middle-end/5100: Wrong register class selected by find_valid_class

[maltieri@nergal.it]

>Number:         5100
>Category:       middle-end
>Synopsis:       Wrong register class selected by find_valid_class
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Dec 13 02:36:00 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     Marco Altieri
>Release:        3.0
>Organization:
>Environment:
Linux 7.0.
>Description:
We are devoloping a porting of gcc to a new DSP architecture
that has pointers whith a size of 2 registers.
A pointer must always be allocated on a even/odd pair
of registers.
HARD_REGNO_MODE_OK macro returns 0 for all the odd
registers when the mode is Pmode.
There are classes for even registers (EVEN_REGS), odd
registers (ODD_REGS) and all the general registers
(GENERAL_REGS).
The algorithm used by find_valid_class rejects
GENERAL_REGS class for a Pmode subreg and returns
EVEN_REGS.
This is incorrect because a double-sized mode can not
be allocated in EVEN_REGS class.
>How-To-Repeat:

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: