[Bug target/77729] New: aarch64 inserts unneeded uxtb after ldrb, orr ...32

[jak@jak-linux.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77729

            Bug ID: 77729
           Summary: aarch64 inserts unneeded uxtb after ldrb, orr ...32
           Product: gcc
           Version: 6.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jak@jak-linux.org
  Target Milestone: ---

In the attached test case, the aarch64 target inserts a uxtb instruction that
is not needed:

        ldrb    w1, [x0]
        orr     w1, w1, 32
        uxtb    w1, w1
        cmp     w1, 116

The arm backend handles that just fine:

        ldrb    r3, [r0]        @ zero_extendqisi2
        orr     r3, r3, #32
        cmp     r3, #116

It also works with 33 or 34 instead of 32 for whatever reasons.