[lldb/DWARF] Add support for DW_AT_loclists_base&DW_FORM_loclistx

Summary:
This adds support for DWARF5 location lists which are specified
indirectly, via an index into the debug_loclists offset table. This
includes parsing the DW_AT_loclists_base attribute which determines the
location of this offset table, and support for new form DW_FORM_loclistx
which is used in conjuction with DW_AT_location to refer to the location
lists in this way.

The code uses the llvm class to parse the offset information, and I've
also tried to structure it similarly to how the relevant llvm
functionality works.

Reviewers: JDevlieghere, aprantl, clayborg

Subscribers: lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D71268

1 files changed, 132 insertions, 0 deletions

diff --git a/lldb/test/Shell/SymbolFile/DWARF/DW_AT_loclists_base.s b/lldb/test/Shell/SymbolFile/DWARF/DW_AT_loclists_base.s
new file mode 100644
index 00000000000..831db3077ab
--- /dev/null
+++ b/lldb/test/Shell/SymbolFile/DWARF/DW_AT_loclists_base.s
@@ -0,0 +1,132 @@
+# REQUIRES: x86
+
+# RUN: llvm-mc -triple=x86_64-pc-linux -filetype=obj %s > %t
+# RUN: %lldb %t -o "image lookup -v -s lookup_loclists" -o exit | FileCheck %s
+
+# CHECK-LABEL: image lookup -v -s lookup_loclists
+# CHECK: Variable: {{.*}}, name = "x0", type = "int", location = DW_OP_reg0 RAX,
+# CHECK: Variable: {{.*}}, name = "x1", type = "int", location = ,
+
+loclists:
+        nop
+.Ltmp0:
+        nop
+lookup_loclists:
+.Ltmp1:
+        nop
+.Ltmp2:
+        nop
+.Ltmp3:
+        nop
+.Ltmp4:
+        nop
+.Lloclists_end:
+
+        .section        .debug_loclists,"",@progbits
+        .long   .Ldebug_loclist_table_end0-.Ldebug_loclist_table_start0 # Length
+.Ldebug_loclist_table_start0:
+        .short  5                       # Version
+        .byte   8                       # Address size
+        .byte   0                       # Segment selector size
+        .long   1                       # Offset entry count
+.Lloclists_table_base:
+        .long   .Ldebug_loc0-.Lloclists_table_base
+        .long   .Ldebug_loc1-.Lloclists_table_base
+.Ldebug_loc0:
+        .byte   4                       # DW_LLE_offset_pair
+        .uleb128 loclists-loclists
+        .uleb128  .Ltmp2-loclists
+        .uleb128 1                      # Expression size
+        .byte   80                      # super-register DW_OP_reg0
+        .byte   0                       # DW_LLE_end_of_list
+.Ldebug_loc1:
+        .byte   4                       # DW_LLE_offset_pair
+        .uleb128 .Ltmp3-loclists
+        .uleb128  .Ltmp4-loclists
+        .uleb128 1                      # Expression size
+        .byte   81                      # super-register DW_OP_reg1
+        .byte   0                       # DW_LLE_end_of_list
+.Ldebug_loclist_table_end0:
+
+        .section        .debug_abbrev,"",@progbits
+        .byte   1                       # Abbreviation Code
+        .byte   17                      # DW_TAG_compile_unit
+        .byte   1                       # DW_CHILDREN_yes
+        .byte   37                      # DW_AT_producer
+        .byte   8                       # DW_FORM_string
+        .byte   19                      # DW_AT_language
+        .byte   5                       # DW_FORM_data2
+        .uleb128 0x8c                   # DW_AT_loclists_base
+        .byte   0x17                    # DW_FORM_sec_offset
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   2                       # Abbreviation Code
+        .byte   46                      # DW_TAG_subprogram
+        .byte   1                       # DW_CHILDREN_yes
+        .byte   17                      # DW_AT_low_pc
+        .byte   1                       # DW_FORM_addr
+        .byte   18                      # DW_AT_high_pc
+        .byte   6                       # DW_FORM_data4
+        .byte   3                       # DW_AT_name
+        .byte   8                       # DW_FORM_string
+        .byte   73                      # DW_AT_type
+        .byte   19                      # DW_FORM_ref4
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   3                       # Abbreviation Code
+        .byte   5                       # DW_TAG_formal_parameter
+        .byte   0                       # DW_CHILDREN_no
+        .byte   2                       # DW_AT_location
+        .byte   0x22                    # DW_FORM_loclistx
+        .byte   3                       # DW_AT_name
+        .byte   8                       # DW_FORM_string
+        .byte   73                      # DW_AT_type
+        .byte   19                      # DW_FORM_ref4
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   4                       # Abbreviation Code
+        .byte   36                      # DW_TAG_base_type
+        .byte   0                       # DW_CHILDREN_no
+        .byte   3                       # DW_AT_name
+        .byte   8                       # DW_FORM_string
+        .byte   62                      # DW_AT_encoding
+        .byte   11                      # DW_FORM_data1
+        .byte   11                      # DW_AT_byte_size
+        .byte   11                      # DW_FORM_data1
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   0                       # EOM(3)
+
+        .section        .debug_info,"",@progbits
+.Lcu_begin0:
+        .long   .Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
+.Ldebug_info_start0:
+        .short  5                       # DWARF version number
+        .byte   1                       # DWARF Unit Type
+        .byte   8                       # Address Size (in bytes)
+        .long   .debug_abbrev           # Offset Into Abbrev. Section
+        .byte   1                       # Abbrev [1] 0xb:0x50 DW_TAG_compile_unit
+        .asciz  "Hand-written DWARF"    # DW_AT_producer
+        .short  12                      # DW_AT_language
+        .long   .Lloclists_table_base   # DW_AT_loclists_base
+        .byte   2                       # Abbrev [2] 0x2a:0x29 DW_TAG_subprogram
+        .quad   loclists                # DW_AT_low_pc
+        .long   .Lloclists_end-loclists # DW_AT_high_pc
+        .asciz  "loclists"              # DW_AT_name
+        .long   .Lint                   # DW_AT_type
+        .byte   3                       # Abbrev [3] DW_TAG_formal_parameter
+        .uleb128 0                      # DW_AT_location
+        .asciz  "x0"                    # DW_AT_name
+        .long   .Lint-.Lcu_begin0       # DW_AT_type
+        .byte   3                       # Abbrev [3] DW_TAG_formal_parameter
+        .uleb128 1                      # DW_AT_location
+        .asciz  "x1"                    # DW_AT_name
+        .long   .Lint-.Lcu_begin0       # DW_AT_type
+        .byte   0                       # End Of Children Mark
+.Lint:
+        .byte   4                       # Abbrev [4] 0x53:0x7 DW_TAG_base_type
+        .asciz  "int"                   # DW_AT_name
+        .byte   5                       # DW_AT_encoding
+        .byte   4                       # DW_AT_byte_size
+        .byte   0                       # End Of Children Mark
+.Ldebug_info_end0: