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