Re: [Patch] Teach genrecog/genoutput that scratch registers require write constraint modifiers

[Jeff Law <law at redhat dot com>]

On 09/18/14 04:19, James Greenhalgh wrote:
> Hi,
>
> As discussed in https://gcc.gnu.org/ml/gcc-patches/2014-09/msg01334.html
> The construct
>
>    (clobber (match_scratch 0 "r"))
>
> is invalid - operand 0 must be marked either write or read/write.
>
> Likewise
>
>    (match_* 0 "&r")
>
> is invalid, marking an operand earlyclobber does not remove the need to
> also mark it write or read/write.
>
> This patch adds checking for these two error conditions to the generator
> programs and documents the restriction.
>
> Bootstrapped on x86, ARM and AArch64 with no new issues.
>
> Ok?
>
> Thanks,
> James
>
> ---
> 2014-09-17  James Greenhalgh  <james.greenhalgh@arm.com>
>
> 	* doc/md.texi (Modifiers): Consistently use "read/write"
> 	nomenclature rather than "input/output".
> 	* genrecog.c (constraints_supported_in_insn_p): New.
> 	(validate_pattern): If needed, also check constraints on
> 	MATCH_SCRATCH operands.
> 	* genoutput.c (validate_insn_alternatives): Catch earlyclobber
> 	operands with no '=' or '+' modifier.

+	    if (c == '=' || c == '+')
+	      seen_inout = true;

Isn't "seen_input" poorly named here?  ISTM what we're checking for is 
if we've seen an operand that will be written to.

Doesn't it make sense to use read/write nomenclature in the comments and 
variable names too?

So with those nits fixed, this patch is OK.

Jeff