[Bug target/56315] New: ARM: Improve use of 64-bit constants in logical operations

[josh.m.conner at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56315

             Bug #: 56315
           Summary: ARM: Improve use of 64-bit constants in logical
                    operations
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: josh.m.conner@gmail.com


In the ARM backend, support was added for recognizing addition with 64-bit
constants that could be split up into two 32-bit literals that could be handled
with immediates in the adds/adc operations.  However, this support is still not
present for the logical operations.  For example, compiling this code with -O2:

  unsigned long long or64 (unsigned long long input)
  {
    return input | 0x200000004ULL;
  }

Gives us:

    mov    r2, #4
    mov    r3, #2
    orr    r0, r0, r2
    orr    r1, r1, r3

When it could produce:

    orr    r0, r0, #4
    orr    r1, r1, #2

The same improvement could be applied to & and ^ operations as well.