[llvm-dev] (Thin)LTO llvm build

[Teresa Johnson via llvm-dev]

On Fri, Sep 16, 2016 at 1:48 PM, Carsten Mattner <carstenmattner at gmail.com>
wrote:

> On Fri, Sep 16, 2016 at 10:18 PM, Teresa Johnson <tejohnson at google.com>
> wrote:
> >
> > Cc'ing llvm-dev again in case someone knows what is going on.
> >
> > That error is coming from a polly configure script, which I don't
> > have cloned into my own tree. Not sure why polly would behave
> > differently when configuring for ThinLTO. Does polly configure ok
> > when configuring the same way, but for regular LTO?
>
> Yes it does, and I don't remember when I've added it, meaning it's
> been working when bootstrapping llvm with the host gcc toolchain, for
> a long time.
>

You mentioned in your original email:
> I first tried to rebuild llvm with llvm-3.9, which has ThinLTO, by
> providing -DLLVM_ENABLE_LTO=Thin, but that failed very quickly, so I
> fell back to building with -DLLVM_ENABLE_LTO=On and using the system
> CC/CXX (gcc 6.1).

I assume this error when you try to bootstrap using llvm-3.9 and ThinLTO
then? What about bootstrapping with llvm-3.9 and -DLLVM_ENABLE_LTO=On?

If the latter works, I'll have to clone polly and see if I can reproduce it
and see what is different between a -DLLVM_ENABLE_LTO=Thin
and -DLLVM_ENABLE_LTO=On build then.

Teresa


> > On Fri, Sep 16, 2016 at 12:36 PM, Carsten Mattner <
> carstenmattner at gmail.com> wrote:
> > >
> > > Hi Teresa,
> > >
> > > I've just attempted a THIN_LTO build again, and the
> > > error I ran into is as follows, and happens during
> > > cmake. I'm explicitly telling cmake to us llvm-ar and llvm-ranlib
> > > as suggested.
> > >
> > > [...]
> > > -- Performing Test COMPILER_RT_HAS_STATIC_FLAG - Success
> > > -- Performing Test COMPILER_RT_SUPPORTS_ATOMIC_KEYWORD
> > > -- Performing Test COMPILER_RT_SUPPORTS_ATOMIC_KEYWORD - Success
> > > -- Builtin supported architectures:
> > > -- ISL version: isl-0.17.1-164-gcbba1b6
> > > -- Performing Test HAS_ATTRIBUTE_WARN_UNUSED_RESULT
> > > -- Performing Test HAS_ATTRIBUTE_WARN_UNUSED_RESULT - Failed
> > > -- Performing Test HAVE___ATTRIBUTE__
> > > -- Performing Test HAVE___ATTRIBUTE__ - Failed
> > > -- Performing Test HAVE_DECL_FFS
> > > -- Performing Test HAVE_DECL_FFS - Failed
> > > -- Performing Test HAVE_DECL___BUILTIN_FFS
> > > -- Performing Test HAVE_DECL___BUILTIN_FFS - Failed
> > > -- Performing Test HAVE_DECL__BITSCANFORWARD
> > > -- Performing Test HAVE_DECL__BITSCANFORWARD - Failed
> > > CMake Error at tools/polly/lib/External/CMakeLists.txt:90 (message):
> > >   No ffs implementation found
> > > [...]
>



-- 
Teresa Johnson |  Software Engineer |  tejohnson at google.com |  408-460-2413
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