[Sparc] Use the IntPair reg class for r constraints with value type f64

Summary: This is how it appears to be handled in GCC and it prevents a
"Unknown mismatch" error in the SelectionDAGBuilder.

Reviewers: venkatra, jyknight, jrtc27

Reviewed By: jyknight, jrtc27

Subscribers: eraman, fedor.sergeev, jrtc27, llvm-commits

Differential Revision: https://reviews.llvm.org/D49218

llvm-svn: 337370
diff --git a/llvm/lib/Target/Sparc/SparcISelLowering.cpp b/llvm/lib/Target/Sparc/SparcISelLowering.cpp
index b04c6b1..178bb53 100644
--- a/llvm/lib/Target/Sparc/SparcISelLowering.cpp
+++ b/llvm/lib/Target/Sparc/SparcISelLowering.cpp
@@ -3489,7 +3489,7 @@
   if (Constraint.size() == 1) {
     switch (Constraint[0]) {
     case 'r':
-      if (VT == MVT::v2i32)
+      if (VT == MVT::v2i32 || VT == MVT::f64)
         return std::make_pair(0U, &SP::IntPairRegClass);
       else
         return std::make_pair(0U, &SP::IntRegsRegClass);