ARM: Improve SeqStringSetChar implementation.

TEST=/test/mjsunit/lithium/SeqStringSetChar.js
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/23890007

Patch from Rodolph Perfetta <rodolph.perfetta@gmail.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16707 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-arm.cc

@@ -1883,11 +1883,9 @@ LInstruction* LChunkBuilder::DoDateField(HDateField* instr) {
 
 LInstruction* LChunkBuilder::DoSeqStringSetChar(HSeqStringSetChar* instr) {
   LOperand* string = UseRegister(instr->string());
-  LOperand* index = UseRegister(instr->index());
-  LOperand* value = UseTempRegister(instr->value());
-  LSeqStringSetChar* result =
-      new(zone()) LSeqStringSetChar(instr->encoding(), string, index, value);
-  return DefineAsRegister(result);
+  LOperand* index = UseRegisterOrConstant(instr->index());
+  LOperand* value = UseRegister(instr->value());
+  return new(zone()) LSeqStringSetChar(instr->encoding(), string, index, value);
 }
 
 

src/arm/lithium-codegen-arm.cc

@@ -1975,32 +1975,42 @@ void LCodeGen::DoDateField(LDateField* instr) {
 
 void LCodeGen::DoSeqStringSetChar(LSeqStringSetChar* instr) {
   Register string = ToRegister(instr->string());
-  Register index = ToRegister(instr->index());
+  LOperand* index_op = instr->index();
   Register value = ToRegister(instr->value());
+  Register scratch = scratch0();
   String::Encoding encoding = instr->encoding();
 
   if (FLAG_debug_code) {
-    __ ldr(ip, FieldMemOperand(string, HeapObject::kMapOffset));
-    __ ldrb(ip, FieldMemOperand(ip, Map::kInstanceTypeOffset));
+    __ ldr(scratch, FieldMemOperand(string, HeapObject::kMapOffset));
+    __ ldrb(scratch, FieldMemOperand(scratch, Map::kInstanceTypeOffset));
 
-    __ and_(ip, ip, Operand(kStringRepresentationMask | kStringEncodingMask));
+    __ and_(scratch, scratch,
+            Operand(kStringRepresentationMask | kStringEncodingMask));
     static const uint32_t one_byte_seq_type = kSeqStringTag | kOneByteStringTag;
     static const uint32_t two_byte_seq_type = kSeqStringTag | kTwoByteStringTag;
-    __ cmp(ip, Operand(encoding == String::ONE_BYTE_ENCODING
-                           ? one_byte_seq_type : two_byte_seq_type));
+    __ cmp(scratch, Operand(encoding == String::ONE_BYTE_ENCODING
+                            ? one_byte_seq_type : two_byte_seq_type));
     __ Check(eq, kUnexpectedStringType);
   }
 
-  __ add(ip,
-         string,
-         Operand(SeqString::kHeaderSize - kHeapObjectTag));
-  if (encoding == String::ONE_BYTE_ENCODING) {
-    __ strb(value, MemOperand(ip, index));
+  if (index_op->IsConstantOperand()) {
+    int constant_index = ToInteger32(LConstantOperand::cast(index_op));
+    if (encoding == String::ONE_BYTE_ENCODING) {
+      __ strb(value,
+              FieldMemOperand(string, SeqString::kHeaderSize + constant_index));
+    } else {
+      __ strh(value,
+          FieldMemOperand(string, SeqString::kHeaderSize + constant_index * 2));
+    }
   } else {
-    // MemOperand with ip as the base register is not allowed for strh, so
-    // we do the address calculation explicitly.
-    __ add(ip, ip, Operand(index, LSL, 1));
-    __ strh(value, MemOperand(ip));
+    Register index = ToRegister(index_op);
+    if (encoding == String::ONE_BYTE_ENCODING) {
+      __ add(scratch, string, Operand(index));
+      __ strb(value, FieldMemOperand(scratch, SeqString::kHeaderSize));
+    } else {
+      __ add(scratch, string, Operand(index, LSL, 1));
+      __ strh(value, FieldMemOperand(scratch, SeqString::kHeaderSize));
+    }
   }
 }
 

test/mjsunit/lithium/SeqStringSetChar.js

+// 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax
+
+function MyStringFromCharCode(code, i) {
+  var one_byte = %NewString(3, true);
+  %_OneByteSeqStringSetChar(one_byte, 0, code);
+  %_OneByteSeqStringSetChar(one_byte, 1, code);
+  %_OneByteSeqStringSetChar(one_byte, i, code);
+  var two_byte = %NewString(3, false);
+  %_TwoByteSeqStringSetChar(two_byte, 0, code);
+  %_TwoByteSeqStringSetChar(two_byte, 1, code);
+  %_TwoByteSeqStringSetChar(two_byte, i, code);
+  return one_byte + two_byte;
+}
+
+MyStringFromCharCode(65, 2);
+var r1 = MyStringFromCharCode(65, 2);
+%OptimizeFunctionOnNextCall(MyStringFromCharCode);
+var r2 = MyStringFromCharCode(65, 2);
+assertEquals(r1, r2);