Re: Q about Ada and value ranges in types

[kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)]

    I am tracking an ICE in VRP that triggers only in Ada.  Given
    this:

     1	D.1480_32 = nam_30 - 300000361;
     2	if (D.1480_32 <= 1) goto <L112>; else goto <L52>;
     3	<L112>:;
     4	D.1480_94 = ASSERT_EXPR <D.1480_32, D.1480_32 <= 1>;
     5	goto <bb 50> (<L57>);

    for name D.1480_94.  However, the type of D.1480 is:

    (gdb) ptu type
     const types__name_id___XDLU_300000000__399999999

     <integer_type 0xf6f3f360 types__name_id___XDLU_300000000__399999999
        type <integer_type 0xf6f3cec4 types__Tname_idB sizes-gimplified visited
    [ ... ]
         min <integer_cst 0xf6f40060 300000000>
        max <integer_cst 0xf6f40090 399999999>
         RM size <integer_cst 0xf6ee13f0 32>>

    My question is, is Ada emitting an always-false predicate in line
    #2?  Or is it a bug?

You're not showing where this comes from, so it's hard to say.  However
D.1480 is created by the gimplifier, not the Ada front end.  There could
easily be a typing problem in the tree there (e.g., that of the subtraction),
but I can't tell for sure.

    If the Ada language allows that kind of runtime check, then my
    fix to VRP will be different. 

I don't see it as a language issue: I'd argue that the tree in statement 2
is invalid given the typing.  That should be true for any language.

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