[Bug c/43128] [4.5 Regression] c-c++-common/pr41779.c doesn't work

[joseph at codesourcery dot com]

------- Comment #19 from joseph at codesourcery dot com  2010-02-23 00:29 -------
Subject: Re:  [4.5 Regression] c-c++-common/pr41779.c doesn't
 work

On Mon, 22 Feb 2010, manu at gcc dot gnu dot org wrote:

> ------- Comment #18 from manu at gcc dot gnu dot org  2010-02-22 23:56 -------
> (In reply to comment #17)
> > suggest having a c_ep_convert_and_check or similar function that handles 
> > excess precision: it would take the result type, the semantic result type 
> > (the type that gets used eventually to build an EXCESS_PRECISION_EXPR) and 
> > the value to convert.  It would just call convert_and_check, ignoring the 
> > semantic type, *except* when the operand has integer type *and* the 
> > semantic type is non-NULL; in that case, it would first convert to the 
> > semantic type them to the result type.
> 
> Wouldn't that change the normal result of promotion rules?

No.

The present logic is: convert (with convert_and_check) both operands to a 
common type, which may have excess precision; then, later, after producing 
the tree for the result of the operation, wrap that in an 
EXCESS_PRECISION_EXPR, using the semantic type, if there is a semantic 
type different from the type with excess precision.

The proposed logic is the same, *except* that the conversion to a common 
type goes via the semantic type, *if* there is excess precision involved 
*and* the operand being converted had integer type.

> Also, why call convert_and_check ignoring the semantic type and not just call
> convert? The excess precision type should be large enough to not cause any
> problem that needs checking.

Yes, you could just use convert for the second conversion (semantic type 
to type with excess precision).


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43128