Intrinsify writing to Uint8 and Int8 arrays on IA32.

runtime/vm/intrinsifier_ia32.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // The intrinsic code below is executed before a method has built its frame.
 // The return address is on the stack and the arguments below it.
 // Registers EDX (arguments descriptor) and ECX (function) must be preserved.
 // Each intrinsification method returns true if the corresponding
 // Dart method was intrinsified.
 
@@ skipping 502 matching lines @@
                               EBX,
                               TIMES_1,
                               Int8Array::data_offset()));
   __ SmiTag(EAX);
   __ ret();
   __ Bind(&fall_through);
   return false;
 }
 
 
+bool Intrinsifier::Int8Array_setIndexed(Assembler* assembler) {
+  Label fall_through;
+  // Verify that the array index is valid.
+  TestByteArraySetIndex(assembler, &fall_through);

[srdjan, 2012/10/08 21:45:53]

Please add comments about register content.

+  __ SmiUntag(EBX);
+  // Move EBX into EDI.
+  __ movl(EDI, EBX);
+  // Move the value into EBX.
+  __ movl(EBX, Address(ESP, + 1 * kWordSize));  // Value.
+  // If EBX is not an Smi, jump to fall through.
+  __ testl(EBX, Immediate(kSmiTagMask));
+  __ j(NOT_ZERO, &fall_through, Assembler::kNearJump);
+  __ SmiUntag(EBX);
+  // If EBX is too large an Int8, jump to fall through.
+  __ cmpl(EBX, Immediate(0xFF));

[cshapiro, 2012/10/08 21:40:41]

We need to add 128 to EBX for this compare to be semantically correct.

It would be great to add a test for this condition, trying values on either side
of the range to ensure the boundary conditions are correctly accommodated.

+  __ j(GREATER, &fall_through, Assembler::kNearJump);
+  // Store EBX into array EAX[EDI] = EBX.
+  __ movb(FieldAddress(EAX, EDI, TIMES_1, Int8Array::data_offset()), BL);
+  __ ret();
+  __ Bind(&fall_through);
+  return false;
+}
+
+
 bool Intrinsifier::Uint8Array_getIndexed(Assembler* assembler) {
   Label fall_through;
   TestByteArrayIndex(assembler, &fall_through);
   __ SmiUntag(EBX);
   __ movzxb(EAX, FieldAddress(EAX,
                               EBX,
                               TIMES_1,
                               Uint8Array::data_offset()));
   __ SmiTag(EAX);
   __ ret();
   __ Bind(&fall_through);
   return false;
 }
 
 
+bool Intrinsifier::Uint8Array_setIndexed(Assembler* assembler) {
+  Label fall_through;
+  // Verify that the array index is valid.
+  TestByteArraySetIndex(assembler, &fall_through);

[srdjan, 2012/10/08 21:45:53]

ditto

+  __ SmiUntag(EBX);
+  // Move EBX into EDI.
+  __ movl(EDI, EBX);
+  // Move the value into EBX.
+  __ movl(EBX, Address(ESP, + 1 * kWordSize));  // Value.
+  // If EBX is not an Smi, jump to fall through.
+  __ testl(EBX, Immediate(kSmiTagMask));
+  __ j(NOT_ZERO, &fall_through, Assembler::kNearJump);
+  __ SmiUntag(EBX);
+  // If EBX is too large an Uint8, jump to fall through.
+  __ cmpl(EBX, Immediate(0xFF));
+  __ j(GREATER, &fall_through, Assembler::kNearJump);
+  // Store EBX into array EAX[EDI] = EBX.
+  __ movb(FieldAddress(EAX, EDI, TIMES_1, Uint8Array::data_offset()), BL);
+  __ ret();
+  __ Bind(&fall_through);
+  return false;
+}
+
+
 bool Intrinsifier::Int16Array_getIndexed(Assembler* assembler) {
   Label fall_through;
   TestByteArrayIndex(assembler, &fall_through);
   __ movsxw(EAX, FieldAddress(EAX,
                               EBX,
                               TIMES_1,
                               Int16Array::data_offset()));
   __ SmiTag(EAX);
   __ ret();
   __ Bind(&fall_through);
@@ skipping 950 matching lines @@
   __ Bind(&is_true);
   __ LoadObject(EAX, bool_true);
   __ ret();
   return true;
 }
 
 #undef __
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32