[PowerPC] Use the two-constant NR algorithm for refining estimates

The single-constant algorithm produces infinities on a lot of denormal values.
The precision of the two-constant algorithm is actually sufficient across the
range of denormals. We will switch to that algorithm for now to avoid the
infinities on denormals. In the future, we will re-evaluate the algorithm to
find the optimal one for PowerPC.

Differential revision: https://reviews.llvm.org/D60037

llvm-svn: 360144

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.h b/llvm/lib/Target/PowerPC/PPCSubtarget.h
index fd050880161..1e03726ba76 100644
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.h
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.h
@@ -98,6 +98,7 @@ protected:
   bool HasSPE;
   bool HasQPX;
   bool HasVSX;
+  bool NeedsTwoConstNR;
   bool HasP8Vector;
   bool HasP8Altivec;
   bool HasP8Crypto;
@@ -246,6 +247,7 @@ public:
   bool hasFPU() const { return HasFPU; }
   bool hasQPX() const { return HasQPX; }
   bool hasVSX() const { return HasVSX; }
+  bool needsTwoConstNR() const { return NeedsTwoConstNR; }
   bool hasP8Vector() const { return HasP8Vector; }
   bool hasP8Altivec() const { return HasP8Altivec; }
   bool hasP8Crypto() const { return HasP8Crypto; }