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authorMichael Forney <mforney@mforney.org>2021-11-18 01:45:27 -0800
committerQuentin Carbonneaux <quentin@c9x.me>2021-11-22 18:07:50 +0100
commitbf153b359e9ce3ebef9bca899eb7ed5bd9045c11 (patch)
tree20857b60dfd9a0f5bb98dee40a1f4b140ba76447 /minic/.gitignore
parentb0f16dad64d14f36ffe235b2e9cca96aa3ce35ba (diff)
downloadroux-bf153b359e9ce3ebef9bca899eb7ed5bd9045c11.tar.gz
reuse previous address constants in fold()
parseref() has code to reuse address constants, but this is not
done in other passes such as fold or isel. Introduce a new function
newcon() which takes a Con and returns a Ref for that constant, and
use this whenever creating address constants.

This is necessary to fix folding of address constants when one
operand is already folded. For example, in

	%a =l add $x, 1
	%b =l add %a, 2
	%c =w loadw %b

%a and %b were folded to $x+1 and $x+3 respectively, but then the
second add is visited again since it uses %a. This gets folded to
$x+3 as well, but as a new distinct constant. This results in %b
getting labeled as bottom instead of either constant, disabling the
replacement of %b by a constant in subsequent instructions (such
as the loadw).
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