AArch64: remove post-encoder method from FCMP (immediate) instructions.

The work done by the post-encoder (setting architecturally unused bits to 0 as
required) can be done by the existing operand that covers the "#0.0". This
removes at least one use of the discouraged PostEncoderMethod uses.

llvm-svn: 176261
diff --git a/llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp b/llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
index eba7666..12c1b8f 100644
--- a/llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
+++ b/llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp
@@ -106,6 +106,11 @@
                                                uint64_t Address,
                                                const void *Decoder);
 
+static DecodeStatus DecodeFPZeroOperand(llvm::MCInst &Inst,
+                                        unsigned RmBits,
+                                        uint64_t Address,
+                                        const void *Decoder);
+
 template<int RegWidth>
 static DecodeStatus DecodeMoveWideImmOperand(llvm::MCInst &Inst,
                                              unsigned FullImm,
@@ -381,6 +386,17 @@
   return MCDisassembler::Success;
 }
 
+static DecodeStatus DecodeFPZeroOperand(llvm::MCInst &Inst,
+                                        unsigned RmBits,
+                                        uint64_t Address,
+                                        const void *Decoder) {
+  // Any bits are valid in the instruction (they're architecturally ignored),
+  // but a code generator should insert 0.
+  Inst.addOperand(MCOperand::CreateImm(0));
+  return MCDisassembler::Success;
+}
+
+
 
 template<int RegWidth>
 static DecodeStatus DecodeMoveWideImmOperand(llvm::MCInst &Inst,