On 3/24/23 12:36, Jakub Jelinek wrote:
> On Fri, Mar 24, 2023 at 11:52:30AM -0400, Andrew MacLeod wrote:
>> Thanks.. Ive incorporated it into my commit  too.
> Note, both my earlier version of the patch and your patch regress:
> FAIL: gcc.dg/tree-ssa/vrp-float-3a.c scan-tree-dump-not evrp "link_error"
> FAIL: gcc.dg/tree-ssa/vrp-float-4a.c scan-tree-dump-not evrp "link_error"
>
> 	Jakub
>
OK, that was fun.

I commented in the PR, but the root issue is the way I was trying to 
communicate symbolic equivalence on operands to the compute_operand 
routines.

[1, 1 ]= a_1 != a_1

I was creating a relation record between op1 and op2 indicating they 
were equivalent.    THis record then gets passed up the gori call chain.

Reality is that this is not a true equivalence... without looking a the 
ranges, we dont know that that is true for general application, and and 
furthermore, when applied to something like a1 != a1, you can see the 
problem...

Once I corrected the value_relation record to create records with the 
same operand, things went south.

What we really need is to locally identify when op1 and op2 are the same 
symbol, and if there is no other information, pass it locally on that 
one statement  to the range-op handler.

Then, once we have processed the statement, we invoke the handler for 
that statement to cvreate a record which is passed up the chain.
so for:

     a_1 = b_4 + 1.0
     [1, 1] = (a_1 != a_1)

compute_operand_1 starts with no relation record, recognizes 
symbolically op1 and op2 are the same, and passes EQ_EXPR locally as the 
op1_op2 relation to the handler for NE_EXPR.   That handler utilizes the 
range of op2 to detemine whether != is true or not based on knowledge 
that op1 and op2 are the same value.     (for integer always false, for 
float, takes a look at NAN) and produces a result.

Before invoking compute_operand to calculate b_4 with the result of a_1,
   handler.op1_op2_relation (lhs);
is invoked to determine if there is a relation generated by the 
statement, which will generate  (a_1 != a_1), and pass that to compute 
operand for use in evaluating b_4.

Bootstraps on x86_64-pc-linux-gnu with no regressions.  OK for trunk?

Andrew