wi::max_value() of a boolean is not 1

Aldy Hernandez aldyh@redhat.com
Sun Aug 20 10:40:00 GMT 2017


Hi folks.

Calling wi::max_value() of a boolean_type creates a wide_int with all 
bits set, not just the least significant bit.

tree type = boolean_type_node;
wide_int x = wi::max_value (TYPE_PRECISION (type), TYPE_SIGN (type));
(gdb) print x.dump()
[0xffffffffffffffff], precision = 1

However, one can also create a boolean of true with:

wide_int one = wi::uhwi (1, TYPE_PRECISION (boolean_type_node));
(gdb) print one.dump()
[0x1], precision = 1

These will not be equal to each other because wi::eq_p() will only strip 
off excess bits when <is_sign_extended=false>.  However, 
is_sign_extended=true for all wide_int's.

Am I doing something wrong?

Could I change wi::max_value() to strip off excess bits, instead of 
setting all bits like it's currently doing:

wide_int
wi::max_value (unsigned int precision, signop sgn)
{
   gcc_checking_assert (precision != 0);
   if (sgn == UNSIGNED)
     /* The unsigned max is just all ones.  */
     return shwi (-1, precision);
...
...

Or perhaps change wi::eq_p() to strip off excess bits?

Or am I missing something else entirely?
Aldy



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