This patch gets a DWARF parsing speed improvement by having DWARFAbbreviationDeclaration instances know if they have a fixed byte size. If an abbreviation has a fixed byte size that can be calculated given a DWARFUnit, then parsing a DIE becomes two steps: parse ULEB128 abbrev code, and then add constant size to the offset.
This patch also adds a fixed byte size to each DWARFAbbreviationDeclaration::AttributeSpec so that attributes can quickly skip their values if needed without the need to lookup the fixed for size.
Notable improvements:
- DWARFAbbreviationDeclaration::findAttributeIndex() now returns an Optional<uint32_t> instead of a uint32_t and we no longer have to look for the magic -1U return value
- Optional<uint32_t> DWARFAbbreviationDeclaration::findAttributeIndex(dwarf::Attribute attr) const;
- DWARFAbbreviationDeclaration now has a getAttributeValue() function that extracts an attribute value given a DIE offset that takes advantage of the DWARFAbbreviationDeclaration::AttributeSpec::ByteSize
- bool DWARFAbbreviationDeclaration::getAttributeValue(const uint32_t DIEOffset, const dwarf::Attribute Attr, const DWARFUnit &U, DWARFFormValue &FormValue) const;
- A DWARFAbbreviationDeclaration instance can return a fixed byte size for itself so DWARF parsing is faster:
- Optional<size_t> DWARFAbbreviationDeclaration::getFixedAttributesByteSize(const DWARFUnit &U) const;
- Any functions that used to take a "const DWARFUnit *U" that would crash if U was NULL now take a "const DWARFUnit &U" and are only called with a valid DWARFUnit
Differential Revision: https://reviews.llvm.org/D26567
llvm-svn: 286924
In preparation for a follow on patch that improves DWARF parsing speed, clean up DWARFFormValue so that we have can get the fixed byte size of a form value given a DWARFUnit or given the version, address byte size and dwarf32/64.
This patch cleans up code so that everyone is using one of the new DWARFFormValue functions:
static Optional<uint8_t> DWARFFormValue::getFixedByteSize(dwarf::Form Form, const DWARFUnit *U = nullptr);
static Optional<uint8_t> DWARFFormValue::getFixedByteSize(dwarf::Form Form, uint16_t Version, uint8_t AddrSize, bool Dwarf32);
This patch changes DWARFFormValue::skipValue() to rely on the output of DWARFFormValue::getFixedByteSize(...) instead of duplicating the code in each function. This will reduce the number of changes we need to make to DWARF to fewer places in DWARFFormValue when we add support for new form.
This patch also starts to support DWARF64 so that we can get correct byte sizes for forms that vary according the DWARF 32/64.
To reduce the code duplication a new FormSizeHelper pure virtual class was created that can be created as a FormSizeHelperDWARFUnit when you have a DWARFUnit, or FormSizeHelperManual where you manually specify the DWARF version, address byte size and DWARF32/DWARF64. There is now a single implementation of a function that gets the fixed byte size (instead of two where one took a DWARFUnit and one took the DWARF version, address byte size and DWARFFormat enum) and one function to skip the form values.
https://reviews.llvm.org/D26526
llvm-svn: 286597
Modifying DWARFFormValue to remember the DWARFUnit that it was encoded with can simplify the usage of instances of this class. Previously users would have to try and pass in the same DWARFUnit that was used to decode the form value and there was a possibility that a different DWARFUnit might be supplied to the functions that extract values (strings, CU relative references, addresses) and cause problems. This fixes this potential issue by storing the DWARFUnit inside the DWARFFormValue so that this mistake can't be made. Instances of DWARFFormValue are not stored permanently and are used as temporary values, so the increase in size of an instance of DWARFFormValue isn't a big deal. This makes decoding form values more bullet proof and is a change that will be used by future modifications.
https://reviews.llvm.org/D26052
llvm-svn: 285594
This change implements basic support for DWARF alternate sections
proposal: http://www.dwarfstd.org/ShowIssue.php?issue=120604.1&type=open
LLVM tools now understand new forms: DW_FORM_GNU_ref_alt and
DW_FORM_GNU_strp_alt, which are used as references to .debug_info and
.debug_str sections respectively, stored in a separate file, and
possibly shared between different executables / shared objects.
llvm-dwarfdump and llvm-symbolizer don't yet know how to access this
alternate debug file (usually pointed by .gnu_debugaltlink section),
but they can at lease properly parse and dump regular files, which
refer to it.
This change should fix crashes of llvm-dwarfdump and llvm-symbolizer on
files produced by running "dwz" tool. Such files are already installed
on some modern Linux distributions.
llvm-svn: 237721
In preparation for adding PDB support to LLVM, this moves the
DWARF parsing code to its own subdirectory under DebugInfo, and
renames LLVMDebugInfo to LLVMDebugInfoDWARF.
This is purely a mechanical / build system change.
Differential Revision: http://reviews.llvm.org/D7269
Reviewed by: Eric Christopher
llvm-svn: 227586
Greg Clayton