> On Mar 19, 2016, at 4:30 PM, Vedant Kumar <[email protected]> wrote:
>
>
>> On Mar 19, 2016, at 12:05 PM, ChrisBieneman <[email protected]> wrote:
>>
>> [Adding Vedant directly]
>>
>> I'm not super familiar with the swift build scripts, but I have a theory of
>> what is going wrong. I think the problem is that compiler-rt is being built
>> during the cross build, and it really shouldn't be.
>>
>> The compiler-rt build system has some significant flaws, and it is being
>> reworked to resolve them. The problem causing this is that we have a hacked
>> up CMake build process that generates multiple cross-targeted binaries from
>> a single build configuration. I believe that compiler-rt's built-in hacky
>> cross-targeting is tripping over however swift is supporting
>> cross-targeting, and it is falling over.
>>
>> With the current state of compiler-rt the right way to build it for Darwin
>> is to treat it as host content, and it will build the Darwin-cross libraries
>> too. Then you can pull the cross-libraries out and put them into the device
>> build.
>
> Could you elaborate on what it means to treat it as host content?
I don't know the exact details of how swift's build scripts work, but I assume
it isn't that different from how you generally would cross-compile a compiler
and runtimes.
For example, if I wanted to build clang for iOS, the first thing I would do is
build a host-capable clang that could target iOS. That clang is then be used to
build the cross-targeted clang and corresponding runtimes. I assume swift does
something similar to solve version incompatibilities between the host compiler
and the target.
Compiler-RT's build system is really screwy for a lot of reasons. On Darwin
when you configure compiler-rt it tries to generate a single build tree that
can target every Darwin-based platform. The logic around that gets really
tripped up if you start trying to treat it as a cross-compile (even though it
really is). This is something I'm working to fix.
The correct way to build compiler-rt on Darwin is to build it in-tree as part
of the host LLVM. If you're building a full host clang you can use the
LLVM_BUILD_EXTERNAL_COMPILER_RT option to enable using the just-built clang.
You can set COMPILER_RT_ENABLE_{platform} and it should be fine.
When you build the cross-targeted tools and libraries, you'll want to disable
building compiler-rt by setting LLVM_TOOL_COMPILER_RT_BUILD=Off. After the
cross-build completes you'll need to pull the clang_rt libraries out of the
host build directory into the target compiler's build directory.
Hopefully I'll have this all re-worked in LLVM sometime in the next couple
months, then it will all change all over again :-).
-Chris
>
> Is setting COMPILER_RT_HOST_TRIPLE and disabling
> COMPILER_RT_ENABLE_{I,TV,WATCH}OS the right thing to do?
>
>
>> Vedant, if you have questions feel free to swing by my office on Monday.
>
> Will do.
>
>
> thanks,
> vedant
>
>> -Chris
>>
>>> On Mar 19, 2016, at 10:11 AM, Andrew Hyatt via swift-dev
>>> <[email protected]> wrote:
>>>
>>> (From /u/thegreatbeanz on reddit.com/r/swift)
>>>
>>> So the problem here is actually that something has gone horribly wrong when
>>> configuring compiler- rt.
>>> You'll notice in the clang commands that it is building in this directory:
>>> clang_rt.builtins_armv7_10.4.dir
>>> What that means is it is building the clang_rt.10.4 archive which provides
>>> back ported library functions to OS X 10.4. Obviously 10.4 didn't support
>>> armv7 as an architecture, something has gone really wrong here.
>>> If you're on the latest swift it is probably a regression caused by
>>> 53f48f8. You need to email swift-dev to get support from Dmitri Gribenko
>>> and Vedant Kumar.
>>> Source: I wrote most of the compiler-rt builtin build system for Darwin.
>>>
>>> Andrew Hyatt
>>> [email protected]
>>>
>>>> On Mar 19, 2016, at 9:26 AM, Andrew Hyatt via swift-dev
>>>> <[email protected]> wrote:
>>>>
>>>> Building swift-llvm fails when using build-script to cross compile because
>>>> build-script wrongly gives duplicate -isysroot arguments.
>>>>
>>>> The full arguments that are given to clang by build-script while building
>>>> LLVM are here: https://gist.github.com/ahyattdev/8ecc5d3808b9ee543a60
>>>>
>>>> The command I use to build the compiler, using the latest sources from
>>>> GitHub
>>>>
>>>> utils/build-script -R -i -- --cross-compile-tools-deployment-targets
>>>> "iphoneos-arm64 iphoneos-armv7 iphoneos-armv7s"
>>>> --user-config-args="-DLLVM_ENABLE_BACKTRACES=Off"
>>>>
>>>> This error occurs after the phase of building llvm for the host machine,
>>>> and occurs during the cross compilation phase.
>>>>
>>>> Andrew Hyatt
>>>> [email protected]
>>>>
>>>> _______________________________________________
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>>>> https://lists.swift.org/mailman/listinfo/swift-dev
>>>
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>
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