On Apr 15, 2011, at 3:34 PM, Eric Botcazou wrote: >> The problem this patch fixes is that combine_simplify_rtx() prefers to >> return an expression (say, <xor (a) (b)>) even when a comparison is >> prefered (say, <neq (xor (a) (b)) 0>). Expressions are not recognized as >> valid conditions of if_then_else for most targets, so combiner misses a >> potential optimization. This patch makes combine_simplify_rtx() aware of >> the context it was invoked in, and, when appropriate, does not discourage >> it from returning a conditional. > > Btw, this is very likely also valid for targets with STORE_FLAG_VALUE == -1 > so > the same IN_COND short-circuit would need to be added a few lines below in > combine_simplify_rtx. But this would need to be tested. Do you happen to > have access to such a target, e.g. m68k?
Hm, I didn't notice that one, thanks! I have access to m68k (ColdFire, tbp) and will test this change there before committing. -- Maxim Kuvyrkov Mentor Graphics / CodeSourcery
