Updates:
Status: PendingFurtherInfo
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Comment #7 on issue 2124 by [email protected]: Register Allocator in
some condition doesn't handle FixedTemp correctly
http://code.google.com/p/v8/issues/detail?id=2124
Not sure I understand your comment #6 correctly. Do you by chance have an
example that triggers the problem in current V8?
After further discussion with vegorov@, I think it is not an immediate
problem, but agree that it should be addressed if we decide to use fixed
temps in the way that your patch does.
Another idea: The policy WRITABLE_REGISTER is probably obsolete by now. The
problem could be solved by getting rid of it. I think it would be worth
looking at removing it completely in order to simplify the register
allocator:
UseTempRegister can be replaced by UseRegisterAtStart + TempRegister where
we give the temp register a hint to use the same register as the input if
possible. If the temp does not get the same register, insert a move
explicitly in the code generator at the very beginning of the instruction.
(Originally, we did not have the UseRegisterAtStart-Policy, so
UseTempRegister was introduced to reuse an input operand register as a
temp.)
I'm un-assigning this issue for now until we decide what action to take.
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