On Sun, Jul 24, 2016 at 11:04 PM, Prathamesh Kulkarni <prathamesh.kulka...@linaro.org> wrote: > On 24 July 2016 at 21:26, Bin.Cheng <amker.ch...@gmail.com> 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? > Sorry, I have a very silly question: > I don't understand how the following transform > (unsigned short) (x + const) to (unsigned short)x + const would be legal > since the operands to PLUS_EXPR in latter case would have different types > (unsigned short, unsigned) ? > I suppose in GIMPLE (and GENERIC too?) > we require rhs1 and rhs2 to have same types ? I skipped type information for the const operand, of course the const will be converted to unsigned short which is the type for computation.
Thanks, bin
