[Flang] Implicitly add clang if flang enabled. #123964
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cor3ntin
added
cmake
ldionne
approved these changes
Jan 27, 2025
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I would like this but I think some downstreams don't depend on the clang-based driver so might have objections. The difference between this/flang-rt and e.g. clang not adding other things is that clang can use alternatives for all of its dependencies, and does by default on most platforms. There's no alternative runtime to |
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If some downstreams don't need Clang, how do they build Flang? CMake currently aborts with FATAL_ERROR. If you try a standalone build, you get: |
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Not sure; I'm not involved personally in any downstream that doesn't use the clang-based driver. I just remember this as the justification previously that we add |
You may still compile the runtime separately, using a standalone build, or you don't even need it for the host platform, only for the target platform (cross-compile). In either case, you need a workaround to not add "flang-rt" implicitly. There isn't one for "clang" and it seems nobody requested one. The position
feels inconsistent to me. |
petrhosek
approved these changes
Feb 6, 2025
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I agree. I personally think it should all be added implicitly, with flags for not doing so. |
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That or the cmake should be fixed so that we don't need clang to be in ENABLE_PROJECTS. We don't actually need all of clang, just specific driver stuff that could be built as dependencies in the cmake without requiring clang in its entirety. |
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How does this work when using a pre-built clang (say for a matching version and/or commit)? We need a way to build flang independently of clang, not least because of resource constraints. |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/59/builds/14954 Here is the relevant piece of the build log for the reference |
This has already been discussed in this thread. If you don't add |
Meinersbur
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Mar 26, 2025
Remove the FLANG_INCLUDE_RUNTIME option which was replaced by LLVM_ENABLE_RUNTIMES=flang-rt. The FLANG_INCLUDE_RUNTIME option was added in #122336 which disables the non-runtimes build instructions for the Flang runtime so they do not conflict with the LLVM_ENABLE_RUNTIMES=flang-rt option added in #110217. In order to not maintain multiple build instructions for the same thing, this PR completely removes the old build instructions (effectively forcing FLANG_INCLUDE_RUNTIME=OFF). As per discussion in https://discourse.llvm.org/t/buildbot-changes-with-llvm-enable-runtimes-flang-rt/83571/2 we now implicitly add LLVM_ENABLE_RUNTIMES=flang-rt whenever Flang is compiled in a bootstrapping (non-standalone) build. Because it is possible to build Flang-RT separately, this behavior can be disabled using `-DFLANG_ENABLE_FLANG_RT=OFF`. Also see the discussion an implicitly adding runtimes/projects in #123964.
Meinersbur
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Apr 30, 2025
This reverts commit 27539c3. Retry with new buildbot configuration after master restart. Original message: Remove the FLANG_INCLUDE_RUNTIME option which was replaced by LLVM_ENABLE_RUNTIMES=flang-rt. The FLANG_INCLUDE_RUNTIME option was added in #122336 which disables the non-runtimes build instructions for the Flang runtime so they do not conflict with the LLVM_ENABLE_RUNTIMES=flang-rt option added in #110217. In order to not maintain multiple build instructions for the same thing, this PR completely removes the old build instructions (effectively forcing FLANG_INCLUDE_RUNTIME=OFF). As per discussion in https://discourse.llvm.org/t/buildbot-changes-with-llvm-enable-runtimes-flang-rt/83571/2 we now implicitly add LLVM_ENABLE_RUNTIMES=flang-rt whenever Flang is compiled in a bootstrapping (non-standalone) build. Because it is possible to build Flang-RT separately, this behavior can be disabled using `-DFLANG_ENABLE_FLANG_RT=OFF`. Also see the discussion an implicitly adding runtimes/projects in #123964.
IanWood1
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May 6, 2025
This reverts commit 27539c3. Retry with new buildbot configuration after master restart. Original message: Remove the FLANG_INCLUDE_RUNTIME option which was replaced by LLVM_ENABLE_RUNTIMES=flang-rt. The FLANG_INCLUDE_RUNTIME option was added in llvm#122336 which disables the non-runtimes build instructions for the Flang runtime so they do not conflict with the LLVM_ENABLE_RUNTIMES=flang-rt option added in llvm#110217. In order to not maintain multiple build instructions for the same thing, this PR completely removes the old build instructions (effectively forcing FLANG_INCLUDE_RUNTIME=OFF). As per discussion in https://discourse.llvm.org/t/buildbot-changes-with-llvm-enable-runtimes-flang-rt/83571/2 we now implicitly add LLVM_ENABLE_RUNTIMES=flang-rt whenever Flang is compiled in a bootstrapping (non-standalone) build. Because it is possible to build Flang-RT separately, this behavior can be disabled using `-DFLANG_ENABLE_FLANG_RT=OFF`. Also see the discussion an implicitly adding runtimes/projects in llvm#123964.
IanWood1
pushed a commit
to IanWood1/llvm-project
that referenced
this pull request
May 6, 2025
This reverts commit 27539c3. Retry with new buildbot configuration after master restart. Original message: Remove the FLANG_INCLUDE_RUNTIME option which was replaced by LLVM_ENABLE_RUNTIMES=flang-rt. The FLANG_INCLUDE_RUNTIME option was added in llvm#122336 which disables the non-runtimes build instructions for the Flang runtime so they do not conflict with the LLVM_ENABLE_RUNTIMES=flang-rt option added in llvm#110217. In order to not maintain multiple build instructions for the same thing, this PR completely removes the old build instructions (effectively forcing FLANG_INCLUDE_RUNTIME=OFF). As per discussion in https://discourse.llvm.org/t/buildbot-changes-with-llvm-enable-runtimes-flang-rt/83571/2 we now implicitly add LLVM_ENABLE_RUNTIMES=flang-rt whenever Flang is compiled in a bootstrapping (non-standalone) build. Because it is possible to build Flang-RT separately, this behavior can be disabled using `-DFLANG_ENABLE_FLANG_RT=OFF`. Also see the discussion an implicitly adding runtimes/projects in llvm#123964.
IanWood1
pushed a commit
to IanWood1/llvm-project
that referenced
this pull request
May 6, 2025
This reverts commit 27539c3. Retry with new buildbot configuration after master restart. Original message: Remove the FLANG_INCLUDE_RUNTIME option which was replaced by LLVM_ENABLE_RUNTIMES=flang-rt. The FLANG_INCLUDE_RUNTIME option was added in llvm#122336 which disables the non-runtimes build instructions for the Flang runtime so they do not conflict with the LLVM_ENABLE_RUNTIMES=flang-rt option added in llvm#110217. In order to not maintain multiple build instructions for the same thing, this PR completely removes the old build instructions (effectively forcing FLANG_INCLUDE_RUNTIME=OFF). As per discussion in https://discourse.llvm.org/t/buildbot-changes-with-llvm-enable-runtimes-flang-rt/83571/2 we now implicitly add LLVM_ENABLE_RUNTIMES=flang-rt whenever Flang is compiled in a bootstrapping (non-standalone) build. Because it is possible to build Flang-RT separately, this behavior can be disabled using `-DFLANG_ENABLE_FLANG_RT=OFF`. Also see the discussion an implicitly adding runtimes/projects in llvm#123964.
GeorgeARM
pushed a commit
to GeorgeARM/llvm-project
that referenced
this pull request
May 7, 2025
This reverts commit 27539c3. Retry with new buildbot configuration after master restart. Original message: Remove the FLANG_INCLUDE_RUNTIME option which was replaced by LLVM_ENABLE_RUNTIMES=flang-rt. The FLANG_INCLUDE_RUNTIME option was added in llvm#122336 which disables the non-runtimes build instructions for the Flang runtime so they do not conflict with the LLVM_ENABLE_RUNTIMES=flang-rt option added in llvm#110217. In order to not maintain multiple build instructions for the same thing, this PR completely removes the old build instructions (effectively forcing FLANG_INCLUDE_RUNTIME=OFF). As per discussion in https://discourse.llvm.org/t/buildbot-changes-with-llvm-enable-runtimes-flang-rt/83571/2 we now implicitly add LLVM_ENABLE_RUNTIMES=flang-rt whenever Flang is compiled in a bootstrapping (non-standalone) build. Because it is possible to build Flang-RT separately, this behavior can be disabled using `-DFLANG_ENABLE_FLANG_RT=OFF`. Also see the discussion an implicitly adding runtimes/projects in llvm#123964.
Ankur-0429
pushed a commit
to Ankur-0429/llvm-project
that referenced
this pull request
May 9, 2025
This reverts commit 27539c3. Retry with new buildbot configuration after master restart. Original message: Remove the FLANG_INCLUDE_RUNTIME option which was replaced by LLVM_ENABLE_RUNTIMES=flang-rt. The FLANG_INCLUDE_RUNTIME option was added in llvm#122336 which disables the non-runtimes build instructions for the Flang runtime so they do not conflict with the LLVM_ENABLE_RUNTIMES=flang-rt option added in llvm#110217. In order to not maintain multiple build instructions for the same thing, this PR completely removes the old build instructions (effectively forcing FLANG_INCLUDE_RUNTIME=OFF). As per discussion in https://discourse.llvm.org/t/buildbot-changes-with-llvm-enable-runtimes-flang-rt/83571/2 we now implicitly add LLVM_ENABLE_RUNTIMES=flang-rt whenever Flang is compiled in a bootstrapping (non-standalone) build. Because it is possible to build Flang-RT separately, this behavior can be disabled using `-DFLANG_ENABLE_FLANG_RT=OFF`. Also see the discussion an implicitly adding runtimes/projects in llvm#123964.
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Clang is required to compile Flang. Instead of erroring-out if Clang is enabled, for convinience implicitly add it to
LLVM_ENABLE_PROJECTS, consistent with how the MLIR dependency is handled.This is mainly intended as a discussion about whether
LLVM_ENABLE_RUNTIMES=flang-rt(#110217) is to be enabled implicitly as well (https://discourse.llvm.org/t/buildbot-changes-with-llvm-enable-runtimes-flang-rt/83571/2). If yes, not implicitly enabling Clang would be inconsistent with how the MLIR and flang-rt dependency are enforced.I'd prefer to not do so implicitly:
LLVM_ENABLE_PROJECTS and LLVM_ENABLE_RUNTIMES are user-controlled. Overwriting them takes away from their decision. I would expect to have only those projects/runtimes to be built that I have specified.
The global variable LLVM_ENABLE_PROJECTS and the CMakeCache.txt entry for LLVM_ENABLE_PROJECTS are different entities. How it is implemented, the global LLVM_ENABLE_PROJECTS shadows the cache entry, so they have two different values. This adds to confusion. Overwriting the cache value with
FORCEoption would cause CMake to re-run a second time. Better get it right the first time.The buildbots use the settings
depends_on_projects=[..](which the values ofLLVM_ENABLE_PROJECTSandLLVM_ENABLE_RUNTIMESis derived from). Ifclang,mlir, orflang-rtis not specified there, the buildbot will not trigger a rebuild if files in those directories have been changed.For
LLVM_ENABLE_RUNTIMES, including flang-rt, it is possible to build the runtime separately/out-of-tree/standalone, or not for the default target for whatever reason, in which case the implicit addition ofLLVM_ENABLE_RUNTIMES=flang-rtmust be again disabled somehow. This adds to the complexity to the build system.LLVM_ENABLE_PROJECTS=clangalso does not implicitly add any project/runtime that is technically required for a complete toolchain, such aslld,compiler-rt,libc,libcxx,libcxxabi,unwind.