On Mon, Sep 23, 2019 at 11:56:27AM +0100, Andrew Stubbs wrote: > [(set (match_operand:DI 0 "register_operand" "=Sg,v") > (ashift:DI > (match_operand:DI 1 "gcn_alu_operand" " Sg,v") > (match_operand:SI 2 "gcn_alu_operand" " Sg,v"))) > (clobber (match_scratch:BI 3 "=cs,X"))]
> Unfortunately, the compiler (almost?) exclusively selects the second > alternative, even when this means moving the values from one register > file to the other, and then back again. > > The problem is that the scalar instruction clobbers the CC register, > which results in a "reject++" for that alternative in the LRA dump. What kind of reject? It prints a reason, too. Maybe we should make a macro/hook to never do that for your target, for those flags registers anyway. Segher
