[Orc] Let LLJIT default to JITLink for ELF-based ARM targets

[weliveindetail]

Over the last weeks, I have landed a number of patches to JITLink's AArch32 backend to reach feature-parity with RuntimeDyld for ELF:

9577806b1e6c [JITLink][AArch32] Implement R_ARM_PREL31 and process .ARM.exidx sections (#79044)
e5ca202ef887 [JITLink][AArch32] Multi-stub support for armv7/thumbv7 (#78371)
2bb6d7b8a4d1 [clang-repl] Limit use of PLT offset flag to linkers that support it
565470ed2713 [JITLink][AArch32] Implement ELF relocation R_ARM_NONE
bfb09326be22 [JITLink][AArch32] Implement ELF relocation R_ARM_TARGET1
4821c90c24d5 [clang-repl] Fix PLT offset too large linker error on ARM (#78959)
c4fc563b8d41 [JITLink][AArch32] Add GOT builder and implement R_ARM_GOT_PREL relocations for ELF (#78753)
6a433d77b1f4 [llvm-jitlink] Allow optional stub-kind filter in stub_addr() expressions (#78369)
01ba627f431c [llvm-jitlink] Refactor GOT and stubs registration (NFC) (#78365)
9c607e77eae7 [JITLink][AArch32] Refactor StubsManager (NFC)

This allows us to run clang-repl on armv7 and use all the features we had with RuntimeDyld before. All existing tests for clang-repl are passing.

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[weliveindetail]

There is one more review open that aims to extend support to non-v7 targets: #79082

[vgvassilev]

Pretty nice! This lgtm but I’d wait for Lang.

[weliveindetail]

Double-checked on armv7 (32-bit Raspbian on RPi 3b) with all commits landed:

$ cat CMakeCache.txt | grep HOST_TRIPLE
LLVM_HOST_TRIPLE:STRING=arm-linux-gnueabihf

Tests run fine:

$ bin/llvm-lit --filter=Interpreter tools/clang/test
-- Testing: 22 of 18430 tests, 4 workers --
PASS: Clang :: Interpreter/execute-stmts.cpp (1 of 22)
PASS: Clang :: Interpreter/inline-virtual.cpp (2 of 22)
PASS: Clang :: Interpreter/execute.cpp (3 of 22)
PASS: Clang :: Interpreter/const.cpp (4 of 22)
PASS: Clang :: Interpreter/multiline.cpp (5 of 22)
PASS: Clang :: Interpreter/code-undo.cpp (6 of 22)
PASS: Clang :: Interpreter/global-dtor.cpp (7 of 22)
PASS: Clang :: Interpreter/lambda.cpp (8 of 22)
PASS: Clang :: Interpreter/execute-weak.cpp (9 of 22)
XFAIL: Clang :: Interpreter/simple-exception.cpp (10 of 22)
PASS: Clang :: Interpreter/disambiguate-decl-stmt.cpp (11 of 22)
PASS: Clang :: Interpreter/sanity.c (12 of 22)
UNSUPPORTED: Clang :: Interpreter/plugins.cpp (13 of 22)
UNSUPPORTED: Clang :: Interpreter/dynamic-library.cpp (14 of 22)
UNSUPPORTED: Clang :: Interpreter/CUDA/device-function-template.cu (15 of 22)
UNSUPPORTED: Clang :: Interpreter/CUDA/host-and-device.cu (16 of 22)
UNSUPPORTED: Clang :: Interpreter/CUDA/sanity.cu (17 of 22)
UNSUPPORTED: Clang :: Interpreter/CUDA/device-function.cu (18 of 22)
UNSUPPORTED: Clang :: Interpreter/CUDA/memory.cu (19 of 22)
PASS: Clang :: Interpreter/fail.cpp (20 of 22)
PASS: Clang :: Interpreter/stmt-serialization.cpp (21 of 22)
PASS: Clang :: Interpreter/incremental-mode.cpp (22 of 22)

Testing Time: 15.51s

Total Discovered Tests: 18430
  Excluded         : 18408 (99.88%)
  Unsupported      :     7 (0.04%)
  Passed           :    14 (0.08%)
  Expectedly Failed:     1 (0.01%)

1 warning(s) in tests

This is using JITLink::

$ cat ../clang/test/Interpreter/inline-virtual.cpp | bin/clang-repl -Xcc -fno-rtti --debug-only=jitlink 2>&1 | grep aarch32 | head -3
    Created Arm entry for __cxa_begin_catch in __llvm_jitlink_aarch32_STUBS_v7: 0x0 (block + 0x00000000): size: 0x0000000c, linkage: strong, scope: local, dead  -   <anonymous symbol>
    Using Arm entry 0x0 (block + 0x00000000): size: 0x0000000c, linkage: strong, scope: local, dead  -   <anonymous symbol> in __llvm_jitlink_aarch32_STUBS_v7
    Created Arm entry for _ZSt9terminatev in __llvm_jitlink_aarch32_STUBS_v7: 0x0 (block + 0x00000000): size: 0x0000000c, linkage: strong, scope: local, dead  -   <anonymous symbol>

[weliveindetail]

Test working as well with armv6 target:

$ bin/llvm-lit --filter=Interpreter tools/clang/test
-- Testing: 22 of 18430 tests, 4 workers --
PASS: Clang :: Interpreter/lambda.cpp (1 of 22)
PASS: Clang :: Interpreter/execute-stmts.cpp (2 of 22)
PASS: Clang :: Interpreter/execute.cpp (3 of 22)
PASS: Clang :: Interpreter/const.cpp (4 of 22)
PASS: Clang :: Interpreter/fail.cpp (5 of 22)
PASS: Clang :: Interpreter/execute-weak.cpp (6 of 22)
PASS: Clang :: Interpreter/code-undo.cpp (7 of 22)
XFAIL: Clang :: Interpreter/simple-exception.cpp (8 of 22)
PASS: Clang :: Interpreter/global-dtor.cpp (9 of 22)
PASS: Clang :: Interpreter/inline-virtual.cpp (10 of 22)
PASS: Clang :: Interpreter/disambiguate-decl-stmt.cpp (11 of 22)
PASS: Clang :: Interpreter/stmt-serialization.cpp (12 of 22)
UNSUPPORTED: Clang :: Interpreter/dynamic-library.cpp (13 of 22)
UNSUPPORTED: Clang :: Interpreter/plugins.cpp (14 of 22)
UNSUPPORTED: Clang :: Interpreter/CUDA/device-function.cu (15 of 22)
UNSUPPORTED: Clang :: Interpreter/CUDA/memory.cu (16 of 22)
UNSUPPORTED: Clang :: Interpreter/CUDA/device-function-template.cu (17 of 22)
UNSUPPORTED: Clang :: Interpreter/CUDA/sanity.cu (18 of 22)
UNSUPPORTED: Clang :: Interpreter/CUDA/host-and-device.cu (19 of 22)
PASS: Clang :: Interpreter/multiline.cpp (20 of 22)
PASS: Clang :: Interpreter/incremental-mode.cpp (21 of 22)
PASS: Clang :: Interpreter/sanity.c (22 of 22)

Testing Time: 22.43s

Total Discovered Tests: 18430
  Excluded         : 18408 (99.88%)
  Unsupported      :     7 (0.04%)
  Passed           :    14 (0.08%)
  Expectedly Failed:     1 (0.01%)

1 warning(s) in tests

This is using the pre-v7 config:

$ cat ../clang/test/Interpreter/inline-virtual.cpp | bin/clang-repl -Xcc -fno-rtti --debug-only=jitlink 2>&1 | grep aarch32 | head -3
    Created __llvm_jitlink_aarch32_STUBS_prev7 entry for __cxa_begin_catch: 0x0 (block + 0x00000000): size: 0x00000008, linkage: strong, scope: local, dead  -   <anonymous symbol>
    Using __llvm_jitlink_aarch32_STUBS_prev7 entry 0x0 (block + 0x00000000): size: 0x00000008, linkage: strong, scope: local, dead  -   <anonymous symbol>
    Created __llvm_jitlink_aarch32_STUBS_prev7 entry for _ZSt9terminatev: 0x0 (block + 0x00000000): size: 0x00000008, linkage: strong, scope: local, dead  -   <anonymous symbol>

[lhames]

LGTM. This is a really impressive result for the JITLink ELF/AArch32 backend -- thanks for all of your hard work on it @weliveindetail and @eymay!

[weliveindetail]

Thanks for all the help with the reviews. I will keep an eye on the build bots and follow up with any potential issues.