Capture register clearing on loop iteration

src/regexp-macro-assembler-ia32.cc

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@@ skipping 910 matching lines @@
                                                               int cp_offset) {
   if (cp_offset == 0) {
     __ mov(register_location(reg), edi);
   } else {
     __ lea(eax, Operand(edi, cp_offset * char_size()));
     __ mov(register_location(reg), eax);
   }
 }
 
 
+void RegExpMacroAssemblerIA32::ClearRegister(int reg) {
+  __ mov(register_location(reg), esi);

[Lasse Reichstein, 2009/01/14 08:38:34]

The esi register does not hold the needed value (one character before the start
of the string) but instead it points to the end of the string.
A cleared register would be seen as captured, with a position at the end of the
string.

Code that, I think, should trigger this:
 var m = /(?:(a)|b)*/.exec("ab");
 // m[1] should be null, it is "".
Otherwise a C-level test should show the difference in returned value for the
capture registers (2 instead of -1).

The correct value is computed in GetCode(), in the entry part, where we
initialize the capture registers. I suggest storing it somewhere safe (e.g., as
a "local variable" in the stack frame) until it's needed.

[Christian Plesner Hansen, 2009/01/14 11:31:35]

Fixed

+}
+
+
 void RegExpMacroAssemblerIA32::WriteStackPointerToRegister(int reg) {
   __ mov(register_location(reg), backtrack_stackpointer());
 }
 
 
 // Private methods:
 
 
 static unibrow::Mapping<unibrow::Ecma262Canonicalize> canonicalize;
 
@@ skipping 258 matching lines @@
 
 
 void RegExpMacroAssemblerIA32::LoadConstantBufferAddress(Register reg,
                                                          ArraySlice* buffer) {
   __ mov(reg, buffer->array());
   __ add(Operand(reg), Immediate(buffer->base_offset()));
 }
 
 #undef __
 }}  // namespace v8::internal