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Re: RFC patch: invariant addresses too cheap

On 10/31/2009 12:14 PM, Richard Guenther wrote:
On Sat, Oct 31, 2009 at 11:58 AM, Paolo Bonzini<bonzini@gnu.org> wrote:
On 10/31/2009 10:57 AM, Richard Sandiford wrote: 

So either I need to hack MIPS so that
2 is cheap and 3+ is "expensive", or we need some better way
of determining this.


-  return mips_address_insns (addr, SImode, false);
+  int insns = mips_address_insns (addr, SImode, false);
+  return insns == 1 ? 1 : COSTS_N_INSNS (insns - 1);

?

I don't think sticking an x86-specific magic number in the
middle of generic code is acceptable, regardless of how big
the comment above it is. ;)


That's why I suggested using "<= COSTS_N_INSNS (1) / 2" instead of "<  3".
  Also ix86-specific calibration, but not so brutally. :-)


But then you should document that address-cost is supposed to be
insn-cost based.  Otherwise comparing apples with oranges doesn't
make sense, even if it might look less magic to you.

That's true.

Paolo

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