r228253 - [PowerPC] Revert workaround for TLS linker bug

[Bill Schmidt]

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.

Details to follow.

Bill