> 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? -- Eric Botcazou
