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
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 1d6480c..c835976 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -317,6 +317,8 @@
void writeDILexicalBlockFile(const DILexicalBlockFile *N,
SmallVectorImpl<uint64_t> &Record,
unsigned Abbrev);
+ void writeDICommonBlock(const DICommonBlock *N,
+ SmallVectorImpl<uint64_t> &Record, unsigned Abbrev);
void writeDINamespace(const DINamespace *N, SmallVectorImpl<uint64_t> &Record,
unsigned Abbrev);
void writeDIMacro(const DIMacro *N, SmallVectorImpl<uint64_t> &Record,
@@ -1686,6 +1688,20 @@
Record.clear();
}
+void ModuleBitcodeWriter::writeDICommonBlock(const DICommonBlock *N,
+ SmallVectorImpl<uint64_t> &Record,
+ unsigned Abbrev) {
+ Record.push_back(N->isDistinct());
+ Record.push_back(VE.getMetadataOrNullID(N->getScope()));
+ Record.push_back(VE.getMetadataOrNullID(N->getDecl()));
+ Record.push_back(VE.getMetadataOrNullID(N->getRawName()));
+ Record.push_back(VE.getMetadataOrNullID(N->getFile()));
+ Record.push_back(N->getLineNo());
+
+ Stream.EmitRecord(bitc::METADATA_COMMON_BLOCK, Record, Abbrev);
+ Record.clear();
+}
+
void ModuleBitcodeWriter::writeDINamespace(const DINamespace *N,
SmallVectorImpl<uint64_t> &Record,
unsigned Abbrev) {