This might affect us. Do we handle it correctly?
I believe we are good, but it would be good to verify via testing once a compiler becomes available.
Greg
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
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
-Tim
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
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.
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@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
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?
Yes, these programs set up an expected state, and the python testsuite uses
the lldb is used to debug these inferiors.
So it looks like we want two scenarios:
Scenario 1: build ToT lldb + llvm/clang/etc using Xcode toolchain; build
test programs AND inferiors using Xcode toolchain
Scenario 2: build ToT lldb + llvm/clang/etc using ToT compiler; build test
programs AND inferiors using ToT compiler
Does that sound right?
S1 is _nearly_ what we have now; it would only require modifying the python
test suite to build inferiors with the system compiler.
I can start looking at what's required to start S2. We've got some hardware
coming to make it easier to bring up.
-Tim
If so, then on check-in we should possibly see some difference on some bot
I’d think so. It makes sure that current lldb is going to continue to work with both new compilers as well as existing compilers and that current lldb is buildable with both current compilers and newer compilers.
Thanks!
-eric
Our buildbot <http://lab.llvm.org:8011/builders/lldb-x86_64-ubuntu-14.04-cmake>
runs the test suite with a selection of compilers, one of which is
clang ToT (test3, test4). You should get an email from it if anything
breaks.
pl
Got it, thanks!
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.
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
Building LLDB with cmake is already supported on all operating systems (including Darwin) for a while so that shouldn’t be a blocker.
Building LLDB with cmake is already supported on all operating systems (including Darwin) for a while so that shouldn’t be a blocker.
While this is technically true, the LLDB test suite makes a lot of assumptions that if you’re on Darwin you built with Xcode, which results in lots of tests not executing at all.
-Chris