llvm dev - Jul 2016 - Simple program fails to compile depending on target os

Thanks!

I also found test/CodeGen/ARM/ghc-tcreturn-lowered.ll, which tests only for
thumbv7-eabi,
so, i tried a few more variations:

[x] arm64-apple-ios
[x] arm64-apple-ios7.0.0
[x] arm64-apple-darwin
[x] armv7-apple
[x] thumbv7-apple
[x] thumbv7-apple-darwin
[x] i386-apple-ios
[x] i386-apple-darwin

[f] thumbv7-apple-ios
[f] thumbv7-apple-ios7.0.0
[f] armv7-apple-ios

I’ve also just build a HEAD version (LLVM version 3.9.0svn), and the code in
fact *does*
compile with 3.9.0svn.

Cheers,
 Moritz
> On Jul 4, 2016, at 10:19 AM, Tim Northover <t.p.northover at
gmail.com> wrote:
> 
> On 3 July 2016 at 18:26, Moritz Angermann via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>> Any hints as to why this code only compiles for darwin and not for ios,
would be greatly appreciated.
> 
> I saw the same thing on a checkout from a few months back, but I then
> updated and ToT seems to get it right (well, slightly different
> CodeGen because the iOS linker only started supporting tail calls at
> 5.0 or something so -darwin doesn't use them, but both compiled to
> correct code). There's certainly been some churn in this bit of code
> recently, so the bug was probably fixed incidentally as part of that.
> 
> Tim.

On 3 July 2016 at 19:51, Moritz Angermann <moritz.angermann at gmail.com>
wrote:
> I’ve also just build a HEAD version (LLVM version 3.9.0svn), and the code
in fact *does*
> compile with 3.9.0svn.
So, just to be clear, your list was from a slightly older version and
we might not have anything to worry about? Otherwise I'm happy to help
digging.

Cheers.

Tim.

>> I would however suggest to add -mtriple=armv7-apple-ios and
-mtriple=armv7-apple-darwin
>> to the test in test/CodeGen/ARM/ghc-tcreturn-lowered.ll, so that
potential regressions,
>> as found.
> 
> The "-darwin" triple shouldn't really be used. Actually,
I'm not sure
> why it even exists: it could produce pretty much anything without
> anyone inside Apple caring as part of their day job.
> 
> I'm happy to add tests, but personally I'd suggest
> "thumbv7-apple-ios7.0" and "armv7-apple-ios7.0" as the
triples (iOS
> 7.0 is a reasonable baseline). But I'd also suggest GHC uses
> "thumbv7-apple-iosN". It's likely to be more performant than
"armv7"
> and is certainly a lot more tested (as the Clang default).
That’s the one I stated out to begin with. Currently ghc, uses
armv7-apple-darwin10, which however generates:

     warning: .macosx_version_min should only be used for macosx targets
            .macosx_version_min 10, 0

this triple that produces usable libs though. (thumbv7-apple-darwin10 does
compile, however the produced library fails to work properly, which is likely
a separate ghc bug).

I’ll see that ghc used x86_64-apple-macosx10 for macOS builds then instead
of the current x86_64-apple-darwin10.0.0.

In the interim I don’t see a way around armv7-apple-darwin10 for the armv7
builds, as it crashes llc until 3.9 otherwise. For arm64, we’ll use
arm64-apple-ios7.0.0.

Any further suggestions are welcome!

Cheers,
 Moritz