gcc/resource.c mark_target_live_regs Question

[Mark Mitchell]

>>>>> "Brad" == Brad Lucier <lucier@math.purdue.edu> writes:

    Brad> I'm not exactly understanding all the implications of this
    Brad> discussion, but one easily gets > 200 instructions in the
    Brad> inner basic block of a 8-way butterfly FFT code used for
    Brad> bignum multiplication, and I wouldn't want all registers
    Brad> marked as live in that block.

We're talking about this in the context of delay-slot filling.

Bottom line: you're often concerned about compile-time performance on
machine-generated code, and this is one of the problematic places.
With better algorithsm, we could run faster and generate better code
-- but that's not going to happen right now, so we might as well bring
the compile-times into a reasonable range.  Plus, with the new --param
stuff, you can always crank this all the way back up if you want.

--
Mark Mitchell                   mark@codesourcery.com
CodeSourcery, LLC               http://www.codesourcery.com