On 02/12/15 00:01, Bin.Cheng wrote:
Cool that we are trying to simplify type conversion using generic
match facility. I have thought about type promotion in match.pd too.
match.pd really feels like a meta-language which describes how to
combine gimple or generic statements.
For example, (unsigned long long)(unsigned long)(int_expr), if we can
prove int_expr is always positive (in my case, this is from vrp
information), then the first conversion can be saved. This is another
way for (and related? I didn't look at the code) the sign/zero
extension elimination work using VRP I suppose?
In theory, given VRP information attached to an SSA_NAME you could query
that information in the conditional part of the match.pd pattern.
Another patch I'm working on is best described as detecting cases where
an outer bit-and masks off all the bits outside the innermost operand's
type. Under the right conditions, this also allows for narrowing.
Jeff
