gdb/testsuite/dwarf: add support to generate DWARF 5 split compile units

Add support to the DWARF assembler to generate DWARF 5 split compile
units.  The assembler knows how to generate DWARF < 5 split compile
units (fission), DWARF 5 compile units, but not DWARF 5 split compile
units.  What's missing is:

 - using the right unit type in the header: skeleton for the unit in the
   main file and split_compile for the unit in the DWO file
 - have a way for the caller to specify the DWO ID that will end up in
   the unit header

Add a dwo_id parameter to the cu proc.  In addition to specifying the
DWO ID, the presence of this parameter tells the assembler to use the
skeleton or split_compile unit type.

This is used in a subsequent patch.

Change-Id: I05d9b189a0843ea6c2771b1d5e5a91762426dea9
Approved-By: Tom Tromey <tom@tromey.com>

diff --git a/gdb/testsuite/lib/dwarf.exp b/gdb/testsuite/lib/dwarf.exp
index 943b80cd9c787235a337cb22dee9437a9a7311c7..0a657f6f31923e38c54b499896b333f6d5c3c09d 100644 (file)
--- a/gdb/testsuite/lib/dwarf.exp
+++ b/gdb/testsuite/lib/dwarf.exp
@@ -1441,6 +1441,17 @@ namespace eval Dwarf {
     #                default = default
     # fission 0|1  - boolean indicating if generating Fission debug info
     #                default = 0
+    # dwo_id       - The value to use as the dwo_id field of skeleton and
+    #                split_compile unit headers.  May only be used with DWARF
+    #                version 5.
+    #
+    #                If a dwo_id value is specified (is non-zero), this unit is
+    #                assumed to be part of a skeleton/split_unit pair.  The unit
+    #                type will be chosen according to the `fission` value.
+    #
+    #                When using DWARF version 5 and fission is non-zero, it is
+    #                mandatory to provide a non-zero dwo_id value.
+    #                default = 0
     # label <label>
     #              - string indicating label to be defined at the start
     #                of the CU header.
@@ -1463,6 +1474,7 @@ namespace eval Dwarf {
        set _cu_version 4
        set _cu_addr_size default
        set _cu_is_fission 0
+       set dwo_id 0
        set section ".debug_info"
        set _abbrev_section ".debug_abbrev"
        set label ""
@@ -1474,6 +1486,7 @@ namespace eval Dwarf {
                version { set _cu_version $value }
                addr_size { set _cu_addr_size $value }
                fission { set _cu_is_fission $value }
+               dwo_id { set dwo_id $value }
                label { set label $value }
                default { error "unknown option $name" }
            }
@@ -1524,12 +1537,42 @@ namespace eval Dwarf {
 
        # The CU header for DWARF 4 and 5 are slightly different.
        if { $_cu_version == 5 } {
-           _op .byte 0x1 "DW_UT_compile"
+           # The presence of a DWO_ID indicates that we generate a skeleton
+           # or split_compile unit.
+           if { $dwo_id != 0 } {
+               if { $_cu_is_fission } {
+                   set unit_type_name "DW_UT_split_compile"
+               } else {
+                   set unit_type_name "DW_UT_skeleton"
+               }
+           } else {
+               set unit_type_name "DW_UT_compile"
+           }
+
+           _op .byte $_constants($unit_type_name) $unit_type_name
            _op .byte $_cu_addr_size "Pointer size"
            _op_offset $_cu_offset_size $my_abbrevs Abbrevs
+
+           # Output DWO ID, if specified.
+           if { $dwo_id != 0 } {
+               _op .8byte $dwo_id "DWO_ID"
+           } else {
+               # To help catch user errors: if the caller asked to put this
+               # unit in the DWO file but didn't provide a DWO ID, it is likely
+               # an error.
+               if { $_cu_is_fission } {
+                   error "DWO ID not specified for DWARF 5 split compile"
+               }
+           }
        } else {
            _op_offset $_cu_offset_size $my_abbrevs Abbrevs
            _op .byte $_cu_addr_size "Pointer size"
+
+           # For DWARF versions < 5, the DWO ID is not in the unit header,
+           # so it makes not sense to specify one.
+           if { $dwo_id != 0 } {
+               error "DWO ID specified for DWARF < 5 unit"
+           }
        }
 
        _defer_output $_abbrev_section {