Richard Biener <richard.guent...@gmail.com> writes: > On Wed, Jul 30, 2014 at 12:49 PM, Prathamesh Kulkarni > <bilbotheelffri...@gmail.com> wrote: >> Hi, >> Sorry to ask a stupid question, but I am having issues writing patterns >> involving casts. I am trying to write patterns from simplify_rotate. >> >> Could you show me how to write a patterns that involve >> casts ? >> for eg: >> ((T) ((T2) X << CNT1)) + ((T) ((T2) X >> CNT2)) iff CNT1 + CNT2 == B >> T -> some unsigned type with bitsize B, and some type T2 wider than T. >> How to express this in the pattern ? > > [copying gcc@ because of the syntax stuff] > > for example with (leaving captures as the appear in the pattern above) > > (match_and_simplify > (plus (convert@2 (lshift (convert@0 X) CNT1)) > (convert (rshift (convert@1 X) CNT2))) > /* Types T2 have to match */ > (if (types_compatible_p (TREE_TYPE (@0), TREE_TYPE (@1)) > /* Type T should be unsigned. */ > && TYPE_UNSIGNED (TREE_TYPE (@2)) > /* T2 should be wider than T. */ > && TYPE_PRECISION (TREE_TYPE (@0)) > TYPE_PRECISION (TREE_TYPE (@2)) > /* CNT1 + CNT2 == B */ > && wi::eq_p (TYPE_PRECISION (TREE_TYPE (@2)), > wi::add (CNT1, CNT2)))) > (lrotate CNT1)) > > which suggests that we may want to add some type capturing / matching > so we can maybe write > > (plus (convert@T (lshift (convert@T2 X) CNT1)) > (convert (rshift (convert@T2 X) CNT2))) > (if (/* T2s will be matched automagically */ > && TYPE_UNSIGNED (@T) > && TYPE_PRECISION (@T2) > TYPE_PRECISION (@T) > && wi::eq_p (TYPE_PRECISION (@T), wi::add (CNT1, CNT2)))) > > which is less to type and supports requiring matching types. Maybe > require @T[0-9]+ here thus use @T0 and disallow plain @T. We could > then also use @T for the implicitely "captured" outermost type we > refer to as plain 'type' right now.
Would it also be worth trying to push more of the type properties into the pattern, a bit like md predicates? (Not the same syntax though, obviously.) Was just thinking that postponing things like "TYPE_UNSIGNED (@T)" until the whole tree has been matched could be inefficient in some cases. Might be going over old ground though, sorry. Richard
