ARM64: Sign extension on MemOperand for keyed ops

SXTW extend mode is usually cheaper on loads and stores than arithmetic,
so move it to the memory accesses where possible for Keyed loads and
stores.

BUG=
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/268483002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21172 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm64/assembler-arm64-inl.h

@@ -411,6 +411,12 @@ Operand Operand::UntagSmiAndScale(Register smi, int scale) {
 }
 
 
+MemOperand::MemOperand()
+  : base_(NoReg), regoffset_(NoReg), offset_(0), addrmode_(Offset),
+    shift_(NO_SHIFT), extend_(NO_EXTEND), shift_amount_(0) {
+}
+
+
 MemOperand::MemOperand(Register base, ptrdiff_t offset, AddrMode addrmode)
   : base_(base), regoffset_(NoReg), offset_(offset), addrmode_(addrmode),
     shift_(NO_SHIFT), extend_(NO_EXTEND), shift_amount_(0) {

src/arm64/assembler-arm64.h

@@ -669,6 +669,7 @@ class Operand {
 // MemOperand represents a memory operand in a load or store instruction.
 class MemOperand {
  public:
+  inline explicit MemOperand();
   inline explicit MemOperand(Register base,
                              ptrdiff_t offset = 0,
                              AddrMode addrmode = Offset);

src/arm64/lithium-arm64.cc

@@ -1666,10 +1666,9 @@ LInstruction* LChunkBuilder::DoLoadKeyed(HLoadKeyed* instr) {
   ASSERT(instr->key()->representation().IsSmiOrInteger32());
   ElementsKind elements_kind = instr->elements_kind();
   LOperand* elements = UseRegister(instr->elements());
+  LOperand* key = UseRegisterOrConstant(instr->key());
 
   if (!instr->is_typed_elements()) {
-    LOperand* key = UseRegisterOrConstantAtStart(instr->key());
-
     if (instr->representation().IsDouble()) {
       LOperand* temp = (!instr->key()->IsConstant() ||
                         instr->RequiresHoleCheck())
@@ -1697,7 +1696,6 @@ LInstruction* LChunkBuilder::DoLoadKeyed(HLoadKeyed* instr) {
            (instr->representation().IsDouble() &&
             IsDoubleOrFloatElementsKind(instr->elements_kind())));
 
-    LOperand* key = UseRegisterOrConstant(instr->key());
     LOperand* temp = instr->key()->IsConstant() ? NULL : TempRegister();
     LInstruction* result = DefineAsRegister(
         new(zone()) LLoadKeyedExternal(elements, key, temp));
@@ -2301,6 +2299,7 @@ LInstruction* LChunkBuilder::DoStoreGlobalCell(HStoreGlobalCell* instr) {
 
 
 LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
+  LOperand* key = UseRegisterOrConstant(instr->key());
   LOperand* temp = NULL;
   LOperand* elements = NULL;
   LOperand* val = NULL;
@@ -2327,19 +2326,16 @@ LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
             instr->elements()->representation().IsTagged()) ||
            (instr->is_external() &&
             instr->elements()->representation().IsExternal()));
-    LOperand* key = UseRegisterOrConstant(instr->key());
     return new(zone()) LStoreKeyedExternal(elements, key, val, temp);
 
   } else if (instr->value()->representation().IsDouble()) {
     ASSERT(instr->elements()->representation().IsTagged());
-    LOperand* key = UseRegisterOrConstantAtStart(instr->key());
     return new(zone()) LStoreKeyedFixedDouble(elements, key, val, temp);
 
   } else {
     ASSERT(instr->elements()->representation().IsTagged());
     ASSERT(instr->value()->representation().IsSmiOrTagged() ||
            instr->value()->representation().IsInteger32());
-    LOperand* key = UseRegisterOrConstantAtStart(instr->key());
     return new(zone()) LStoreKeyedFixed(elements, key, val, temp);
   }
 }

src/arm64/lithium-codegen-arm64.h

@@ -256,11 +256,13 @@ class LCodeGen: public LCodeGenBase {
                                               int constant_key,
                                               ElementsKind elements_kind,
                                               int additional_index);
-  void CalcKeyedArrayBaseRegister(Register base,
-                                  Register elements,
-                                  Register key,
-                                  bool key_is_tagged,
-                                  ElementsKind elements_kind);
+  MemOperand PrepareKeyedArrayOperand(Register base,
+                                      Register elements,
+                                      Register key,
+                                      bool key_is_tagged,
+                                      ElementsKind elements_kind,
+                                      Representation representation,
+                                      int additional_index);
 
   void RegisterEnvironmentForDeoptimization(LEnvironment* environment,
                                             Safepoint::DeoptMode mode);