[PATCH] x86-64: don't allow use of %axl as accumulator

[H.J. Lu]

On Fri, Nov 10, 2017 at 4:50 AM, Jan Beulich <JBeulich@suse.com> wrote:
> Just like %cxl can't be used as shift count register. Otherwise for
> consistency %cxl would need to gain "ShiftCount" and use of both ought
> to properly cause REX prefixes to be emitted.

There are no good testcases for

axl, Reg8|Acc|Byte, RegRex64, 0, Dw2Inval, Dw2Inval
cxl, Reg8, RegRex64, 1, Dw2Inval, Dw2Inval
dxl, Reg8, RegRex64, 2, Dw2Inval, Dw2Inval
bxl, Reg8, RegRex64, 3, Dw2Inval, Dw2Inval
bpl, Reg8, RegRex64, 5, Dw2Inval, Dw2Inval

I am not sure if the whole thing is handled correctly.  If we want to change
them, we should make sure that they work correctly.

> gas/
> 2017-11-10  Jan Beulich  <jbeulich@suse.com>
>
>         * testsuite/gas/i386/x86-64-reg-bad.{s,l}: New.
>         * testsuite/gas/i386/i386.exp: Run new test.
>
> opcodes/
> 2017-11-10  Jan Beulich  <jbeulich@suse.com>
>
>         * i386-reg.tbl (axl): Remove Acc and Byte.
>         * i386-tbl.h: Re-generate.
>
> --- 2017-11-10/gas/testsuite/gas/i386/i386.exp
> +++ 2017-11-10/gas/testsuite/gas/i386/i386.exp
> @@ -628,6 +628,7 @@ if [expr ([istarget "i*86-*-*"] || [ista
>      run_dump_test "x86-64-mem"
>      run_dump_test "x86-64-mem-intel"
>      run_dump_test "x86-64-reg"
> +    run_list_test "x86-64-reg-bad" "-al"
>      run_dump_test "x86-64-reg-intel"
>      run_dump_test "x86-64-sib"
>      run_dump_test "x86-64-sib-intel"
> --- 2017-11-10/gas/testsuite/gas/i386/x86-64-reg-bad.l
> +++ 2017-11-10/gas/testsuite/gas/i386/x86-64-reg-bad.l
> @@ -0,0 +1,18 @@
> +.*: Assembler messages:
> +.*:4: Error: .* mismatch for `movabs'
> +.*:6: Error: .* mismatch for `div'
> +.*:7: Error: .* mismatch for `in'
> +.*:8: Error: .* mismatch for `lods'
> +.*:9: Error: .* mismatch for `shl'
> +GAS LISTING .*
> +
> +
> +[      ]*[1-9][0-9]*[  ]+\# Check %axl / %cxl aren't permitted as accumulator / shift count
> +[      ]*[1-9][0-9]*[  ]+\.text
> +[      ]*[1-9][0-9]*[  ]+reg:
> +[      ]*[1-9][0-9]*[  ]+movabs        -1, %axl
> +[      ]*[1-9][0-9]*[  ]+\?* 4080C001[         ]+add   \$1, %axl
> +[      ]*[1-9][0-9]*[  ]+div   %bl, %axl
> +[      ]*[1-9][0-9]*[  ]+in    %dx, %axl
> +[      ]*[1-9][0-9]*[  ]+lods  \(%rsi\), %axl
> +[      ]*[1-9][0-9]*[  ]+shl   %cxl, %eax
> --- 2017-11-10/gas/testsuite/gas/i386/x86-64-reg-bad.s
> +++ 2017-11-10/gas/testsuite/gas/i386/x86-64-reg-bad.s
> @@ -0,0 +1,9 @@
> +# Check %axl / %cxl aren't permitted as accumulator / shift count
> +       .text
> +reg:
> +       movabs  -1, %axl
> +       add     $1, %axl
> +       div     %bl, %axl
> +       in      %dx, %axl
> +       lods    (%rsi), %axl
> +       shl     %cxl, %eax
> --- 2017-11-10/opcodes/i386-reg.tbl
> +++ 2017-11-10/opcodes/i386-reg.tbl
> @@ -29,7 +29,7 @@ ah, Reg8, 0, 4, Dw2Inval, Dw2Inval
>  ch, Reg8, 0, 5, Dw2Inval, Dw2Inval
>  dh, Reg8, 0, 6, Dw2Inval, Dw2Inval
>  bh, Reg8, 0, 7, Dw2Inval, Dw2Inval
> -axl, Reg8|Acc|Byte, RegRex64, 0, Dw2Inval, Dw2Inval
> +axl, Reg8, RegRex64, 0, Dw2Inval, Dw2Inval
>  cxl, Reg8, RegRex64, 1, Dw2Inval, Dw2Inval
>  dxl, Reg8, RegRex64, 2, Dw2Inval, Dw2Inval
>  bxl, Reg8, RegRex64, 3, Dw2Inval, Dw2Inval
>
>



-- 
H.J.