Change generated code for substring not to bail out to runtime system.

There is no need to bail out to runtime system when creating sliced strings of external strings since the string content is unimportant.

Review URL: http://codereview.chromium.org/8513016

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10012 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

diff --git a/src/arm/code-stubs-arm.cc b/src/arm/code-stubs-arm.cc
index b37855b8e0929af23380bce6da69c736fd054954..9e6f7596e7fc60131cdaf956d07567854514e74b 100644 (file)
--- a/src/arm/code-stubs-arm.cc
+++ b/src/arm/code-stubs-arm.cc
@@ -5815,15 +5815,12 @@ void SubStringStub::Generate(MacroAssembler* masm) {
     // r3: from index (untagged smi)
     // r6 (a.k.a. to): to (smi)
     // r7 (a.k.a. from): from offset (smi)
-    Label allocate_slice, sliced_string, seq_string;
-    STATIC_ASSERT(kSeqStringTag == 0);
-    __ tst(r1, Operand(kStringRepresentationMask));
-    __ b(eq, &seq_string);
+    Label allocate_slice, sliced_string, seq_or_external_string;
+    // If the string is not indirect, it can only be sequential or external.
     STATIC_ASSERT(kIsIndirectStringMask == (kSlicedStringTag & kConsStringTag));
     STATIC_ASSERT(kIsIndirectStringMask != 0);
     __ tst(r1, Operand(kIsIndirectStringMask));
-    // External string.  Jump to runtime.
-    __ b(eq, &runtime);
+    __ b(eq, &seq_or_external_string);
 
     __ tst(r1, Operand(kSlicedNotConsMask));
     __ b(ne, &sliced_string);
@@ -5842,8 +5839,8 @@ void SubStringStub::Generate(MacroAssembler* masm) {
     __ ldr(r5, FieldMemOperand(r0, SlicedString::kParentOffset));
     __ jmp(&allocate_slice);
 
-    __ bind(&seq_string);
-    // Sequential string.  Just move string to the right register.
+    __ bind(&seq_or_external_string);
+    // Sequential or external string.  Just move string to the correct register.
     __ mov(r5, r0);
 
     __ bind(&allocate_slice);

diff --git a/src/ia32/code-stubs-ia32.cc b/src/ia32/code-stubs-ia32.cc
index 23bea4f8568ce2cebeccf8212be82343e75e4d29..8d30447b94d424ce7dcf3e7ad229fb6fb0ad00e8 100644 (file)
--- a/src/ia32/code-stubs-ia32.cc
+++ b/src/ia32/code-stubs-ia32.cc
@@ -5973,18 +5973,15 @@ void SubStringStub::Generate(MacroAssembler* masm) {
     // ebx: instance type
     // ecx: sub string length
     // edx: from index (smi)
-    Label allocate_slice, sliced_string, seq_string;
+    Label allocate_slice, sliced_string, seq_or_external_string;
     __ cmp(ecx, SlicedString::kMinLength);
     // Short slice.  Copy instead of slicing.
     __ j(less, &copy_routine);
-    STATIC_ASSERT(kSeqStringTag == 0);
-    __ test(ebx, Immediate(kStringRepresentationMask));
-    __ j(zero, &seq_string, Label::kNear);
+    // If the string is not indirect, it can only be sequential or external.
     STATIC_ASSERT(kIsIndirectStringMask == (kSlicedStringTag & kConsStringTag));
     STATIC_ASSERT(kIsIndirectStringMask != 0);
     __ test(ebx, Immediate(kIsIndirectStringMask));
-    // External string.  Jump to runtime.
-    __ j(zero, &runtime);
+    __ j(zero, &seq_or_external_string, Label::kNear);
 
     Factory* factory = masm->isolate()->factory();
     __ test(ebx, Immediate(kSlicedNotConsMask));
@@ -6002,8 +5999,8 @@ void SubStringStub::Generate(MacroAssembler* masm) {
     __ mov(edi, FieldOperand(eax, SlicedString::kParentOffset));
     __ jmp(&allocate_slice, Label::kNear);
 
-    __ bind(&seq_string);
-    // Sequential string.  Just move string to the right register.
+    __ bind(&seq_or_external_string);
+    // Sequential or external string.  Just move string to the correct register.
     __ mov(edi, eax);
 
     __ bind(&allocate_slice);

diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index bf50869ed90f1a381160756ecacbd633c456a1b2..62be27e6433e0db66a1c8d25a3214c20466fbb7a 100644 (file)
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -4912,18 +4912,15 @@ void SubStringStub::Generate(MacroAssembler* masm) {
     // rbx: instance type
     // rcx: sub string length
     // rdx: from index (smi)
-    Label allocate_slice, sliced_string, seq_string;
+    Label allocate_slice, sliced_string, seq_or_external_string;
     __ cmpq(rcx, Immediate(SlicedString::kMinLength));
     // Short slice.  Copy instead of slicing.
     __ j(less, &copy_routine);
-    STATIC_ASSERT(kSeqStringTag == 0);
-    __ testb(rbx, Immediate(kStringRepresentationMask));
-    __ j(zero, &seq_string, Label::kNear);
+    // If the string is not indirect, it can only be sequential or external.
     STATIC_ASSERT(kIsIndirectStringMask == (kSlicedStringTag & kConsStringTag));
     STATIC_ASSERT(kIsIndirectStringMask != 0);
     __ testb(rbx, Immediate(kIsIndirectStringMask));
-    // External string.  Jump to runtime.
-    __ j(zero, &runtime);
+    __ j(zero, &seq_or_external_string, Label::kNear);
 
     __ testb(rbx, Immediate(kSlicedNotConsMask));
     __ j(not_zero, &sliced_string, Label::kNear);
@@ -4940,8 +4937,8 @@ void SubStringStub::Generate(MacroAssembler* masm) {
     __ movq(rdi, FieldOperand(rax, SlicedString::kParentOffset));
     __ jmp(&allocate_slice, Label::kNear);
 
-    __ bind(&seq_string);
-    // Sequential string.  Just move string to the right register.
+    __ bind(&seq_or_external_string);
+    // Sequential or external string.  Just move string to the correct register.
     __ movq(rdi, rax);
 
     __ bind(&allocate_slice);