Internalize strings in-place

src/ia32/code-stubs-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_IA32
 
 #include "src/code-stubs.h"
 #include "src/api-arguments.h"
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
@@ skipping 586 matching lines @@
   // (5) One byte sequential.  Load regexp code for one byte.
   // (E) Carry on.
   /// [...]
 
   // Deferred code at the end of the stub:
   // (6) Long external string?  If not, go to (10).
   // (7) External string.  Make it, offset-wise, look like a sequential string.
   // (8) Is the external string one byte?  If yes, go to (5).
   // (9) Two byte sequential.  Load regexp code for two byte. Go to (E).
   // (10) Short external string or not a string?  If yes, bail out to runtime.
-  // (11) Sliced string.  Replace subject with parent. Go to (1).
+  // (11) Sliced or thin string.  Replace subject with parent. Go to (1).
 
   Label seq_one_byte_string /* 5 */, seq_two_byte_string /* 9 */,
       external_string /* 7 */, check_underlying /* 1 */,
       not_seq_nor_cons /* 6 */, check_code /* E */, not_long_external /* 10 */;
 
   __ bind(&check_underlying);
   // (1) Sequential two byte?  If yes, go to (9).
   __ mov(ebx, FieldOperand(eax, HeapObject::kMapOffset));
   __ movzx_b(ebx, FieldOperand(ebx, Map::kInstanceTypeOffset));
 
   __ and_(ebx, kIsNotStringMask |
                kStringRepresentationMask |
                kStringEncodingMask |
                kShortExternalStringMask);
   STATIC_ASSERT((kStringTag | kSeqStringTag | kTwoByteStringTag) == 0);
   __ j(zero, &seq_two_byte_string);  // Go to (9).
 
   // (2) Sequential one byte?  If yes, go to (5).
   // Any other sequential string must be one byte.
   __ and_(ebx, Immediate(kIsNotStringMask |
                          kStringRepresentationMask |
                          kShortExternalStringMask));
   __ j(zero, &seq_one_byte_string, Label::kNear);  // Go to (5).
 
   // (3) Sequential or cons?  If not, go to (6).
   // We check whether the subject string is a cons, since sequential strings
   // have already been covered.
   STATIC_ASSERT(kConsStringTag < kExternalStringTag);
   STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);

[Igor Sheludko, 2016/12/20 23:46:58]

Maybe
  STATIC_ASSERT(kThinStringTag > kExternalStringTag);
here and in other ports?

[Jakob Kummerow, 2017/01/04 12:45:06]

Done.

   STATIC_ASSERT(kIsNotStringMask > kExternalStringTag);
   STATIC_ASSERT(kShortExternalStringTag > kExternalStringTag);
   __ cmp(ebx, Immediate(kExternalStringTag));
   __ j(greater_equal, &not_seq_nor_cons);  // Go to (6).
 
   // (4) Cons string.  Check that it's flat.
   // Replace subject with first string and reload instance type.
   __ cmp(FieldOperand(eax, ConsString::kSecondOffset), factory->empty_string());
   __ j(not_equal, &runtime);
   __ mov(eax, FieldOperand(eax, ConsString::kFirstOffset));
@@ skipping 258 matching lines @@
   __ Move(ecx, Immediate(0));  // Type is two byte.
   __ jmp(&check_code);  // Go to (E).
 
   // (10) Not a string or a short external string?  If yes, bail out to runtime.
   __ bind(&not_long_external);
   // Catch non-string subject or short external string.
   STATIC_ASSERT(kNotStringTag != 0 && kShortExternalStringTag !=0);
   __ test(ebx, Immediate(kIsNotStringMask | kShortExternalStringTag));
   __ j(not_zero, &runtime);
 
-  // (11) Sliced string.  Replace subject with parent.  Go to (1).
+  // (11) Sliced or thin string.  Replace subject with parent.  Go to (1).
+  Label thin_string;
+  __ cmp(ebx, Immediate(kThinStringTag));
+  __ j(equal, &thin_string, Label::kNear);
   // Load offset into edi and replace subject string with parent.
   __ mov(edi, FieldOperand(eax, SlicedString::kOffsetOffset));
   __ mov(eax, FieldOperand(eax, SlicedString::kParentOffset));
   __ jmp(&check_underlying);  // Go to (1).
+
+  __ bind(&thin_string);
+  __ mov(eax, FieldOperand(eax, ThinString::kActualOffset));
+  __ jmp(&check_underlying);  // Go to (1).
 #endif  // V8_INTERPRETED_REGEXP
 }
 
 
 static int NegativeComparisonResult(Condition cc) {
   DCHECK(cc != equal);
   DCHECK((cc == less) || (cc == less_equal)
       || (cc == greater) || (cc == greater_equal));
   return (cc == greater || cc == greater_equal) ? LESS : GREATER;
 }
@@ skipping 3488 matching lines @@
                            kStackUnwindSpace, nullptr, return_value_operand,
                            NULL);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_IA32