[lldb/DWARF] Fix DW_AT_addr_base & DW_AT_low_pc interaction

In DWARF5 DW_AT_low_pc (and DW_AT_entry_pc, and possibly others) can use
DW_FORM_addrx to refer to the address indirectly. This means we need to
have processed the DW_AT_addr_base attribute before we can do anything
with these.

Since we were processing the unit attributes serially, this created a
problem in cases where the DW_AT_addr_base comes after DW_AT_low_pc --
we would end up computing the wrong unit base address, which also
corrupted any values which later depended on that (for instance range
lists). Clang currently always emits DW_AT_addr_base last.

The fix is simple -- process DW_AT_addr_base first, regardless of its
position in the attribute list.

1 files changed, 106 insertions, 0 deletions

diff --git a/lldb/test/Shell/SymbolFile/DWARF/DW_AT_low_pc-addrx.s b/lldb/test/Shell/SymbolFile/DWARF/DW_AT_low_pc-addrx.s
new file mode 100644
index 00000000000..df089668cd9
--- /dev/null
+++ b/lldb/test/Shell/SymbolFile/DWARF/DW_AT_low_pc-addrx.s
@@ -0,0 +1,106 @@
+# REQUIRES: x86
+
+# RUN: llvm-mc -triple=x86_64-pc-linux -filetype=obj %s > %t
+# RUN: %lldb %t -o "image lookup -v -s lookup_rnglists" \
+# RUN:   -o exit | FileCheck %s
+
+# CHECK-LABEL: image lookup -v -s lookup_rnglists
+# CHECK:  Function: id = {0x7fffffff0000002d}, name = "rnglists", range = [0x0000000000000000-0x0000000000000003)
+# CHECK:    Blocks: id = {0x7fffffff0000002d}, range = [0x00000000-0x00000003)
+# CHECK-NEXT:       id = {0x7fffffff00000043}, range = [0x00000001-0x00000002)
+
+        .text
+rnglists:
+        nop
+.Lblock1_begin:
+lookup_rnglists:
+        nop
+.Lblock1_end:
+        nop
+.Lrnglists_end:
+
+        .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   17                      # DW_AT_low_pc
+        .byte   27                      # DW_FORM_addrx
+        .byte   18                      # DW_AT_high_pc
+        .byte   6                       # DW_FORM_data4
+        .byte   116                     # DW_AT_rnglists_base
+        .byte   23                      # DW_FORM_sec_offset
+        .byte   115                     # DW_AT_addr_base
+        .byte   23                      # 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   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   5                       # Abbreviation Code
+        .byte   11                      # DW_TAG_lexical_block
+        .byte   0                       # DW_CHILDREN_no
+        .byte   85                      # DW_AT_ranges
+        .byte   35                      # DW_FORM_rnglistx
+        .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] 0xc:0x5f DW_TAG_compile_unit
+        .asciz  "Hand-written DWARF"    # DW_AT_producer
+        .byte   0                       # DW_AT_low_pc
+        .long   .Lrnglists_end-rnglists # DW_AT_high_pc
+        .long   .Lrnglists_table_base0  # DW_AT_rnglists_base
+        .long   .Laddr_table_base0      # DW_AT_addr_base
+        .byte   2                       # Abbrev [2] 0x2b:0x37 DW_TAG_subprogram
+        .quad   rnglists                # DW_AT_low_pc
+        .long   .Lrnglists_end-rnglists # DW_AT_high_pc
+        .asciz  "rnglists"              # DW_AT_name
+        .byte   5                       # Abbrev [5] 0x52:0xf DW_TAG_lexical_block
+        .byte   0                       # DW_AT_ranges
+        .byte   0                       # End Of Children Mark
+        .byte   0                       # End Of Children Mark
+.Ldebug_info_end0:
+
+        .section        .debug_addr,"",@progbits
+        .long   .Ldebug_addr_end0-.Ldebug_addr_start0 # Length of contribution
+.Ldebug_addr_start0:
+        .short  5                       # DWARF version number
+        .byte   8                       # Address size
+        .byte   0                       # Segment selector size
+.Laddr_table_base0:
+        .quad   rnglists
+.Ldebug_addr_end0:
+
+        .section        .debug_rnglists,"",@progbits
+        .long   .Ldebug_rnglist_table_end0-.Ldebug_rnglist_table_start0 # Length
+.Ldebug_rnglist_table_start0:
+        .short  5                       # Version
+        .byte   8                       # Address size
+        .byte   0                       # Segment selector size
+        .long   1                       # Offset entry count
+.Lrnglists_table_base0:
+        .long   .Ldebug_ranges0-.Lrnglists_table_base0
+.Ldebug_ranges0:
+        .byte   4                       # DW_RLE_offset_pair
+        .uleb128 .Lblock1_begin-rnglists  #   starting offset
+        .uleb128 .Lblock1_end-rnglists    #   ending offset
+        .byte   0                       # DW_RLE_end_of_list
+.Ldebug_rnglist_table_end0: