PPC NCG: Lower MO_*_Fabs as PowerPC fabs instruction

Authored by trommler on May 1 2017, 10:17 AM.

Description

PPC NCG: Lower MO_*_Fabs as PowerPC fabs instruction

In Phab:D3265 we introduced MO_F32_Fabs and MO_F64_Fabs.
This patch improves code generation by generating PowerPC fabs
instructions.

Test Plan: run numeric/should_run/numrun015 or validate

Reviewers: austin, bgamari, hvr, simonmar, erikd

Reviewed By: erikd

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3512

(cherry picked from commit 068af0162a47b1fd7809d056ccc2d80e480d53f5)