Re: [Patch][gas][arm] Diagnose unpredictable mrrc, mrrc2 etc instructions

["Richard Earnshaw (lists)" <Richard dot Earnshaw at arm dot com>]

On 16/08/16 14:25, Tamar Christina wrote:
> Hi All,
> 
> When instructions such as MRRC are used with the same destination registers
> then the result is unpredictable but no warning was issued to the user.
> 
> This patch adds a warning for this pattern to the instructions:
> 
> * MRRC
> * MRRC2
> 
> 
> Added new test for message and ran tests for gas for arm-none-linux-gnueabi:
> 
> Ok for trunk?
> 
> Thanks,
> Tamar
> 
> gas/
> 2016-08-09  Tamar Christina  <tamar.christina@arm.com>
> 
> 	* config/tc-arm.c (do_co_reg2c): Added constraint.
> 
> gas/testsuite/
> 2016-08-09  Tamar Christina  <tamar.christina@arm.com>
> 
> 	* gas/arm/dest-unpredictable.s: New.
> 	* gas/arm/dest-unpredictable.l: New.
> 	* gas/arm/dest-unpredictable.d: New.
> 
> 
> binutils_review6.patch
> 
> 
> :100644 100644 73d0531... 9d0aeae... M	gas/config/tc-arm.c
> :000000 100644 0000000... 129d08c... A	gas/testsuite/gas/arm/dest-unpredictable.d
> :000000 100644 0000000... 7c17c25... A	gas/testsuite/gas/arm/dest-unpredictable.l
> :000000 100644 0000000... fae22be... A	gas/testsuite/gas/arm/dest-unpredictable.s
> 
> diff --git a/gas/config/tc-arm.c b/gas/config/tc-arm.c
> index 73d0531..9d0aeae 100644
> --- a/gas/config/tc-arm.c
> +++ b/gas/config/tc-arm.c
> @@ -8691,6 +8691,14 @@ do_co_reg2c (void)
>        constraint (Rn == REG_PC, BAD_PC);
>      }
>  
> +  /* Only check the MRRC{2} variants.  */
> +  if ((inst.instruction & 0x0C500000) == 0x0C500000)

I think the mask should be 0x0CF00000 - you do care that bits 21 and 23
are both zero.

OK with that change.

R.

> +    {
> +       /* If Rd == Rn, error that the operation is
> +	  unpredictable (example MRRC p3,#1,r1,r1,c4).  */
> +       constraint (Rd == Rn, BAD_OVERLAP);
> +    }
> +
>    inst.instruction |= inst.operands[0].reg << 8;
>    inst.instruction |= inst.operands[1].imm << 4;
>    inst.instruction |= Rd << 12;
> diff --git a/gas/testsuite/gas/arm/dest-unpredictable.d b/gas/testsuite/gas/arm/dest-unpredictable.d
> new file mode 100644
> index 0000000..129d08c
> --- /dev/null
> +++ b/gas/testsuite/gas/arm/dest-unpredictable.d
> @@ -0,0 +1,2 @@
> +# name: Unpredictable MRRC and MRRC2 instructions. - ARM
> +# error-output: dest-unpredictable.l
> diff --git a/gas/testsuite/gas/arm/dest-unpredictable.l b/gas/testsuite/gas/arm/dest-unpredictable.l
> new file mode 100644
> index 0000000..7c17c25
> --- /dev/null
> +++ b/gas/testsuite/gas/arm/dest-unpredictable.l
> @@ -0,0 +1,5 @@
> +[^:]*: Assembler messages:
> +[^:]*:6: Error: registers may not be the same -- `mrrc p0,#1,r1,r1,c4'
> +[^:]*:7: Error: registers may not be the same -- `mrrc2 p0,#1,r1,r1,c4'
> +[^:]*:20: Error: registers may not be the same -- `mrrc p0,#1,r1,r1,c4'
> +[^:]*:21: Error: registers may not be the same -- `mrrc2 p0,#1,r1,r1,c4'
> diff --git a/gas/testsuite/gas/arm/dest-unpredictable.s b/gas/testsuite/gas/arm/dest-unpredictable.s
> new file mode 100644
> index 0000000..fae22be
> --- /dev/null
> +++ b/gas/testsuite/gas/arm/dest-unpredictable.s
> @@ -0,0 +1,29 @@
> +.syntax unified
> +
> +.arm
> +
> +@ warnings
> +mrrc  p0,#1,r1,r1,c4		@ unpredictable
> +mrrc2 p0,#1,r1,r1,c4		@ ditto
> +
> +@ normal
> +mrrc  p0,#1,r1,r2,c4		@ predictable
> +mrrc2 p0,#1,r1,r2,c4		@ ditto
> +mcrr  p0,#1,r1,r2,c4		@ ditto
> +mcrr2 p0,#1,r1,r2,c4		@ ditto
> +mcrr  p0,#1,r1,r1,c4		@ ditto
> +mcrr2 p0,#1,r1,r1,c4		@ ditto
> +
> +.thumb
> +
> +@ warnings
> +mrrc  p0,#1,r1,r1,c4		@ unpredictable
> +mrrc2 p0,#1,r1,r1,c4		@ ditto
> +
> +@ normal
> +mrrc  p0,#1,r1,r2,c4		@ predictable
> +mrrc2 p0,#1,r1,r2,c4		@ ditto
> +mcrr  p0,#1,r1,r2,c4		@ ditto
> +mcrr2 p0,#1,r1,r2,c4		@ ditto
> +mcrr  p0,#1,r1,r1,c4		@ ditto
> +mcrr2 p0,#1,r1,r1,c4		@ ditto
>