[Bug c/20355] New: MEM_READONLY_P & MEM_VOLATILE_P properties are lost on BLKmode rtl operands.

[schlie at comcast dot net]

It appears that some critical expression attributes are lost when memory reference expressions
are converted to rtl BLKmode operands typically used in (set BLK BLK) operations for example.

This bug prevents volatile and read-only BLKmode memory reference operands from being
treatedf properly as may be required, while these memory reference properties seem properly
retained in all other circimstances?

In particular the lost of this information assocaited with BLKmode mov-mem operands
inhibits the simple optional allocation of read-only data to program-rom, which may then
be properly identified by it's MEM_READONLY_P property, enabing specilized instructions to
to used to access it.

-- 
           Summary: MEM_READONLY_P & MEM_VOLATILE_P properties are lost on
                    BLKmode rtl operands.
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: schlie at comcast dot net
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: ppc-apple-darwin7.8
  GCC host triplet: ppc-apple-darwin7.8
GCC target triplet: avr-unknown-none


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20355