[LLVMbugs] [Bug 7433] New: Invalid code generated with arm-tail-calls

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sun Jun 20 23:48:22 PDT 2010


           Summary: Invalid code generated with arm-tail-calls
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: ARM
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: rafael.espindola at gmail.com
                CC: llvmbugs at cs.uiuc.edu

With arm-tail-calls enabled the attached testcase is miscompiled. The diff of
the output shows what the problem is:

$ diff test-ok.s  test-nok.s 
<     mov    lr, pc
<     bx    r7
<     ldmia    sp!, {r4, r5, r6, r7, r8, pc}
> 	ldmia	sp!, {r4, r5, r6, r7, r8, lr}
> 	bx	r7  @ TAILCALL

The code is setting r7 back before branching to it. The tail call opt should be
copying the value into a caller save register.

To reproduce:

$ llc test.ll -o test-ok.s  --arm-tail-calls=false
$ llc test.ll -o test-nok.s

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