On Sun, 24 Jul 2016, Bin.Cheng wrote: > Hi, > I ran into a problem that C frontend (in function > build_conditional_expr) creates expression like (C_MAYBE_CONST_EXPR > (NULL, x + const)). The inner expression (and its operands) have > unsigned int type. After that, the expression needs to be casted to > result type which is unsigned short. In this case, > convert_to_integer/convert_to_integer_1 doesn't fold into > C_MAYBE_CONST_EXPR and just returns (unsigned > short)(C_MAYBE_CONST_EXPR (NULL, x + const)), as a result, (unsigned > short)(x + const) won't be simplified as (unsigned short)x + const. > My questions are, 1) Is it possible to fold type conversion into > C_MAYBE_CONST_EXPR's inner expression in convert_to_integer_1? 2) If > not, looks like there are couple of places the mentioned fold can be > done, for example, after stripping C_MAYBE_CONST_EXPR and before (or > during) gimplify. So which place is preferred?
The folding should occur from, or after, c_fully_fold. In general, convert_to_* should do less optimization; the optimizations there should be moved to the match-and-simplify infrastructure. -- Joseph S. Myers jos...@codesourcery.com
