[DWARF/AccelTable] Remove getDIESectionOffset for DWARF v5 entries

Summary:
This method was not correct for entries in DWO files as it assumed it
could just add up the CU and DIE offsets to get the absolute DIE offset.
This is not correct for the DWO files, as here the CU offset will
reference the skeleton unit, whereas the DIE offset will be the offset
in the full unit in the DWO file.

Unfortunately, this means that we are not able to determine the absolute
DIE offset using the information in the .debug_names section alone,
which means we have to offload some of this work to the users of this
class.

To demonstrate how this can be done, I've added/fixed the ability to
lookup entries using accelerator tables in DWO files in llvm-dwarfdump.
To make this happen, I've needed to make two extra changes in other
classes:
- made the DWARFContext method to lookup a CU based on the section
  offset public. I've needed this functionality to lookup a CU, and this
  seems like a useful thing in general.
- made DWARFUnit::getDWOId call extractDIEsIfNeeded. Before this, the
  DWOId was filled in only if the root DIE happened to be parsed
  before we called the accessor. Since the lazy parsing is supposed to
  happen under the hood, calling extractDIEsIfNeeded seems appropriate.

Reviewers: JDevlieghere, aprantl, dblaikie

Subscribers: mgrang, llvm-commits

Differential Revision: https://reviews.llvm.org/D48009

llvm-svn: 334578

1 files changed, 162 insertions, 0 deletions

diff --git a/llvm/test/tools/llvm-dwarfdump/X86/debug-names-find-dwo.s b/llvm/test/tools/llvm-dwarfdump/X86/debug-names-find-dwo.s
new file mode 100644
index 00000000000..a12aa2e90f1
--- /dev/null
+++ b/llvm/test/tools/llvm-dwarfdump/X86/debug-names-find-dwo.s
@@ -0,0 +1,162 @@
+# RUN: llvm-mc -triple x86_64-pc-linux %s -filetype=obj | \
+# RUN:   llvm-dwarfdump -find=foobar - | FileCheck %s
+
+# CHECK: DW_TAG_variable
+# CHECK-NEXT: DW_AT_name ("foobar")
+
+	.text
+	.file	"<stdin>"
+	.file	1 "/tmp/cu1.c"
+	.type	foobar,@object          # @foobar
+	.comm	foobar,8,8
+	.section	.debug_str,"MS",@progbits,1
+.Lskel_string0:
+	.asciz	"foo.dwo"               # string offset=0
+.Lskel_string1:
+	.asciz	"/tmp"                  # string offset=8
+.Lskel_string2:
+	.asciz	"foobar"                # string offset=13
+	.section	.debug_loc.dwo,"",@progbits
+	.section	.debug_abbrev,"",@progbits
+	.byte	1                       # Abbreviation Code
+	.byte	17                      # DW_TAG_compile_unit
+	.byte	0                       # DW_CHILDREN_no
+	.byte	16                      # DW_AT_stmt_list
+	.byte	23                      # DW_FORM_sec_offset
+	.ascii	"\260B"                 # DW_AT_GNU_dwo_name
+	.byte	14                      # DW_FORM_strp
+	.byte	27                      # DW_AT_comp_dir
+	.byte	14                      # DW_FORM_strp
+	.ascii	"\261B"                 # DW_AT_GNU_dwo_id
+	.byte	7                       # DW_FORM_data8
+	.ascii	"\263B"                 # DW_AT_GNU_addr_base
+	.byte	23                      # DW_FORM_sec_offset
+	.byte	0                       # EOM(1)
+	.byte	0                       # EOM(2)
+	.byte	0                       # EOM(3)
+	.section	.debug_info,"",@progbits
+.Lcu_begin0:
+	.long	32                      # Length of Unit
+	.short	4                       # DWARF version number
+	.long	.debug_abbrev           # Offset Into Abbrev. Section
+	.byte	8                       # Address Size (in bytes)
+	.byte	1                       # Abbrev [1] 0xb:0x19 DW_TAG_compile_unit
+	.long	0                       # DW_AT_stmt_list
+	.long	.Lskel_string0          # DW_AT_GNU_dwo_name
+	.long	.Lskel_string1          # DW_AT_comp_dir
+	.quad	-1328675031687321003    # DW_AT_GNU_dwo_id
+	.long	.debug_addr             # DW_AT_GNU_addr_base
+	.section	.debug_ranges,"",@progbits
+	.section	.debug_macinfo,"",@progbits
+	.byte	0                       # End Of Macro List Mark
+	.section	.debug_str.dwo,"MS",@progbits,1
+.Linfo_string0:
+	.asciz	"foo.dwo"               # string offset=0
+.Linfo_string1:
+	.asciz	"clang version 7.0.0 (trunk 325496) (llvm/trunk 325732)" # string offset=8
+.Linfo_string2:
+	.asciz	"/tmp/cu1.c"            # string offset=63
+.Linfo_string3:
+	.asciz	"foobar"                # string offset=74
+	.section	.debug_str_offsets.dwo,"",@progbits
+	.long	0
+	.long	8
+	.long	63
+	.long	74
+	.section	.debug_info.dwo,"",@progbits
+	.long	34                      # Length of Unit
+	.short	4                       # DWARF version number
+	.long	0                       # Offset Into Abbrev. Section
+	.byte	8                       # Address Size (in bytes)
+	.byte	1                       # Abbrev [1] 0xb:0x1b DW_TAG_compile_unit
+	.byte	0                       # DW_AT_GNU_dwo_name
+	.byte	1                       # DW_AT_producer
+	.short	12                      # DW_AT_language
+	.byte	2                       # DW_AT_name
+	.quad	-1328675031687321003    # DW_AT_GNU_dwo_id
+	.byte	2                       # Abbrev [2] 0x19:0xb DW_TAG_variable
+	.byte	3                       # DW_AT_name
+	.long	36                      # DW_AT_type
+                                        # DW_AT_external
+	.byte	1                       # DW_AT_decl_file
+	.byte	1                       # DW_AT_decl_line
+	.byte	2                       # DW_AT_location
+	.byte	251
+	.byte	0
+	.byte	3                       # Abbrev [3] 0x24:0x1 DW_TAG_pointer_type
+	.byte	0                       # End Of Children Mark
+	.section	.debug_abbrev.dwo,"",@progbits
+	.byte	1                       # Abbreviation Code
+	.byte	17                      # DW_TAG_compile_unit
+	.byte	1                       # DW_CHILDREN_yes
+	.ascii	"\260B"                 # DW_AT_GNU_dwo_name
+	.ascii	"\202>"                 # DW_FORM_GNU_str_index
+	.byte	37                      # DW_AT_producer
+	.ascii	"\202>"                 # DW_FORM_GNU_str_index
+	.byte	19                      # DW_AT_language
+	.byte	5                       # DW_FORM_data2
+	.byte	3                       # DW_AT_name
+	.ascii	"\202>"                 # DW_FORM_GNU_str_index
+	.ascii	"\261B"                 # DW_AT_GNU_dwo_id
+	.byte	7                       # DW_FORM_data8
+	.byte	0                       # EOM(1)
+	.byte	0                       # EOM(2)
+	.byte	2                       # Abbreviation Code
+	.byte	52                      # DW_TAG_variable
+	.byte	0                       # DW_CHILDREN_no
+	.byte	3                       # DW_AT_name
+	.ascii	"\202>"                 # DW_FORM_GNU_str_index
+	.byte	73                      # DW_AT_type
+	.byte	19                      # DW_FORM_ref4
+	.byte	63                      # DW_AT_external
+	.byte	25                      # DW_FORM_flag_present
+	.byte	58                      # DW_AT_decl_file
+	.byte	11                      # DW_FORM_data1
+	.byte	59                      # DW_AT_decl_line
+	.byte	11                      # DW_FORM_data1
+	.byte	2                       # DW_AT_location
+	.byte	24                      # DW_FORM_exprloc
+	.byte	0                       # EOM(1)
+	.byte	0                       # EOM(2)
+	.byte	3                       # Abbreviation Code
+	.byte	15                      # DW_TAG_pointer_type
+	.byte	0                       # DW_CHILDREN_no
+	.byte	0                       # EOM(1)
+	.byte	0                       # EOM(2)
+	.byte	0                       # EOM(3)
+	.section	.debug_addr,"",@progbits
+	.quad	foobar
+	.section	.debug_names,"",@progbits
+	.long	.Lnames_end0-.Lnames_start0 # Header: unit length
+.Lnames_start0:
+	.short	5                       # Header: version
+	.short	0                       # Header: padding
+	.long	1                       # Header: compilation unit count
+	.long	0                       # Header: local type unit count
+	.long	0                       # Header: foreign type unit count
+	.long	1                       # Header: bucket count
+	.long	1                       # Header: name count
+	.long	.Lnames_abbrev_end0-.Lnames_abbrev_start0 # Header: abbreviation table size
+	.long	8                       # Header: augmentation string size
+	.ascii	"LLVM0700"              # Header: augmentation string
+	.long	.Lcu_begin0             # Compilation unit 0
+	.long	1                       # Bucket 0
+	.long	-35364674               # Hash in Bucket 0
+	.long	.Lskel_string2          # String in Bucket 0: foobar
+	.long	.Lnames0-.Lnames_entries0 # Offset in Bucket 0
+.Lnames_abbrev_start0:
+	.byte	52                      # Abbrev code
+	.byte	52                      # DW_TAG_variable
+	.byte	3                       # DW_IDX_die_offset
+	.byte	19                      # DW_FORM_ref4
+	.byte	0                       # End of abbrev
+	.byte	0                       # End of abbrev
+	.byte	0                       # End of abbrev list
+.Lnames_abbrev_end0:
+.Lnames_entries0:
+.Lnames0:
+	.byte	52                      # Abbreviation code
+	.long	25                      # DW_IDX_die_offset
+	.long	0                       # End of list: foobar
+	.p2align	2
+.Lnames_end0: