Summary:
The code in DWARFCompileUnit::BuildAddressRangeTable tries hard to avoid
relying on DW_AT_low/high_pc for compile unit range information, and
this logic is a big cause of llvm/lldb divergence in the lowest layers
of dwarf parsing code.
The implicit assumption in that code is that this information (as opposed to
DW_AT_ranges) is unreliable. However, I have not been able to verify
that assumption. It is definitely not true for all present-day
compilers (gcc, clang, icc), and it was also not the case for the
historic compilers that I have been able to get a hold of (thanks Matt
Godbolt).
All compiler included in my research either produced correct
DW_AT_ranges or .debug_aranges entries, or they produced no DW_AT_hi/lo
pc at all. The detailed findings are:
- gcc >= 4.4: produces DW_AT_ranges and .debug_aranges
- 4.1 <= gcc < 4.4: no DW_AT_ranges, no DW_AT_high_pc, .debug_aranges
present. The upper version range here is uncertain as godbolt.org does
not have intermediate versions.
- gcc < 4.1: no versions on godbolt.org
- clang >= 3.5: produces DW_AT_ranges, and (optionally) .debug_aranges
- 3.4 <= clang < 3.5: no DW_AT_ranges, no DW_AT_high_pc, .debug_aranges
present.
- clang <= 3.3: no DW_AT_ranges, no DW_AT_high_pc, no .debug_aranges
- icc >= 16.0.1: produces DW_AT_ranges
- icc < 16.0.1: no functional versions on godbolt.org (some are present
but fail to compile)
Based on this analysis, I believe it is safe to start trusting
DW_AT_low/high_pc information in dwarf as well as remove the code for
manually reconstructing range information by traversing the DIE
structure, and just keep the line table fallback. The only compilers
where this will change behavior are pre-3.4 clangs, which are almost 7
years old now. However, the functionality should remain unchanged
because we will be able to reconstruct this information from the line
table, which seems to be needed for some line-tables-only scenarios
anyway (haven't researched this too much, but at least some compilers
seem to emit DW_AT_ranges even in these situations).
In addition, benchmarks showed that for these compilers computing the
ranges via line tables is noticably faster than doing so via the DIE
tree.
Other advantages include simplifying the code base, removing some
untested code (the only test changes are recent tests with overly
reduced synthetic dwarf), and increasing llvm convergence.
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D78489
Originally committed as 416fa7720e30750939c53935051c6c750dfad2c2
Reverted (due to buildbot failure - breaking lldb) in 7a45aeacf3a23449039ef2efcf476995ae1c7007.
I still can't seem to build lldb locally, but Pavel Labath has kindly
provided a potential fix to preserve the old behavior in lldb by
registering a simple recoverable error handler there that prints to the
desired stream in lldb, rather than stderr.
The CMakeLists.txt had a typo which meant that check-lldb-repro was
capturing twice instead of capturing and then replaying. This also
uncovered a missing import in lldb-repro.py. This patch fixes both
issues.
Summary:
This patch deletes the lldb location list parser and teaches the
DWARFExpression class to use the parser in llvm instead. I have
centralized all the places doing the parsing into a single
GetLocationExpression function.
In theory the the actual location list parsing should be covered by llvm
tests, and this glue code by our existing location list tests, but since
we don't have that many location list tests, I've tried to extend the
coverage a bit by adding some explicit dwarf5 loclist handling and a
test of the dumping code.
For DWARF4 location lists this should be NFC (modulo small differences
in error handling which should only show up on invalid inputs). In case
of DWARF5, this fixes various missing bits of functionality, most
notably, the lack of support for DW_LLE_offset_pair.
Reviewers: JDevlieghere, aprantl, clayborg
Subscribers: lldb-commits, dblaikie
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D71003
The DWARFExpression is parsing the location lists in about five places.
Of those, only one actually had proper support for base address
selection entries.
Since r374600, llvm has started to produce location expressions with
base address selection entries more aggresively, which caused some tests
to fail.
This patch adds support for these entries to the places which had it
missing, fixing the failing tests. It also adds a targeted test for the
two of the three fixes, which should continue testing this functionality
even if the llvm output changes. I am not aware of a way to write a
targeted test for the third fix (DWARFExpression::Evaluate).
llvm-svn: 374769
LLDB has three major testing strategies: unit tests, tests that exercise
the SB API though dotest.py and what we currently call lit tests. The
later is rather confusing as we're now using lit as the driver for all
three types of tests. As most of this grew organically, the directory
structure in the LLDB repository doesn't really make this clear.
The 'lit' tests are part of the root and among these tests there's a
Unit and Suite folder for the unit and dotest-tests. This layout makes
it impossible to run just the lit tests.
This patch changes the directory layout to match the 3 testing
strategies, each with their own directory and their own configuration
file. This means there are now 3 directories under lit with 3
corresponding targets:
- API (check-lldb-api): Test exercising the SB API.
- Shell (check-lldb-shell): Test exercising command line utilities.
- Unit (check-lldb-unit): Unit tests.
Finally, there's still the `check-lldb` target that runs all three test
suites.
Finally, this also renames the lit folder to `test` to match the LLVM
repository layout.
Differential revision: https://reviews.llvm.org/D68606
llvm-svn: 374184
