Subzero: Remove unneeded ScratchRegs.

src/IceTargetLoweringX8664Traits.h

Index: src/IceTargetLoweringX8664Traits.h
diff --git a/src/IceTargetLoweringX8664Traits.h b/src/IceTargetLoweringX8664Traits.h
index b206817eea4a413744963eade01f362ba788425d..39c5b95ba4cdf8c2361e9b853610348552184563 100644
--- a/src/IceTargetLoweringX8664Traits.h
+++ b/src/IceTargetLoweringX8664Traits.h
@@ -492,8 +492,7 @@ public:
   static void initRegisterSet(
       const ::Ice::ClFlags &Flags,
       std::array<llvm::SmallBitVector, RCX86_NUM> *TypeToRegisterSet,
-      std::array<llvm::SmallBitVector, RegisterSet::Reg_NUM> *RegisterAliases,
-      llvm::SmallBitVector *ScratchRegs) {
+      std::array<llvm::SmallBitVector, RegisterSet::Reg_NUM> *RegisterAliases) {
     llvm::SmallBitVector IntegerRegistersI64(RegisterSet::Reg_NUM);
     llvm::SmallBitVector IntegerRegistersI32(RegisterSet::Reg_NUM);
     llvm::SmallBitVector IntegerRegistersI16(RegisterSet::Reg_NUM);
@@ -506,7 +505,6 @@ public:
     llvm::SmallBitVector Trunc8RcvrRegisters(RegisterSet::Reg_NUM);
     llvm::SmallBitVector AhRcvrRegisters(RegisterSet::Reg_NUM);
     llvm::SmallBitVector InvalidRegisters(RegisterSet::Reg_NUM);
-    ScratchRegs->resize(RegisterSet::Reg_NUM);
 
     static constexpr struct {
       uint16_t Val;
@@ -521,7 +519,6 @@ public:
       unsigned Is16To8 : 1;
       unsigned IsTrunc8Rcvr : 1;
       unsigned IsAhRcvr : 1;
-      unsigned Scratch : 1;
 #define NUM_ALIASES_BITS 2
       SizeT NumAliases : (NUM_ALIASES_BITS + 1);
       uint16_t Aliases[1 << NUM_ALIASES_BITS];
@@ -532,8 +529,7 @@ public:
           is16To8, isTrunc8Rcvr, isAhRcvr, aliases)                            \
   {                                                                            \
     RegisterSet::val, sboxres, is64, is32, is16, is8, isXmm, is64To8, is32To8, \
-        is16To8, isTrunc8Rcvr, isAhRcvr, scratch, (SizeOf aliases).size(),     \
-        aliases,                                                               \
+        is16To8, isTrunc8Rcvr, isAhRcvr, (SizeOf aliases).size(), aliases,     \
   }                                                                            \
   ,
         REGX8664_TABLE
@@ -570,7 +566,6 @@ public:
       (Trunc16To8Registers)[Entry.Val] = Entry.Is16To8;
       (Trunc8RcvrRegisters)[Entry.Val] = Entry.IsTrunc8Rcvr;
       (AhRcvrRegisters)[Entry.Val] = Entry.IsAhRcvr;
-      (*ScratchRegs)[Entry.Val] = Entry.Scratch;
     }
 
     (*TypeToRegisterSet)[RC_void] = InvalidRegisters;