N.getRawType());
   AssertDI(N.getType(), "missing global variable type", &N);
   if (auto *Member = N.getRawStaticDataMemberDeclaration()) {