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

src/arm/code-stubs-arm.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_ARM
 
 #include "src/code-stubs.h"
 #include "src/api-arguments.h"
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
@@ skipping 1559 matching lines @@
   STATIC_ASSERT(kSmiTagSize + kSmiShiftSize == 1);
   STATIC_ASSERT(Isolate::kJSRegexpStaticOffsetsVectorSize >= 2);
   __ cmp(r2, Operand(Isolate::kJSRegexpStaticOffsetsVectorSize - 2));
   __ b(hi, &runtime);
 
   // Reset offset for possibly sliced string.
   __ mov(r9, Operand::Zero());
   __ ldr(subject, MemOperand(sp, kSubjectOffset));
   __ JumpIfSmi(subject, &runtime);
   __ mov(r3, subject);  // Make a copy of the original subject string.
-  __ ldr(r0, FieldMemOperand(subject, HeapObject::kMapOffset));
-  __ ldrb(r0, FieldMemOperand(r0, Map::kInstanceTypeOffset));
   // subject: subject string
   // r3: subject string
-  // r0: subject string instance type
   // regexp_data: RegExp data (FixedArray)
   // Handle subject string according to its encoding and representation:
-  // (1) Sequential string?  If yes, go to (5).
-  // (2) Anything but sequential or cons?  If yes, go to (6).
-  // (3) Cons string.  If the string is flat, replace subject with first string.
-  //     Otherwise bailout.
-  // (4) Is subject external?  If yes, go to (7).
-  // (5) Sequential string.  Load regexp code according to encoding.
+  // (1) Sequential string?  If yes, go to (4).
+  // (2) Sequential or cons?  If not, go to (5).
+  // (3) Cons string.  If the string is flat, replace subject with first string
+  //     and go to (1). Otherwise bail out to runtime.
+  // (4) Sequential string.  Load regexp code according to encoding.
   // (E) Carry on.
   /// [...]
 
   // Deferred code at the end of the stub:
-  // (6) Not a long external string?  If yes, go to (8).
-  // (7) External string.  Make it, offset-wise, look like a sequential string.
-  //     Go to (5).
-  // (8) Short external string or not a string?  If yes, bail out to runtime.
-  // (9) Sliced string.  Replace subject with parent.  Go to (4).
+  // (5) Long external string?  If not, go to (7).
+  // (6) External string.  Make it, offset-wise, look like a sequential string.
+  //     Go to (4).
+  // (7) Short external string or not a string?  If yes, bail out to runtime.
+  // (8) Sliced string.  Replace subject with parent.  Go to (1).
 
-  Label seq_string /* 5 */, external_string /* 7 */,
-        check_underlying /* 4 */, not_seq_nor_cons /* 6 */,
-        not_long_external /* 8 */;
+  Label seq_string /* 4 */, external_string /* 6 */, check_underlying /* 1 */,
+      not_seq_nor_cons /* 5 */, not_long_external /* 7 */;
 
-  // (1) Sequential string?  If yes, go to (5).
+  __ bind(&check_underlying);
+  __ ldr(r0, FieldMemOperand(subject, HeapObject::kMapOffset));
+  __ ldrb(r0, FieldMemOperand(r0, Map::kInstanceTypeOffset));
+
+  // (1) Sequential string?  If yes, go to (4).
   __ and_(r1,
           r0,
           Operand(kIsNotStringMask |
                   kStringRepresentationMask |
                   kShortExternalStringMask),
           SetCC);
   STATIC_ASSERT((kStringTag | kSeqStringTag) == 0);
-  __ b(eq, &seq_string);  // Go to (5).
+  __ b(eq, &seq_string);  // Go to (4).
 
-  // (2) Anything but sequential or cons?  If yes, go to (6).
+  // (2) Sequential or cons?  If not, go to (5).
   STATIC_ASSERT(kConsStringTag < kExternalStringTag);
   STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
   STATIC_ASSERT(kIsNotStringMask > kExternalStringTag);
   STATIC_ASSERT(kShortExternalStringTag > kExternalStringTag);
   __ cmp(r1, Operand(kExternalStringTag));
-  __ b(ge, &not_seq_nor_cons);  // Go to (6).
+  __ b(ge, &not_seq_nor_cons);  // Go to (5).
 
   // (3) Cons string.  Check that it's flat.
   // Replace subject with first string and reload instance type.
   __ ldr(r0, FieldMemOperand(subject, ConsString::kSecondOffset));
   __ CompareRoot(r0, Heap::kempty_stringRootIndex);
   __ b(ne, &runtime);
   __ ldr(subject, FieldMemOperand(subject, ConsString::kFirstOffset));
+  __ jmp(&check_underlying);
 
-  // (4) Is subject external?  If yes, go to (7).
-  __ bind(&check_underlying);
-  __ ldr(r0, FieldMemOperand(subject, HeapObject::kMapOffset));
-  __ ldrb(r0, FieldMemOperand(r0, Map::kInstanceTypeOffset));
-  STATIC_ASSERT(kSeqStringTag == 0);
-  __ tst(r0, Operand(kStringRepresentationMask));
-  // The underlying external string is never a short external string.
-  STATIC_ASSERT(ExternalString::kMaxShortLength < ConsString::kMinLength);
-  STATIC_ASSERT(ExternalString::kMaxShortLength < SlicedString::kMinLength);
-  __ b(ne, &external_string);  // Go to (7).
-
-  // (5) Sequential string.  Load regexp code according to encoding.
+  // (4) Sequential string.  Load regexp code according to encoding.
   __ bind(&seq_string);
   // subject: sequential subject string (or look-alike, external string)
   // r3: original subject string
   // Load previous index and check range before r3 is overwritten.  We have to
   // use r3 instead of subject here because subject might have been only made
   // to look like a sequential string when it actually is an external string.
   __ ldr(r1, MemOperand(sp, kPreviousIndexOffset));
   __ JumpIfNotSmi(r1, &runtime);
   __ ldr(r3, FieldMemOperand(r3, String::kLengthOffset));
   __ cmp(r3, Operand(r1));
@@ skipping 212 matching lines @@
   // Return last match info.
   __ ldr(r0, MemOperand(sp, kLastMatchInfoOffset));
   __ add(sp, sp, Operand(4 * kPointerSize));
   __ Ret();
 
   // Do the runtime call to execute the regexp.
   __ bind(&runtime);
   __ TailCallRuntime(Runtime::kRegExpExec);
 
   // Deferred code for string handling.
-  // (6) Not a long external string?  If yes, go to (8).
+  // (5) Long external string?  If not, go to (7).
   __ bind(&not_seq_nor_cons);
   // Compare flags are still set.
-  __ b(gt, &not_long_external);  // Go to (8).
+  __ b(gt, &not_long_external);  // Go to (7).
 
-  // (7) External string.  Make it, offset-wise, look like a sequential string.
+  // (6) External string.  Make it, offset-wise, look like a sequential string.
   __ bind(&external_string);
   __ ldr(r0, FieldMemOperand(subject, HeapObject::kMapOffset));
   __ ldrb(r0, FieldMemOperand(r0, 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.
     __ tst(r0, Operand(kIsIndirectStringMask));
     __ Assert(eq, kExternalStringExpectedButNotFound);
   }
   __ ldr(subject,
          FieldMemOperand(subject, ExternalString::kResourceDataOffset));
   // Move the pointer so that offset-wise, it looks like a sequential string.
   STATIC_ASSERT(SeqTwoByteString::kHeaderSize == SeqOneByteString::kHeaderSize);
   __ sub(subject,
          subject,
          Operand(SeqTwoByteString::kHeaderSize - kHeapObjectTag));
-  __ jmp(&seq_string);    // Go to (5).
+  __ jmp(&seq_string);  // Go to (4).
 
-  // (8) Short external string or not a string?  If yes, bail out to runtime.
+  // (7) Short external string or not a string?  If yes, bail out to runtime.
   __ bind(&not_long_external);
   STATIC_ASSERT(kNotStringTag != 0 && kShortExternalStringTag !=0);
   __ tst(r1, Operand(kIsNotStringMask | kShortExternalStringMask));
   __ b(ne, &runtime);
 
-  // (9) Sliced string.  Replace subject with parent.  Go to (4).
+  // (8) Sliced string.  Replace subject with parent.  Go to (4).
   // Load offset into r9 and replace subject string with parent.
   __ ldr(r9, FieldMemOperand(subject, SlicedString::kOffsetOffset));
   __ SmiUntag(r9);
   __ ldr(subject, FieldMemOperand(subject, SlicedString::kParentOffset));
   __ jmp(&check_underlying);  // Go to (4).
 #endif  // V8_INTERPRETED_REGEXP
 }
 
 
 static void CallStubInRecordCallTarget(MacroAssembler* masm, CodeStub* stub) {
@@ skipping 3654 matching lines @@
   CallApiFunctionAndReturn(masm, api_function_address, thunk_ref,
                            kStackUnwindSpace, NULL, return_value_operand, NULL);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM