[DWARFYAML] Teach yaml2obj emit the correct line table program.

[Higuoxing]

Summary

The following issues are addressed in this patch.

1. The operands of DW_LNE_set_discriminator should be an ULEB128 number rather than an address.
2. Test the emitted opcodes.

[Higuoxing]

Update.

[jhenderson]

LGTM, since it's an improvement on the current behaviour, but I think my inline comment should be addressed in a follow-up (assuming you agree, of course).

llvm/test/tools/yaml2obj/ELF/DWARF/debug-line.yaml

489–494

It's good to have a test for this, but I actually think the behaviour is incorrect for yaml2obj. It's possible to have line tables without .debug_info, and there's no reference from a line table to .debug_info anyway. The address should be inferred from the target machine, in my opinion (in this case it would be 8).

From the DWARF v4 spec:

2. DW_LNE_set_address The DW_LNE_set_address opcode takes a single relocatable address as an operand. The size of the operand is the size of an address on the target machine.

[Higuoxing]

llvm/test/tools/yaml2obj/ELF/DWARF/debug-line.yaml

489–494

Oh, I see. What do you think of having an optional field AddressSize for the line table. If it's specified, yaml2obj will emit addresses according to the value.

[jhenderson]

llvm/test/tools/yaml2obj/ELF/DWARF/debug-line.yaml

489–494

We should probably only have an explicit AddressSize field for v5 line tables, I think, but we could use the same internal logic that that uses to identify it's default value when missing (which should match that of other sections), to determine the address size.

[Higuoxing]

llvm/test/tools/yaml2obj/ELF/DWARF/debug-line.yaml

489–494

I got it. We should make the address size inferred from the target machine when the version is less than or equal to 4. When the version is 5, there should be an optional field AddressSize. In a follow-up patch, the reference of address size of debug_info should be removed and this test case should be modified, right?

[jhenderson]

llvm/test/tools/yaml2obj/ELF/DWARF/debug-line.yaml

489–494

Yes, exactly.

[Higuoxing]

llvm/test/tools/yaml2obj/ELF/DWARF/debug-line.yaml

489–494

Thanks! I think it's not very difficult to fix it. I can give a fix and rebase this patch on that.

[Higuoxing]

Remove test case (j)

[jhenderson]

LGTM!

llvm/lib/ObjectYAML/DWARFEmitter.cpp

for (const auto &LineTable : DI.DebugLines) {
 
     for (auto Op : LineTable.Opcodes) {
       writeInteger((uint8_t)Op.Opcode, OS, DI.IsLittleEndian);
       if (Op.Opcode == 0) {
         encodeULEB128(Op.ExtLen, OS);
         writeInteger((uint8_t)Op.SubOpcode, OS, DI.IsLittleEndian);
         switch (Op.SubOpcode) {
         case dwarf::DW_LNE_set_address:
-        case dwarf::DW_LNE_set_discriminator:
-          // FIXME: The operand of set_discriminator is not an address.
           cantFail(writeVariableSizedInteger(Op.Data, AddrSize, OS,
                                              DI.IsLittleEndian));
           break;
         case dwarf::DW_LNE_define_file:
           emitFileEntry(OS, Op.FileEntry);
           break;
+        case dwarf::DW_LNE_set_discriminator:
+          encodeULEB128(Op.Data, OS);
+          break;
         case dwarf::DW_LNE_end_sequence:
           break;
         default:
           for (auto OpByte : Op.UnknownOpcodeData)
             writeInteger((uint8_t)OpByte, OS, DI.IsLittleEndian);
         }
       } else if (Op.Opcode < LineTable.OpcodeBase) {
         switch (Op.Opcode) {

llvm/test/tools/yaml2obj/ELF/DWARF/debug-line.yaml

- Length:                0x1234
       StandardOpcodeLengths: []
       IncludeDirs:           []
       Files:                 []
       Opcodes:
         - Opcode:    DW_LNS_extended_op
           ExtLen:    9
           SubOpcode: DW_LNE_set_address
           Data:      [[ADDR]]
+
+## i) Test that yaml2obj is able to emit correct opcodes.
+
+# RUN: yaml2obj --docnum=9 %s -o %t9.o
+# RUN: llvm-readelf --hex-dump=.debug_line %t9.o | FileCheck %s --check-prefix=OPCODES
+
+#      OPCODES: Hex dump of section '.debug_line':
+# OPCODES-NEXT: 0x00000000 34120000 04003412 00000101 01010e0d 4.....4.........
+##                         ^-------                            unit_length (4-byte)
+##                                  ^---                       version (2-byte)
+##                                      ^--------              header_length (4-byte)
+##                                               ^-            minimum_instruction_length (1-byte)
+##                                                 ^-          maximum_operations_per_instruction (1-byte)
+##                                                    ^-       default_is_stmt (1-byte)
+##                                                      ^-     line_base (1-byte)
+##                                                        ^-   line_range (1-byte)
+##                                                          ^- opcode_base (1-byte)
+# OPCODES-NEXT: 0x00000010 00000102 b42403b4 2404b424 05b42406 .....$..$..$..$.
+##                         ^-                                  null byte for terminating include_directories
+##                           ^-                                null byte for terminating file_names
+##                             ^-                              DW_LNS_copy (1-byte)
+##                               ^-                            DW_LNS_advance_pc
+##                                  ^---                       operands[0] (ULEB128) 0x1234
+##                                      ^-                     DW_LNS_advance_line
+##                                        ^----                operands[0] (SLEB128) 0x1234
+##                                             ^-              DW_LNS_set_file
+##                                               ^---          operands[0] (ULEB128) 0x1234
+##                                                    ^-       DW_LNS_set_column
+##                                                      ^---   operands[0] (ULEB128) 0x1234
+##                                                          ^- DW_LNS_negate_stmt
+# OPCODES-NEXT: 0x00000020 07080934 120a0b0c b4240009 01000902 ...4.....$......
+##                         ^-                                  DW_LNS_set_basic_block
+##                           ^-                                DW_LNS_const_add_pc
+##                             ^-                              DW_LNS_fixed_advance_pc
+##                               ^----                         operands[0] (uhalf, 2-byte)
+##                                    ^-                       DW_LNS_set_prologue_end
+##                                      ^-                     DW_LNS_set_epilogue_begin
+##                                        ^-                   DW_LNS_set_isa
+##                                           ^---              operands[0] (ULEB128) 0x1234
+##                                               ^-            DW_LNS_extended_op
+##                                                 ^-          extended op length (ULEB128) 0x09
+##                                                    ^-       DW_LNE_end_sequence
+##                                                      ^-     DW_LNS_extended_op
+##                                                        ^-   extended op length (ULEB128) 0x09
+##                                                          ^- DW_LNE_set_address
+# OPCODES-NEXT: 0x00000030 34120000 00000000 00090361 62636400 4..........abcd.
+##                         ^----------------                   operands[0] (8-byte)
+##                                           ^-                DW_LNS_extended_op
+##                                             ^-              extended op length (ULEB128) 0x09
+##                                               ^-            DW_LNE_define_file
+##                                                 ^---------- operands[0] "abcd\0"
+# OPCODES-NEXT: 0x00000040 b424b424 b4240009 04b424            .$.$.$....$
+##                         ^---                                operands[1] (ULEB128) 0x1234
+##                             ^---                            operands[2] (ULEB128) 0x1234
+##                                  ^---                       operands[3] (ULEB128) 0x1234
+##                                      ^-                     DW_LNS_extended_op
+##                                        ^-                   extended op length (ULEB128) 0x09
+##                                           ^-                DW_LNE_set_discriminator
+##                                             ^---            operands[0] (ULEB128) 0x1234
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64
+DWARF:
+  debug_line:
+    - Length:                0x1234
+      Version:               4
+      PrologueLength:        0x1234
+      MinInstLength:         1
+      MaxOpsPerInst:         1
+      DefaultIsStmt:         1
+      LineBase:              1
+      LineRange:             14
+      OpcodeBase:            13
+      StandardOpcodeLengths: []
+      IncludeDirs:           []
+      Files:                 []
+      Opcodes:
+        - Opcode:    DW_LNS_copy
+        - Opcode:    DW_LNS_advance_pc
+          Data:      0x1234
+        - Opcode:    DW_LNS_advance_line
+          SData:     0x1234
+        - Opcode:    DW_LNS_set_file
+          Data:      0x1234
+        - Opcode:    DW_LNS_set_column
+          Data:      0x1234
+        - Opcode:    DW_LNS_negate_stmt
+        - Opcode:    DW_LNS_set_basic_block
+        - Opcode:    DW_LNS_const_add_pc
+        - Opcode:    DW_LNS_fixed_advance_pc
+          Data:      0x1234
+        - Opcode:    DW_LNS_set_prologue_end
+        - Opcode:    DW_LNS_set_epilogue_begin
+        - Opcode:    DW_LNS_set_isa
+          Data:      0x1234
+        - Opcode:    DW_LNS_extended_op
+          ExtLen:    0x09
+          SubOpcode: DW_LNE_end_sequence
+        - Opcode:    DW_LNS_extended_op
+          ExtLen:    0x09
+          SubOpcode: DW_LNE_set_address
+          Data:      0x1234
+        - Opcode:    DW_LNS_extended_op
+          ExtLen:    0x09
+          SubOpcode: DW_LNE_define_file
+          FileEntry:
+            Name:    abcd
+            DirIdx:  0x1234
+            ModTime: 0x1234
+            Length:  0x1234
+        - Opcode:    DW_LNS_extended_op
+          ExtLen:    0x09
+          SubOpcode: DW_LNE_set_discriminator
+          Data:      0x1234