[LLVMbugs] [Bug 13036] New: Thumb FSTMX/FLDMX instructions are not supported

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13036

             Bug #: 13036
           Summary: Thumb FSTMX/FLDMX instructions are not supported
           Product: libraries
           Version: trunk
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: ARM
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: richard.barton at arm.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


The Thumb backend does not support the FLDMX/FSTMX instructions.

These instructions are a bit of a curiosity in that they are pre-ARMv6 (VFPv1)
instruction mnemonics which were not superseded by UAL-style V* mnemonics. They
still exist in VFPv4 (ARMv7) but their use is deprecated. Any VSTM/VLDM's with
odd numbered 'imm8' fields (bottom 8 bits) are the old-style F* encodings, and
the encoding for the immediate is different.

Reproduce with:  echo 0x80 0xec 0x03 0x0b |
/work/ricbar01/llvm-oss/build/bin/llvm-mc -triple thumbv7 -show-inst
-show-encoding -disassemble

        .section        __TEXT,__text,regular,pure_instructions
        vstmia  r0, {d0}                @ encoding: [0x80,0xec,0x02,0x0b]
                                        @ <MCInst #2086 VSTMDIA
                                        @  <MCOperand Reg:60>
                                        @  <MCOperand Imm:14>
                                        @  <MCOperand Reg:0>
                                        @  <MCOperand Reg:3>>

These instructions are completely unsupported, so the symptoms are not always
to decode a VSTM. e.g.

echo 0x80 0xec 0x01 0x0b | /work/ricbar01/llvm-oss/build/bin/llvm-mc -triple
thumbv7 -show-inst -show-encoding -disassemble

        .section        __TEXT,__text,regular,pure_instructions
<stdin>:1:1: warning: invalid instruction encoding
0x80 0xec 0x01 0x0b
^
        lsls    r4, r5, #7              @ encoding: [0xec,0x01]
                                        @ <MCInst #2644 tLSLri
                                        @  <MCOperand Reg:64>
                                        @  <MCOperand Reg:2>
                                        @  <MCOperand Reg:65>
                                        @  <MCOperand Imm:7>
                                        @  <MCOperand Imm:14>
                                        @  <MCOperand Reg:0>>
<stdin>:1:16: warning: invalid instruction encoding
0x80 0xec 0x01 0x0b
               ^

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