[lldb-dev] llvm changing line table info from DWARF 2 to DWARF 4

Thu Oct 20 13:00:30 PDT 2016

Building LLDB with cmake is already supported on all operating systems
(including Darwin) for a while so that shouldn't be a blocker.

On Thu, Oct 20, 2016 at 8:09 PM Tim Hammerquist via lldb-dev <
lldb-dev at lists.llvm.org> wrote:

> IIRC, the only reason the LLDB python test suite uses the in-tree compiler
> (Scenario 1) was so to test sanitizers before they were available in the
> system compiler. If that's the case, then using Xcode 8 on the builder will
> allow both the LLDB build and tests to use the system compiler.
>
> As I understand it, there are a few ways to go about building lldb using
> the ToT (or at least, last green) compiler. This approach will be of
> limited use until building lldb with cmake is supported, however. I'm
> following up on this timeline.
>
> -Tim
>
>
> On Thu, Oct 20, 2016 at 11:50 AM, Ted Woodward <
> ted.woodward at codeaurora.org> wrote:
>
> I think a hardcoded value of 1 for maximum_operations_per_instruction will
> work like it does today – 1 linetable entry per Hexagon packet, which may
> have 1-4 instructions in it. Hexagon executes 1 packet at a time, so
> anywhere from 1-4 instructions at once.
>
>
>
> At O0, the compiler doesn’t packetize instructions, so 1 instruction is
> run at a time. At 01 it will, but it doesn’t do many other optimizations.
> We should still have 1 line per packet. O2 and O3 can move instructions
> around, so will have up to 4 source lines in 1 packet. I think we’ll need
> to experiment internally with what that means for the debugger, once we get
> this change.
>
>
>
> --
>
> Qualcomm Innovation Center, Inc.
>
> The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
> Linux Foundation Collaborative Project
>
>
>
> *From:* Eric Christopher [mailto:echristo at gmail.com]
> *Sent:* Wednesday, October 19, 2016 6:09 PM
> *To:* Tim Hammerquist <penryu at gmail.com>
> *Cc:* Greg Clayton <gclayton at apple.com>; Ted Woodward <
> ted.woodward at codeaurora.org>; LLDB <lldb-dev at lists.llvm.org>
> *Subject:* Re: [lldb-dev] llvm changing line table info from DWARF 2 to
> DWARF 4
>
>
>
>
>
> On Wed, Oct 19, 2016 at 3:34 PM Tim Hammerquist <penryu at gmail.com> wrote:
>
> I was mistaken.
>
>
>
> The system toolchain builds stage1 llvm, clang & co.
>
> The system toolchain builds lldb containing the llvm/clang/etc bits.
>
> The system toolchain builds gtest test programs.
>
> The stage1 compiler builds the python test inferiors.
>
>
>
>
>
> OK, then it sounds like at least some of the test programs are built with
> the new compiler? IIRC the python test inferiors here are the programs that
> are the meat of the testsuite for lldb yes?
>
>
>
> If so, then on check-in we should possibly see some difference on some bot
> if they all use the same general configuration.  I don't have a current
> checkout so I don't know if the default -g is used or if it's set to a
> different dwarf level. Currently it looks like clang will use dwarf4 by
> default with -g:
>
>
>
> echristo at dzur ~/tmp> ~/builds/build-llvm/bin/clang -c foo.c -o - -target
> x86_64-apple-macosx10.11 -g | llvm-dwarfdump - | grep version | grep -v
> clang
>
> 0x00000000: Compile Unit: length = 0x00000037 version = 0x0004 abbr_offset
> = 0x0000 addr_size = 0x08 (next unit at 0x0000003b)
>
>          version: 2
>
>
>
> where the first line is the debug_info header and the second is the
> version in the line table.
>
>
>
> Ted/Greg: Relatedly, what brought this up was the vliw aspect with maximum_operations_per_instruction
> - it's being hard coded to 1 here and I'm not sure how we want to deal with
> that on hexagon? Currently it'll be hard set to 1 so line stepping will
> work as I imagine it currently does. That said, if we wanted to take
> advantage of it then that's different. Primarily I wasn't sure if Ted and
> folk had a debugger that did take advantage of it if it was there.
>
>
>
> Thanks!
>
>
>
> -eric
>
>
>
>
>
> On Wed, Oct 19, 2016 at 3:28 PM, Eric Christopher <echristo at gmail.com>
> wrote:
>
>
>
> On Wed, Oct 19, 2016 at 3:26 PM Tim Hammerquist <penryu at gmail.com> wrote:
>
> The LLDB job in llvm.org will build a stage1 RA with
> llvm+clang+libcxx+compiler-rt using the system compiler, and use the new
> compiler to build lldb.
>
>
>
> By default, this is kicked off automatically when a clang stage1 RA is
> successful, but can be manually triggered to build HEAD, or any revision
> desired.
>
>
>
> The python test suite (invoked with the xcodebuild target
> lldb-python-test-suite) uses the newly built compiler to build its test
> programs.
>
>
>
>
> http://lab.llvm.org:8080/green/job/lldb_build_test/21202/consoleFull#console-section-4
>
>
>
> However, the gtest suite (target lldb-gtest) uses the system (Xcode
> toolchain) compiler to build test programs.
>
>
>
>
> http://lab.llvm.org:8080/green/job/lldb_build_test/21202/artifact/lldb/test_output.zip
>
>
>
>
>
> This seems like something that should be fixed :)
>
>
>
> -eric
>
>
>
>
>
> -Tim
>
>
>
> On Wed, Oct 19, 2016 at 2:36 PM, Eric Christopher <echristo at gmail.com>
> wrote:
>
> From chatting with Tim it sounds like at least one lldb bot uses the ToT
> compiler - we should probably verify that not only does it use that to
> build lldb but uses it for the tests. That'll get us at least some testing
> here.
>
>
>
> -eric
>
>
>
> On Wed, Oct 19, 2016 at 12:55 PM Greg Clayton via lldb-dev <
> lldb-dev at lists.llvm.org> wrote:
>
> I believe we are good, but it would be good to verify via testing once a
> compiler becomes available.
>
> Greg
>
> > On Oct 19, 2016, at 12:19 PM, Ted Woodward via lldb-dev <
> lldb-dev at lists.llvm.org> wrote:
> >
> > This might affect us. Do we handle it correctly?
> >
> > https://reviews.llvm.org/D16697
> >
> > --
> > Qualcomm Innovation Center, Inc.
> > The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
> Linux Foundation Collaborative Project
> >
> > _______________________________________________
> > lldb-dev mailing list
> > lldb-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
>
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>
>
>
>
> --
>
> Tim <penryu at gmail.com>
>
>
>
>
>
> --
>
> Tim <penryu at gmail.com>
>
>
>
>
> --
> Tim <penryu at gmail.com>
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