[Patch] PR68137, drop constant overflow flag in adjust_range_with_scev when possible

As reported by pr68137 and pr68326, r230150 caused new issues. Those ICEs are caused by adjust_range_with_scev getting range with overflowed constants min or max. So given there are too many places to generate OVF, we do a check in adjust_range_with_scev, to drop OVF flag when it's uncessary.

Re: [Patch] PR68137, drop constant overflow flag in adjust_range_with_scev when possible

On Mon, 23 Nov 2015, Jiong Wang wrote: > As reported by pr68137 and pr68326, r230150 caused new issues. > > Those ICEs are caused by adjust_range_with_scev getting range with > overflowed constants min or max. So given there are too many places to > generate OVF, we do a check in