[LLVMbugs] [Bug 7792] New: ARM disassembler: rsb, rsc, pkh, ssat instructions emit zero shifts

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=7792

           Summary: ARM disassembler: rsb, rsc, pkh, ssat instructions
                    emit zero shifts
           Product: new-bugs
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: sliedes at cc.hut.fi
                CC: llvmbugs at cs.uiuc.edu


(trunk rev 110038)

Hi,

For most instructions, the disassembler does not output shifts where the amount
of the shift is zero. This is the behavior also recommended for ARM
disassemblers by the ARM Architecture Reference Manual.

However, for some instructions, a shift is emitted (this may not be a complete
list):

$ echo '0x01 0x00 0xf0 0x00' |Release+Asserts/bin/llvm-mc --disassemble
--triple=arm
        rsceqs  r0, r0, r1, lsl #0

$ echo '0x00 0x00 0x62 0x00' |Release+Asserts/bin/llvm-mc --disassemble
--triple=arm
        rsbeq   r0, r2, r0, lsl #0

$ echo '0x1b 0xf0 0x8b 0x96' |Release+Asserts/bin/llvm-mc --disassemble
--triple=arm
        pkhbtls pc, r11, r11, lsl #0

$ echo '0x1c 0x00 0xb0 0x46' |Release+Asserts/bin/llvm-mc --disassemble
--triple=arm
        ssatmi  r0, #17, r12, lsl #0

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