On 10 okt 2006, at 11:09, Florian Klaempfl wrote:
Also, do you actually insert goto/label nodes? That would
degrade the performance of the register variable assignment
because of
the current limitations concerning flow analysis (i.e., for
sufficiently
complex routines, the tail recursion optimization may currently
result
in performance degradation rather than improvement compared to using
regvars without it).
The recursive call is usually inside an if anyways so the ssa
optimizer is lost
anyways, no?
For the part inside the if: yes. But not for the part coming before
it. What's more important however is that goto/label not only removes
the usage of SSA, it also means that all register variables are
allocated at the start of the function and only freed at the end.
Without goto/label, register variables are only allocated between
their first and last use (usage in a loop means allocation until the
end of that loop).
BTW: Does the assembler optimizer track flag usage? Then we could
remove some of
the
movl %esi,%eax
incl %eax
like pairs.
There's a FlagsUsed field in the ttaiprop record which is set to true
if the flags result of that instruction is used.
Jonas
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