[PATCH] gen_lowpart_no_emit RTL hook
Paolo Bonzini
paolo.bonzini@lu.unisi.ch
Mon Mar 21 09:36:00 GMT 2005
This is another patch to prepare moving transformations from
combine.c to simplify-rtx.c. gen_lowpart can emit instructions via
copy_to_reg or force_reg, and thus simplify-rtx.c must resort to either
gen_lowpart_common or gen_lowpart_SUBREG.
However, combine.c defines a version of gen_lowpart that is more
aggressive in generating possibly invalid rtx, but will not generate new
pseudos. When transformations are moved to simplify-rtx.c, it is valid
to use this version of gen_lowpart.
So, this patch turns this ``common'' (it occurs 3 times) pattern found
in simplify-rtx.c, into a different RTL hook:
rtx x = gen_lowpart_common (mode, op0);
if (x)
return x;
if (mode != GET_MODE (op0) && GET_MODE (op0) != VOIDmode)
return gen_lowpart_SUBREG (mode, op0);
return op0;
This patch introduces no difference in behavior. Subsequent patches
will involve:
- using gen_lowpart_for_combine as combine's gen_lowpart_no_emit hook
- investigating using lowpart_subreg instead of gen_lowpart_SUBREG.
- investigating merging gen_lowpart_if_possible with the generic
implementation of the hook
Bootstrapped/regtested powerpc-apple-darwin7.8.0, ok for mainline?
Paolo
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