MIPS: Implement Neg_d and Neg_s instruction macros.

src/mips/assembler-mips.cc

Index: src/mips/assembler-mips.cc
diff --git a/src/mips/assembler-mips.cc b/src/mips/assembler-mips.cc
index ab57e875489f3f3e3bbecc99eda51c4f35f14bff..20a8a11fbb1d92f55c1e2664a490ab59a59c4638 100644
--- a/src/mips/assembler-mips.cc
+++ b/src/mips/assembler-mips.cc
@@ -2492,11 +2492,13 @@ void Assembler::mov_s(FPURegister fd, FPURegister fs) {
 
 
 void Assembler::neg_s(FPURegister fd, FPURegister fs) {
+  DCHECK(!IsMipsArchVariant(kMips32r6));
   GenInstrRegister(COP1, S, f0, fs, fd, NEG_S);
 }
 
 
 void Assembler::neg_d(FPURegister fd, FPURegister fs) {
+  DCHECK(!IsMipsArchVariant(kMips32r6));
   GenInstrRegister(COP1, D, f0, fs, fd, NEG_D);
 }