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

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 1ab2702941d..f14ef36afb0 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -4664,6 +4664,24 @@ bool LLParser::ParseDILexicalBlockFile(MDNode *&Result, bool IsDistinct) {
   return false;
 }
 
+/// ParseDICommonBlock:
+///   ::= !DICommonBlock(scope: !0, file: !2, name: "COMMON name", line: 9)
+bool LLParser::ParseDICommonBlock(MDNode *&Result, bool IsDistinct) {
+#define VISIT_MD_FIELDS(OPTIONAL, REQUIRED)                                    \
+  REQUIRED(scope, MDField, );                                                  \
+  OPTIONAL(declaration, MDField, );                                            \
+  OPTIONAL(name, MDStringField, );                                             \
+  OPTIONAL(file, MDField, );                                                   \
+  OPTIONAL(line, LineField, );						       
+  PARSE_MD_FIELDS();
+#undef VISIT_MD_FIELDS
+
+  Result = GET_OR_DISTINCT(DICommonBlock,
+                           (Context, scope.Val, declaration.Val, name.Val,
+                            file.Val, line.Val));
+  return false;
+}
+
 /// ParseDINamespace:
 ///   ::= !DINamespace(scope: !0, file: !2, name: "SomeNamespace", line: 9)
 bool LLParser::ParseDINamespace(MDNode *&Result, bool IsDistinct) {