[GlobalISel|ARM] : Allow legalizing G_FSUB

Adding support for VSUB.
Reviewed by: @rovka
Differential Revision: https://reviews.llvm.org/D39261

llvm-svn: 316902
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index cd6684f..99f605a 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -91,6 +91,9 @@
   case TargetOpcode::G_FADD:
     assert((Size == 32 || Size == 64) && "Unsupported size");
     return Size == 64 ? RTLIB::ADD_F64 : RTLIB::ADD_F32;
+  case TargetOpcode::G_FSUB:
+    assert((Size == 32 || Size == 64) && "Unsupported size");
+    return Size == 64 ? RTLIB::SUB_F64 : RTLIB::SUB_F32;
   case TargetOpcode::G_FREM:
     return Size == 64 ? RTLIB::REM_F64 : RTLIB::REM_F32;
   case TargetOpcode::G_FPOW:
@@ -146,6 +149,7 @@
     break;
   }
   case TargetOpcode::G_FADD:
+  case TargetOpcode::G_FSUB:
   case TargetOpcode::G_FPOW:
   case TargetOpcode::G_FREM: {
     Type *HLTy = Size == 64 ? Type::getDoubleTy(Ctx) : Type::getFloatTy(Ctx);