VM: Optimize RegExp.matchAsPrefix(...) by generating a sticky RegExp specialization.

runtime/vm/intrinsifier_x64.cc

Index: runtime/vm/intrinsifier_x64.cc
diff --git a/runtime/vm/intrinsifier_x64.cc b/runtime/vm/intrinsifier_x64.cc
index b888804ec48014899ce266223dccc7c3d406fc48..9f6f053fb132aa5cde0413227b9075429b11bf2d 100644
--- a/runtime/vm/intrinsifier_x64.cc
+++ b/runtime/vm/intrinsifier_x64.cc
@@ -2193,7 +2193,7 @@ void Intrinsifier::TwoByteString_equality(Assembler* assembler) {
 
 
 void Intrinsifier::RegExp_ExecuteMatch(Assembler* assembler) {

[erikcorry, 2016/11/17 13:56:17]

Can't RegExp_ExecuteMatch and RegExp_ExecuteMatchSticky not both call a helper
with a bool argument?

[Vyacheslav Egorov (Google), 2016/11/17 16:51:33]

In this case code below would have to check for boolean argument. It makes entry
into regexp slower. 

-  if (FLAG_interpret_irregexp) return;
+  if (FLAG_interpret_irregexp || FLAG_precompiled_runtime) return;

[rmacnak, 2016/11/17 00:49:52]

Why add this? FLAG_interpret_irregexp should already be compile-time true in the
AOT runtime.

[Vyacheslav Egorov (Google), 2016/11/17 16:51:33]

There was a code somewhere that checked both so I added it here too to match. 

Instead I should remove it there.

 
   static const intptr_t kRegExpParamOffset = 3 * kWordSize;
   static const intptr_t kStringParamOffset = 2 * kWordSize;
@@ -2211,7 +2211,41 @@ void Intrinsifier::RegExp_ExecuteMatch(Assembler* assembler) {
   __ LoadClassId(RDI, RDI);
   __ SubImmediate(RDI, Immediate(kOneByteStringCid));
   __ movq(RAX, FieldAddress(RBX, RDI, TIMES_8,
-                            RegExp::function_offset(kOneByteStringCid)));
+                            RegExp::function_offset(kOneByteStringCid,
+                                                    /*sticky=*/false)));
+
+  // Registers are now set up for the lazy compile stub. It expects the function
+  // in RAX, the argument descriptor in R10, and IC-Data in RCX.
+  __ xorq(RCX, RCX);
+
+  // Tail-call the function.
+  __ movq(CODE_REG, FieldAddress(RAX, Function::code_offset()));
+  __ movq(RDI, FieldAddress(RAX, Function::entry_point_offset()));
+  __ jmp(RDI);
+}
+
+
+void Intrinsifier::RegExp_ExecuteMatchSticky(Assembler* assembler) {
+  if (FLAG_interpret_irregexp || FLAG_precompiled_runtime) return;
+
+  static const intptr_t kRegExpParamOffset = 3 * kWordSize;
+  static const intptr_t kStringParamOffset = 2 * kWordSize;
+  // start_index smi is located at offset 1.
+
+  // Incoming registers:
+  // RAX: Function. (Will be loaded with the specialized matcher function.)
+  // RCX: Unknown. (Must be GC safe on tail call.)
+  // R10: Arguments descriptor. (Will be preserved.)
+
+  // Load the specialized function pointer into RAX. Leverage the fact the
+  // string CIDs as well as stored function pointers are in sequence.
+  __ movq(RBX, Address(RSP, kRegExpParamOffset));
+  __ movq(RDI, Address(RSP, kStringParamOffset));
+  __ LoadClassId(RDI, RDI);
+  __ SubImmediate(RDI, Immediate(kOneByteStringCid));
+  __ movq(RAX, FieldAddress(RBX, RDI, TIMES_8,
+                            RegExp::function_offset(kOneByteStringCid,
+                                                    /*sticky=*/true)));
 
   // Registers are now set up for the lazy compile stub. It expects the function
   // in RAX, the argument descriptor in R10, and IC-Data in RCX.