[Bug rtl-optimization/35044] New: resource.c:find_dead_or_set_registers doesn't grok COND_EXEC

[amylaar at gcc dot gnu dot org]

find_dead_or_set_registers uses mark_set_resources to determine if a register
is set, and if it is, it concludes that the register is before that set.
A register is also considered set when the set is inside a COND_EXEC, thus
delay slot scheduling can clobber values in registers that are supposed
to remain untouched when a COND_EXEC is not executed.

I have a patch for this, which changes find_dead_or_set_registers to not call
mark_set_resources for COND_EXEC patterns when the purpose is to find registers
that are killed.
I can't post this patch, or the target port we are using, at the moment
since we don't have a copyright assignment on file yet.

Another approach would be to change mark_set_resources to take a parameter
to tell it if the conservative assumption is that the register is set or
if it that the register is not set, and change all callers to provide an
appropriate value.


-- 
           Summary: resource.c:find_dead_or_set_registers doesn't grok
                    COND_EXEC
           Product: gcc
           Version: 4.2.1
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: amylaar at gcc dot gnu dot org
GCC target triplet: arc-elf32


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35044