[cfe-commits] [Patch] PR11179 - Update StmtPrinter to not complain on some IntegerLiteral types

[Abramo Bagnara]

Il 03/11/2011 00:16, Richard Trieu ha scritto:
> On Wed, Nov 2, 2011 at 3:51 PM, Abramo Bagnara <abramo.bagnara at gmail.com
> <mailto:abramo.bagnara at gmail.com>> wrote:
> 
>     Il 02/11/2011 03:21, Richard Trieu ha scritto:
>     > On Mon, Oct 24, 2011 at 7:30 AM, Douglas Gregor <dgregor at apple.com
>     <mailto:dgregor at apple.com>
>     > <mailto:dgregor at apple.com <mailto:dgregor at apple.com>>> wrote:
>     >
>     >
>     >     On Oct 20, 2011, at 5:36 PM, Chandler Carruth wrote:
>     >
>     >>     On Thu, Oct 20, 2011 at 5:12 PM, Richard Trieu
>     <rtrieu at google.com <mailto:rtrieu at google.com>
>     >>     <mailto:rtrieu at google.com <mailto:rtrieu at google.com>>> wrote:
>     >>
>     >>         Should Clang be printing suffixes that are accepted only with
>     >>         certain flags?
>     >>
>     >>
>     >>     I think this is an interesting policy decision. I'd love to hear
>     >>     Doug's thoughts on it.
>     >>
>     >>     It seems fine to me for Clang, when running with -fms-extensions,
>     >>     to suggest fixes even if only valid for -fms-extensions. Clearly
>     >>     if there is a generic suggestion that could be made, that
>     would be
>     >>     a preferred alternative. For example, '__asm__' should be
>     >>     suggested before 'asm'.
>     >
>     >     I think it's fine for Clang to print suffixes that are only
>     accepted
>     >     with certain flags. Presumably, you should never get an
>     >     IntegerLiteral of type __int128_t unless you're in a dialect that
>     >     supports parsing it.
>     >
>     >     … except that we cheat when we're building template arguments,
>     >     because it was convenient. That cheating could be eliminated by
>     >     encoding integer literal values directly within
>     >     SubstNonTypeTemplateParmExpr.
>     >
>     >     - Doug
>     >
>     >
>     > New patch.  Changes as follows:
>     > Add int128 and uint128 suffixes (i128 and Ui128) to StmtPrinter.
>      short
>     > and unsigned short will get to llvm_unreachable
>     > Add assert to IntergerLiteral to prevent creation with type short or
>     > unsigned short
>     > Fix comment in IntegerLiteral to say that int128 and uint128 are
>     > acceptable types
>     > Change BuildExpressFromIntegralTemplateArgument to give a proper Expr.
>     >  For negative numbers, use UnaryOperator of IntegerLiteral.  For short
>     > and unsigned short, ImplicitCastExpr from int.
> 
>     Following this path have you considered how to represent an int
>     parameter with value INT_MIN?
> 
>     I think there is no way you can represent it in standard conformant way
>     except to use -INT_MAX - 1 (i.e. -2147483647 <tel:2147483647> - 1 if
>     int has 32 bits).
> 
>     You cannot use -214783648 because no integer literal of type int with
>     value 214783648 can exists.
> 
>  
> Richard Smith brought up a similar point in the code review comments.  I
> am putting in an integer type selector which will move up to larger
> types until a large enough type can be found.  For instance, for
> int_min, use the negation of a long with a cast back to int.

What about when you don't have a larger type? (i.e. the minimum negative
number of larger signed integral type)