r228253 - [PowerPC] Revert workaround for TLS linker bug
Bill Schmidt
wschmidt at linux.vnet.ibm.com
Thu Feb 5 17:13:44 PST 2015
On Thu, 2015-02-05 at 18:52 -0600, Bill Schmidt wrote:
> On Wed, 2015-02-04 at 18:30 -0800, Chandler Carruth wrote:
> >
> > On Wed, Feb 4, 2015 at 5:12 PM, Bill Schmidt
> > <wschmidt at linux.vnet.ibm.com> wrote:
> > Author: wschmidt
> > Date: Wed Feb 4 19:12:24 2015
> > New Revision: 228253
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=228253&view=rev
> > Log:
> > [PowerPC] Revert workaround for TLS linker bug
> >
> > In r227480, Ulrich Weigand introduced a workaround for a
> > linker
> > optimization bug that can create mis-optimized code for
> > accesses to
> > general-dynamic or local-dynamic TLS variables. The linker
> > optimization bug only occurred for Clang/LLVM because of some
> > inefficient code being generated for these TLS accesses. I
> > have
> > recently corrected LLVM to produce the efficient code sequence
> > expected by the linkers, so this workaround is no longer
> > needed.
> > Therefore this patch reverts r227480.
> >
> > I've tested that the previous bootstrap failure no longer
> > occurs with
> > the workaround reverted.
> >
> > This is awesome Bill, thanks again for tackling all of this.
>
> Well, unfortunately it isn't going to stick. :(
>
> A bootstrap with -O3 still fails, and there is a further, different, and
> more horrible linker optimization error to blame. I'm going to
> re-disable the linker optimizations for now. I'm unwilling to handcuff
> the compiler as much as would be required to let the linker optimization
> operate in its present state.
Correction: Still too soon to blame the linker here. My eyes were
playing tricks on me. Will take a fresh look at the cause of the
bootstrap error in the morning.
Bill
>
> Details to follow.
>
> Bill
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