Subzero: Randomize register assignment.

src/IceTargetLowering.h

Index: src/IceTargetLowering.h
diff --git a/src/IceTargetLowering.h b/src/IceTargetLowering.h
index 39e08def9b2c1a684d2437773f4ff76312e9ae80..d39b8e2ce82e513da8d0cec9710be29fa0c9632c 100644
--- a/src/IceTargetLowering.h
+++ b/src/IceTargetLowering.h
@@ -156,6 +156,10 @@ public:
   virtual const llvm::SmallBitVector &getRegisterSetForType(Type Ty) const = 0;
   void regAlloc();
 
+  virtual void makeRandomRegisterPermutation(
+      llvm::SmallVectorImpl<int32_t> &Permutation,
+      const llvm::SmallBitVector &ExcludeRegisters) = 0;
+
   virtual void emitVariable(const Variable *Var, const Cfg *Func) const = 0;
 
   // Performs target-specific argument lowering.
@@ -169,9 +173,7 @@ public:
   virtual ~TargetLowering() {}
 
 protected:
-  TargetLowering(Cfg *Func)
-      : Func(Func), Ctx(Func->getContext()), HasComputedFrame(false),
-        StackAdjustment(0) {}
+  TargetLowering(Cfg *Func);
   virtual void lowerAlloca(const InstAlloca *Inst) = 0;
   virtual void lowerArithmetic(const InstArithmetic *Inst) = 0;
   virtual void lowerAssign(const InstAssign *Inst) = 0;
@@ -208,6 +210,7 @@ protected:
   // natural location, as arguments are pushed for a function call.
   int32_t StackAdjustment;
   LoweringContext Context;
+  const bool RandomizeRegisterAllocation;
 
 private:
   TargetLowering(const TargetLowering &) LLVM_DELETED_FUNCTION;