[regexp] do not assume short external strings have a minimum size.

src/x64/code-stubs-x64.cc

 // Copyright 2013 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_X64
 
 #include "src/code-stubs.h"
 #include "src/api-arguments.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 626 matching lines @@
   // Or              number_of_captures <= offsets vector size / 2 - 1
   STATIC_ASSERT(Isolate::kJSRegexpStaticOffsetsVectorSize >= 2);
   __ cmpl(rdx, Immediate(Isolate::kJSRegexpStaticOffsetsVectorSize / 2 - 1));
   __ j(above, &runtime);
 
   // Reset offset for possibly sliced string.
   __ Set(r14, 0);
   __ movp(rdi, args.GetArgumentOperand(SUBJECT_STRING_ARGUMENT_INDEX));
   __ JumpIfSmi(rdi, &runtime);
   __ movp(r15, rdi);  // Make a copy of the original subject string.
-  __ movp(rbx, FieldOperand(rdi, HeapObject::kMapOffset));
-  __ movzxbl(rbx, FieldOperand(rbx, Map::kInstanceTypeOffset));
   // rax: RegExp data (FixedArray)
   // rdi: subject string
   // r15: subject string
   // Handle subject string according to its encoding and representation:
   // (1) Sequential two byte?  If yes, go to (9).
-  // (2) Sequential one byte?  If yes, go to (6).
-  // (3) Anything but sequential or cons?  If yes, go to (7).
-  // (4) Cons string.  If the string is flat, replace subject with first string.
-  //     Otherwise bailout.
-  // (5a) Is subject sequential two byte?  If yes, go to (9).
-  // (5b) Is subject external?  If yes, go to (8).
-  // (6) One byte sequential.  Load regexp code for one byte.
+  // (2) Sequential one byte?  If yes, go to (5).
+  // (3) Sequential or cons?  If not, go to (6).
+  // (4) Cons string.  If the string is flat, replace subject with first string
+  //     and go to (1). Otherwise bail out to runtime.
+  // (5) One byte sequential.  Load regexp code for one byte.
   // (E) Carry on.
   /// [...]
 
   // Deferred code at the end of the stub:
-  // (7) Not a long external string?  If yes, go to (10).
-  // (8) External string.  Make it, offset-wise, look like a sequential string.
-  // (8a) Is the external string one byte?  If yes, go to (6).
-  // (9) Two byte sequential.  Load regexp code for one byte. Go to (E).
+  // (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 (5a).
+  // (11) Sliced string.  Replace subject with parent. Go to (1).
 
-  Label seq_one_byte_string /* 6 */, seq_two_byte_string /* 9 */,
-        external_string /* 8 */, check_underlying /* 5a */,
-        not_seq_nor_cons /* 7 */, check_code /* E */,
-        not_long_external /* 10 */;
+  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);
+  __ movp(rbx, FieldOperand(rdi, HeapObject::kMapOffset));
+  __ movzxbl(rbx, FieldOperand(rbx, Map::kInstanceTypeOffset));
 
   // (1) Sequential two byte?  If yes, go to (9).
   __ andb(rbx, Immediate(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 (6).
+  // (2) Sequential one byte?  If yes, go to (5).
   // Any other sequential string must be one byte.
   __ andb(rbx, Immediate(kIsNotStringMask |
                          kStringRepresentationMask |
                          kShortExternalStringMask));
-  __ j(zero, &seq_one_byte_string, Label::kNear);  // Go to (6).
+  __ j(zero, &seq_one_byte_string, Label::kNear);  // Go to (5).
 
-  // (3) Anything but sequential or cons?  If yes, go to (7).
+  // (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);
   STATIC_ASSERT(kIsNotStringMask > kExternalStringTag);
   STATIC_ASSERT(kShortExternalStringTag > kExternalStringTag);
   __ cmpp(rbx, Immediate(kExternalStringTag));
-  __ j(greater_equal, &not_seq_nor_cons);  // Go to (7).
+  __ 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.
   __ CompareRoot(FieldOperand(rdi, ConsString::kSecondOffset),
                  Heap::kempty_stringRootIndex);
   __ j(not_equal, &runtime);
   __ movp(rdi, FieldOperand(rdi, ConsString::kFirstOffset));
-  __ bind(&check_underlying);
-  __ movp(rbx, FieldOperand(rdi, HeapObject::kMapOffset));
-  __ movp(rbx, FieldOperand(rbx, Map::kInstanceTypeOffset));
+  __ jmp(&check_underlying);
 
-  // (5a) Is subject sequential two byte?  If yes, go to (9).
-  __ testb(rbx, Immediate(kStringRepresentationMask | kStringEncodingMask));
-  STATIC_ASSERT((kSeqStringTag | kTwoByteStringTag) == 0);
-  __ j(zero, &seq_two_byte_string);  // Go to (9).
-  // (5b) Is subject external?  If yes, go to (8).
-  __ testb(rbx, Immediate(kStringRepresentationMask));
-  // The underlying external string is never a short external string.
-  STATIC_ASSERT(ExternalString::kMaxShortLength < ConsString::kMinLength);
-  STATIC_ASSERT(ExternalString::kMaxShortLength < SlicedString::kMinLength);
-  __ j(not_zero, &external_string);  // Go to (8)
-
-  // (6) One byte sequential.  Load regexp code for one byte.
+  // (5) One byte sequential.  Load regexp code for one byte.
   __ bind(&seq_one_byte_string);
   // rax: RegExp data (FixedArray)
   __ movp(r11, FieldOperand(rax, JSRegExp::kDataOneByteCodeOffset));
   __ Set(rcx, 1);  // Type is one byte.
 
   // (E) Carry on.  String handling is done.
   __ bind(&check_code);
   // r11: irregexp code
   // Check that the irregexp code has been generated for the actual string
   // encoding. If it has, the field contains a code object otherwise it contains
@@ skipping 226 matching lines @@
   __ j(equal, &runtime);
 
   // For exception, throw the exception again.
   __ TailCallRuntime(Runtime::kRegExpExecReThrow);
 
   // Do the runtime call to execute the regexp.
   __ bind(&runtime);
   __ TailCallRuntime(Runtime::kRegExpExec);
 
   // Deferred code for string handling.
-  // (7) Not a long external string?  If yes, go to (10).
+  // (6) Long external string?  If not, go to (10).
   __ bind(&not_seq_nor_cons);
   // Compare flags are still set from (3).
   __ j(greater, &not_long_external, Label::kNear);  // Go to (10).
 
-  // (8) External string.  Short external strings have been ruled out.
+  // (7) External string.  Short external strings have been ruled out.
   __ bind(&external_string);
   __ movp(rbx, FieldOperand(rdi, HeapObject::kMapOffset));
   __ movzxbl(rbx, FieldOperand(rbx, Map::kInstanceTypeOffset));
   if (FLAG_debug_code) {
     // Assert that we do not have a cons or slice (indirect strings) here.
     // Sequential strings have already been ruled out.
     __ testb(rbx, Immediate(kIsIndirectStringMask));
     __ Assert(zero, kExternalStringExpectedButNotFound);
   }
   __ movp(rdi, FieldOperand(rdi, ExternalString::kResourceDataOffset));
   // Move the pointer so that offset-wise, it looks like a sequential string.
   STATIC_ASSERT(SeqTwoByteString::kHeaderSize == SeqOneByteString::kHeaderSize);
   __ subp(rdi, Immediate(SeqTwoByteString::kHeaderSize - kHeapObjectTag));
   STATIC_ASSERT(kTwoByteStringTag == 0);
-  // (8a) Is the external string one byte?  If yes, go to (6).
+  // (8) Is the external string one byte?  If yes, go to (5).
   __ testb(rbx, Immediate(kStringEncodingMask));
-  __ j(not_zero, &seq_one_byte_string);  // Goto (6).
+  __ j(not_zero, &seq_one_byte_string);  // Go to (5).
 
   // rdi: subject string (flat two-byte)
   // rax: RegExp data (FixedArray)
-  // (9) Two byte sequential.  Load regexp code for one byte.  Go to (E).
+  // (9) Two byte sequential.  Load regexp code for two byte.  Go to (E).
   __ bind(&seq_two_byte_string);
   __ movp(r11, FieldOperand(rax, JSRegExp::kDataUC16CodeOffset));
   __ Set(rcx, 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);
   __ testb(rbx, Immediate(kIsNotStringMask | kShortExternalStringMask));
   __ j(not_zero, &runtime);
 
-  // (11) Sliced string.  Replace subject with parent. Go to (5a).
+  // (11) Sliced string.  Replace subject with parent. Go to (1).
   // Load offset into r14 and replace subject string with parent.
   __ SmiToInteger32(r14, FieldOperand(rdi, SlicedString::kOffsetOffset));
   __ movp(rdi, FieldOperand(rdi, SlicedString::kParentOffset));
   __ jmp(&check_underlying);
 #endif  // V8_INTERPRETED_REGEXP
 }
 
 
 static int NegativeComparisonResult(Condition cc) {
   DCHECK(cc != equal);
@@ skipping 4565 matching lines @@
                            kStackUnwindSpace, nullptr, return_value_operand,
                            NULL);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64