Add support for passing and returning vectors in accordance with the x86 calling convention.

src/IceOperand.h

Index: src/IceOperand.h
diff --git a/src/IceOperand.h b/src/IceOperand.h
index 018445a60bbc197b12091e4a59edc82fb1f8ff07..9beeed6d78486863af6a91d5e5ad447034e25750 100644
--- a/src/IceOperand.h
+++ b/src/IceOperand.h
@@ -341,6 +341,15 @@ public:
   bool getIsArg() const { return IsArgument; }
   void setIsArg(Cfg *Func);
 
+  enum ArgLocInfo {
+    NoArgLoc,
+    RegisterArgLoc,
+    StackArgLoc
+  };
+
+  ArgLocInfo getArgLoc() const { return ArgLoc; }
+  void setArgLoc(ArgLocInfo Loc) { ArgLoc = Loc; }
+
   int32_t getStackOffset() const { return StackOffset; }
   void setStackOffset(int32_t Offset) { StackOffset = Offset; }
 
@@ -356,6 +365,11 @@ public:
   int32_t getRegNumTmp() const { return RegNumTmp; }
   void setRegNumTmp(int32_t NewRegNum) { RegNumTmp = NewRegNum; }
 
+  Variable *getHomeRegister() const { return HomeRegister; }
+  void setHomeRegister(Variable *NewHomeRegister) {
+    HomeRegister = NewHomeRegister;
+  }
+
   RegWeight getWeight() const { return Weight; }
   void setWeight(uint32_t NewWeight) { Weight = NewWeight; }
   void setWeightInfinite() { Weight = RegWeight::Inf; }
@@ -410,7 +424,8 @@ private:
       : Operand(kVariable, Ty), Number(Index), Name(Name), DefInst(NULL),
         DefNode(Node), IsArgument(false), StackOffset(0), RegNum(NoRegister),
         RegNumTmp(NoRegister), Weight(1), RegisterPreference(NULL),
-        AllowRegisterOverlap(false), LoVar(NULL), HiVar(NULL) {
+        AllowRegisterOverlap(false), LoVar(NULL), HiVar(NULL),
+        ArgLoc(NoArgLoc), HomeRegister(NULL) {
     Vars = VarsReal;
     Vars[0] = this;
     NumVars = 1;
@@ -462,6 +477,11 @@ private:
   // wasteful for a 64-bit target.
   Variable *LoVar;
   Variable *HiVar;
+  // ArgLoc records the assignment of the argument (stack or register)
+  // if this value is an argument.
+  ArgLocInfo ArgLoc;
+  // HomeRegister is the home register.
+  Variable *HomeRegister;
   // VarsReal (and Operand::Vars) are set up such that Vars[0] ==
   // this.
   Variable *VarsReal[1];