Microoptimization to regexps.

Review URL: https://chromiumcodereview.appspot.com/10917260

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12511 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/code-stubs-arm.cc

@@ -5232,12 +5232,12 @@ void RegExpConstructResultStub::Generate(MacroAssembler* masm) {
   // Set FixedArray length.
   __ mov(r6, Operand(r5, LSL, kSmiTagSize));
   __ str(r6, FieldMemOperand(r3, FixedArray::kLengthOffset));
-  // Fill contents of fixed-array with the-hole.
-  __ mov(r2, Operand(factory->the_hole_value()));
+  // Fill contents of fixed-array with undefined.
+  __ LoadRoot(r2, Heap::kUndefinedValueRootIndex);
   __ add(r3, r3, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
-  // Fill fixed array elements with hole.
+  // Fill fixed array elements with undefined.
   // r0: JSArray, tagged.
-  // r2: the hole.
+  // r2: undefined.
   // r3: Start of elements in FixedArray.
   // r5: Number of elements to fill.
   Label loop;

src/ia32/code-stubs-ia32.cc

@@ -4170,15 +4170,15 @@ void RegExpConstructResultStub::Generate(MacroAssembler* masm) {
          Immediate(factory->fixed_array_map()));
   // Set length.
   __ mov(FieldOperand(ebx, FixedArray::kLengthOffset), ecx);
-  // Fill contents of fixed-array with the-hole.
+  // Fill contents of fixed-array with undefined.
   __ SmiUntag(ecx);
-  __ mov(edx, Immediate(factory->the_hole_value()));
+  __ mov(edx, Immediate(factory->undefined_value()));
   __ lea(ebx, FieldOperand(ebx, FixedArray::kHeaderSize));
-  // Fill fixed array elements with hole.
+  // Fill fixed array elements with undefined.
   // eax: JSArray.
   // ecx: Number of elements to fill.
   // ebx: Start of elements in FixedArray.
-  // edx: the hole.
+  // edx: undefined.
   Label loop;
   __ test(ecx, ecx);
   __ bind(&loop);

src/mips/code-stubs-mips.cc

@@ -5405,12 +5405,12 @@ void RegExpConstructResultStub::Generate(MacroAssembler* masm) {
   // Set FixedArray length.
   __ sll(t2, t1, kSmiTagSize);
   __ sw(t2, FieldMemOperand(a3, FixedArray::kLengthOffset));
-  // Fill contents of fixed-array with the-hole.
-  __ li(a2, Operand(masm->isolate()->factory()->the_hole_value()));
+  // Fill contents of fixed-array with undefined.
+  __ LoadRoot(a2, Heap::kUndefinedValueRootIndex);
   __ Addu(a3, a3, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
-  // Fill fixed array elements with hole.
+  // Fill fixed array elements with undefined.
   // v0: JSArray, tagged.
-  // a2: the hole.
+  // a2: undefined.
   // a3: Start of elements in FixedArray.
   // t1: Number of elements to fill.
   Label loop;

src/regexp.js

@@ -140,18 +140,15 @@ function BuildResultFromMatchInfo(lastMatchInfo, s) {
   var j = REGEXP_FIRST_CAPTURE + 2;
   for (var i = 1; i < numResults; i++) {
     start = lastMatchInfo[j++];
-    end = lastMatchInfo[j++];
-    if (end != -1) {
+    if (start != -1) {
+      end = lastMatchInfo[j];
       if (start + 1 == end) {
         result[i] = %_StringCharAt(s, start);
       } else {
         result[i] = %_SubString(s, start, end);
       }
-    } else {
-      // Make sure the element is present. Avoid reading the undefined
-      // property from the global object since this may change.
-      result[i] = void 0;
     }
+    j++;
   }
   return result;
 }

src/x64/code-stubs-x64.cc

@@ -3235,14 +3235,14 @@ void RegExpConstructResultStub::Generate(MacroAssembler* masm) {
   // Set length.
   __ Integer32ToSmi(rdx, rbx);
   __ movq(FieldOperand(rcx, FixedArray::kLengthOffset), rdx);
-  // Fill contents of fixed-array with the-hole.
-  __ LoadRoot(rdx, Heap::kTheHoleValueRootIndex);
+  // Fill contents of fixed-array with undefined.
+  __ LoadRoot(rdx, Heap::kUndefinedValueRootIndex);
   __ lea(rcx, FieldOperand(rcx, FixedArray::kHeaderSize));
-  // Fill fixed array elements with hole.
+  // Fill fixed array elements with undefined.
   // rax: JSArray.
   // rbx: Number of elements in array that remains to be filled, as int32.
   // rcx: Start of elements in FixedArray.
-  // rdx: the hole.
+  // rdx: undefined.
   Label loop;
   __ testl(rbx, rbx);
   __ bind(&loop);