[LLVMbugs] [Bug 21742] New: PowerPC cc clobber fails to clobber cr0

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Wed Dec 3 21:26:00 PST 2014


            Bug ID: 21742
           Summary: PowerPC cc clobber fails to clobber cr0
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: PowerPC
          Assignee: unassignedbugs at nondot.org
          Reporter: anton at samba.org
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

I'm testing with a build that contains r223328. I notice at least one place
where using "cc" in the clobbers doesn't actually clobber cr0. We see the
andi./iselgt broken up by some inline assembly:

    12f0:       01 00 84 70     andi.   r4,r4,1
    12f4:       a8 18 80 7c     ldarx   r4,0,r3
    12f8:       78 a0 84 7c     andc    r4,r4,r20
    12fc:       ad 19 80 7c     stdcx.  r4,0,r3
    1300:       f4 ff a2 40     bne     12f4
    1304:       5e c8 b5 7e     iselgt  r21,r21,r25

If I convert the inline assembly to use "cr0", then we see the correct

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