implement the null function for the Mips32 subzero compiler

src/IceInstMIPS32.h

Index: src/IceInstMIPS32.h
diff --git a/src/IceInstMIPS32.h b/src/IceInstMIPS32.h
index 17c25833b9a28eb033eb9df416769bef1ad70c9d..52cae719388fe163cc62a40a34bf4ee3625f39a9 100644
--- a/src/IceInstMIPS32.h
+++ b/src/IceInstMIPS32.h
@@ -18,11 +18,63 @@
 #define SUBZERO_SRC_ICEINSTMIPS32_H
 
 #include "IceDefs.h"
+#include "IceInst.h"
+#include "IceInstMIPS32.def"
+#include "IceOperand.h"
 
 namespace Ice {
 
 class TargetMIPS32;
-// Fill this in.
+// Base class for Mips instructions.

[jvoung (off chromium), 2015/07/07 18:02:35]

Newline between "class TargetMIPS32" and the start of the classes for insts.

Also, we started to doxygenize some comments. Could you convert the "//" which
you think should appear in generated documentation into "///"?

[reed.kotler, 2015/07/07 21:54:54]

Done.

[jvoung (off chromium), 2015/07/08 00:39:11]

Doesn't appear to be inserted?

[reed.kotler, 2015/07/08 02:05:16]

Done.

+class InstMIPS32 : public InstTarget {
+  InstMIPS32() = delete;
+  InstMIPS32(const InstMIPS32 &) = delete;
+  InstMIPS32 &operator=(const InstMIPS32 &) = delete;
+
+public:
+  enum InstKindMIPS32 { k__Start = Inst::Target, Ret };
+
+  static const char *getWidthString(Type Ty);
+
+  void dump(const Cfg *Func) const override;
+
+protected:
+  InstMIPS32(Cfg *Func, InstKindMIPS32 Kind, SizeT Maxsrcs, Variable *Dest)
+      : InstTarget(Func, static_cast<InstKind>(Kind), Maxsrcs, Dest) {}
+  ~InstMIPS32() override {}
+  static bool isClassof(const Inst *Inst, InstKindMIPS32 MyKind) {
+    return Inst->getKind() == static_cast<InstKind>(MyKind);
+  }
+};
+
+// Ret pseudo-instruction.  This is actually a "jr" instruction with
+// an "ra" register operand, but epilogue lowering will search for a Ret
+// instead of a generic "jr". This instruction also takes a Source
+// operand (for non-void returning functions) for liveness analysis, though
+// a FakeUse before the ret would do just as well.
+// This needs was take from the ARM port and needs to be scrubbed in the future
+// (TODO Reed Kotler)

[jvoung (off chromium), 2015/07/07 18:02:35]

Please use a more consistent TODO marker:

"TODO(reed kotler)"

[reed.kotler, 2015/07/07 21:54:54]

Done.

[jvoung (off chromium), 2015/07/08 00:39:11]

"(TODO ...)" -> "TODO(...)"

[reed.kotler, 2015/07/08 02:05:16]

Done.

+//
+class InstMIPS32Ret : public InstMIPS32 {
+  InstMIPS32Ret() = delete;
+  InstMIPS32Ret(const InstMIPS32Ret &) = delete;
+  InstMIPS32Ret &operator=(const InstMIPS32Ret &) = delete;
+
+public:
+  static InstMIPS32Ret *create(Cfg *Func, Variable *LR,

[jvoung (off chromium), 2015/07/07 18:02:35]

LR -> RA in various places here and in the .cpp

[reed.kotler, 2015/07/07 21:54:54]

Done.

[jvoung (off chromium), 2015/07/08 00:39:11]

Doesn't appear to be done here (but done in other places)?

[reed.kotler, 2015/07/08 02:05:16]

Done.

+                               Variable *Source = nullptr) {
+    return new (Func->allocate<InstMIPS32Ret>())
+        InstMIPS32Ret(Func, LR, Source);
+  }
+  void emit(const Cfg *Func) const override;
+  void emitIAS(const Cfg *Func) const override;
+  void dump(const Cfg *Func) const override;
+  static bool classof(const Inst *Inst) { return isClassof(Inst, Ret); }
+
+private:
+  InstMIPS32Ret(Cfg *Func, Variable *LR, Variable *Source);
+  ~InstMIPS32Ret() override {}
+};
 
 } // end of namespace Ice