[tree-ssa] where to fix this?

[Dale Johannesen]

On Dec 19, 2003, at 8:17 AM, law@redhat.com wrote:
> In message <978715DA-31C9-11D8-B11A-000A95D7CD40@apple.com>, Dale 
> Johannesen wr
> ites:
>> I have a case where tree-ssa is calling fold() on this:
>>
>> <plus_expr 0x9c80a0
>>     type <integer_type 0x40d42528 int SI
>>         size <integer_cst 0x8e4780 constant invariant 32>
>>         unit size <integer_cst 0x8e4798 constant invariant 4>...
>>     invariant
>>     arg 0 <integer_cst 0x40d40570 type <boolean_type 0x40d427f8 _Bool>
>> constant invariant 1>
>>     arg 1 <integer_cst 0x97eed0 type <integer_type 0x40d42528 int>
>> constant invariant 1>>
>>
>> which gets into int_const_binop, which thinks the result is _Bool and
>> truncates it to 0.
>> Not what we want.  Would the preference be to fix this in fold(), or
>> make tree_ssa
>> produce trees that incorporate the C promotions?
> We'd need more context to know what's happening.   testcases help a 
> lot :-)

I'm not asking anybody to fix the bug, I will do that, I just want to 
know what the
defined semantics of fold() are.  Is is supposed to handle the tree 
above or not?

This arises from perlbmk in SPEC compiled -O3.  It hangs at runtime and 
I'm surprised
nobody else has seen it.  The original code was

   x = (p !=0) + (q!=0)

and after a few rounds of optimization it transforms into the above.
I haven't tried to construct a small test yet, but it should certainly 
be possible.