[PATCH] D74436: Change clang option -ffp-model=precise to select ffp-contract=on

[Blower, Melanie I via cfe-commits]

I reverted MaskRay's "reland" since the original patch is causing trouble on PowerPC, check-all is passing on my box.  Sorry for the trouble. 

> -----Original Message-----
> From: Andy Kaylor via Phabricator <reviews at reviews.llvm.org>
> Sent: Thursday, February 13, 2020 9:20 PM
> To: Blower, Melanie I <melanie.blower at intel.com>; lebedev.ri at gmail.com;
> rjmccall at gmail.com; sepavloff at gmail.com
> Cc: maskray at google.com; jji at us.ibm.com; david.bolvansky at gmail.com;
> martin at martin.st; Wang, Pengfei <pengfei.wang at intel.com>;
> wuzish at cn.ibm.com; nemanja.i.ibm at gmail.com; kit.barton at gmail.com; cfe-
> commits at lists.llvm.org; mlekena at skidmore.edu; blitzrakete at gmail.com;
> shenhan at google.com; peter.waller at arm.com
> Subject: [PATCH] D74436: Change clang option -ffp-model=precise to select ffp-
> contract=on
> 
> andrew.w.kaylor added a subscriber: MaskRay.
> andrew.w.kaylor added a comment.
> 
> In D74436#1875386 <https://reviews.llvm.org/D74436#1875386>, @thakis
> wrote:
> 
> > The revert of this breaks tests everywhere, as far as I can tell.
> 
> 
> It looks like something strange happened with the revert:
> 
> > clang-11: warning: overriding '-ffp-model=strict' option with '-ffp-
> model=strict' [-Woverriding-t-option]
> 
> I believe the problem is that the original change that was being reverted
> contained this:
> 
>   clang/lib/Driver/ToolChains/Clang.cpp
>   @@ -2768,7 +2766,7 @@ static void RenderFloatingPointOptions(const
> ToolChain &TC, const Driver &D,
>           !AssociativeMath && !ReciprocalMath &&
>           SignedZeros && TrappingMath && RoundingFPMath &&
>           DenormalFPMath != llvm::DenormalMode::getIEEE() &&
>   +        FPContract.empty())
>   -        (FPContract.equals("off") || FPContract.empty()))
> 
> But sometime in the land-revert-land-revert cycle the line above that changed,
> causing the merge to miss this change in the most recent revert. I see that
> @MaskRay has since re-landed this change set, but it's going to cause problems
> for PowerPC. If someone needs to revert this yet again, I think it can be safely
> done by recovering the change above.
> 
> Apologies for the mess!
> 
> 
> Repository:
>   rG LLVM Github Monorepo
> 
> CHANGES SINCE LAST ACTION
>   https://reviews.llvm.org/D74436/new/
> 
> https://reviews.llvm.org/D74436
> 
>