[LLVMbugs] [Bug 22852] New: Redundant mov generated for return value

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=22852

            Bug ID: 22852
           Summary: Redundant mov generated for return value
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: AArch64
          Assignee: unassignedbugs at nondot.org
          Reporter: james.molloy at arm.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

The following code:

unsigned long
baz (unsigned long a, unsigned long b)
{
  return (a & 0xffffffff) | (b & 0xffffffff00000000);
}

Produces:

baz:                                    // @baz
// BB#0:                                // %entry
    bfxil    x1, x0, #0, #32
    mov     x0, x1
    ret

The mov here is redundant; we can just emit "bfxil x0, x0, #0, #32".

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