[LLVMbugs] [Bug 12519] New: llc produce wrong assembly for ARM on following .ll code

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Tue Apr 10 07:38:07 PDT 2012


             Bug #: 12519
           Summary: llc produce wrong assembly for ARM on following .ll
           Product: new-bugs
           Version: 3.0
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: babslachem at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 8368
  --> http://llvm.org/bugs/attachment.cgi?id=8368
ll file to reproduce problem

On attached .ll file when compiled with llc 3.0 as follows:

llc vabug.ll -march=arm -mcpu=cortex-a9 -mattr=+neon,+neonfp
-relocation-model=pic -o vabug.s

llc produce following ARM code:

    ldr r0, [sp, #4]
    add r1, r0, #4
    str r1, [sp, #4]
    ldrb    r1, [r0], #11
    and r0, r0, #248              # BUG HERE ?
    add r2, r0, #16
    str r1, [sp, #96]
    str r2, [sp, #4]
    vldr.64 d16, [r0]
    mov r0, r4
    vcvt.s32.f64    s0, d16
    vstr.32 s0, [sp, #100]
    bl  check(PLT)

I think line marked as 'BUG HERE' is incorrect. I'm expecting llc to generate
    bfc r0, #0, #3

Correct code is generated when I change 'zext' by 'sext' in LLVM code line #31,
which to me doesn't make sense.

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