On 10/04/2011 08:42 AM, Joseph S. Myers wrote: > On Tue, 4 Oct 2011, Ilya Tocar wrote: > >> Hi everyone, >> >> This patch fixes PR 50038 (redundant zero extensions) by modifying >> implicit-zee pass >> to also remove unneeded zero extensions from QImode to SImode. > > Hardcoding particular modes like this in the target-independent parts of > the compiler is fundamentally ill-conceived. Right now it hardcodes the > (SImode, DImode) pair. You're adding hardcoding of (QImode, SImode) as > well. But really it should consider all pairs of (integer mode, wider > integer mode), with the machine description (or target hooks) determining > which pairs are relevant on a particular target. Changing it not to > hardcode particular modes would be better than adding a second pair. >
That along with not hard-coding ZERO_EXTEND. Both MIPS and Alpha have much the same free operations, but with SIGN_EXTEND. I remember rejecting one iteration of this pass with this hard-coded, but the pass was apparently approved by someone else without that being corrected. r~
