Make FP zero to be legal FP immediate via LOAD ZERO

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76034 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/SystemZ/SystemZISelLowering.cpp b/lib/Target/SystemZ/SystemZISelLowering.cpp
index 01ecf4f..4144f97 100644
--- a/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -51,6 +51,11 @@
   if (!UseSoftFloat) {
     addRegisterClass(MVT::f32, SystemZ::FP32RegisterClass);
     addRegisterClass(MVT::f64, SystemZ::FP64RegisterClass);
+
+    addLegalFPImmediate(APFloat(+0.0));  // lzer
+    addLegalFPImmediate(APFloat(+0.0f)); // lzdr
+    addLegalFPImmediate(APFloat(-0.0));  // lzer + lner
+    addLegalFPImmediate(APFloat(-0.0f)); // lzdr + lndr
   }
 
   // Compute derived properties from the register classes