A64: Port LSeqStringSetChar optimizations from r16707 and r17521.

src/a64/lithium-codegen-a64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4553 matching lines @@
       BuildSeqStringOperand(string, temp, instr->index(), encoding);
   if (encoding == String::ONE_BYTE_ENCODING) {
     __ Ldrb(result, operand);
   } else {
     __ Ldrh(result, operand);
   }
 }
 
 
 void LCodeGen::DoSeqStringSetChar(LSeqStringSetChar* instr) {
-  // TODO(all): Port ARM optimizations from r16707.
-
   String::Encoding encoding = instr->encoding();
   Register string = ToRegister(instr->string());
-  Register index = ToRegister(instr->index());
   Register value = ToRegister(instr->value());
   Register temp = ToRegister(instr->temp());
 
   if (FLAG_debug_code) {
-    if (encoding == String::ONE_BYTE_ENCODING) {
-      __ EmitSeqStringSetCharCheck(
-          string, index, kSeqStringTag | kOneByteStringTag);
-    } else {
-      ASSERT(encoding == String::TWO_BYTE_ENCODING);
-      __ EmitSeqStringSetCharCheck(
-          string, index, kSeqStringTag | kTwoByteStringTag);
-    }
+    Register index = ToRegister(instr->index());
+    static const uint32_t one_byte_seq_type = kSeqStringTag | kOneByteStringTag;
+    static const uint32_t two_byte_seq_type = kSeqStringTag | kTwoByteStringTag;
+    int encoding_mask =
+        instr->hydrogen()->encoding() == String::ONE_BYTE_ENCODING
+        ? one_byte_seq_type : two_byte_seq_type;
+    __ EmitSeqStringSetCharCheck(string, index, temp, encoding_mask);
   }
-
-  __ Add(temp, string, SeqString::kHeaderSize - kHeapObjectTag);
+  MemOperand operand =
+      BuildSeqStringOperand(string, temp, instr->index(), encoding);
   if (encoding == String::ONE_BYTE_ENCODING) {
-    __ Strb(value, MemOperand(temp, index));
+    __ Strb(value, operand);
   } else {
-    __ Strh(value, MemOperand(temp, index, LSL, 1));
+    __ Strh(value, operand);
   }
 }
 
 
 void LCodeGen::DoSmiTag(LSmiTag* instr) {
   ASSERT(!instr->hydrogen_value()->CheckFlag(HValue::kCanOverflow));
   __ SmiTag(ToRegister(instr->result()), ToRegister(instr->value()));
 }
 
 
@@ skipping 1128 matching lines @@
   __ Bind(&out_of_object);
   __ Ldr(result, FieldMemOperand(object, JSObject::kPropertiesOffset));
   // Index is equal to negated out of object property index plus 1.
   __ Sub(result, result, Operand::UntagSmiAndScale(index, kPointerSizeLog2));
   __ Ldr(result, FieldMemOperand(result,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ Bind(&done);
 }
 
 } }  // namespace v8::internal