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sparse contains some code to simplify an AND masking
followed by a truncating cast.
However, this simplification is problematic because it
doesn't keep the sizes consistent. For example, code like:
and.32 %r3 <- %r2, $0x7fff
trunc.16 %r4 <- (32) %r3
will be discarded with %r3 used in place of %r4.
This is correct in the mathematical sense but %r4 had a size
of 16 while %r3 has a size of 32, so using %r3 in place of %r4
will make the sizes inconsistent with unexpected consequences.
We can more or less fix this by using another transformation
that preserve the sizes:
trunc.16 %r3 <- (32) %r2
and.16 %r4 <- %r3, $0x7fff
which in itself doesn't optimize anything but:
1) the mask may be smaller
2) may trigger other simplification with the TRUNC or the AND.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
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