Re: [PATCH] tcg/s390: Fix compare instruction from extended-immediate facility

[Richard W.M. Jones]

On Thu, Feb 04, 2021 at 07:29:02PM +0100, Philippe Mathieu-Daudé wrote:
> The code is currently comparing c2 to the type promotion of
> uint32_t and int32_t. That is, the conversion rules are as:
> 
>   (common_type) c2 == (common_type) (uint32_t)
>                         (is_unsigned
>                         ? (uint32_t)c2
>                         : (uint32_t)(int32_t)c2)
> 
> In the signed case we lose the desired sign extensions because
> of the argument promotion rules of the ternary operator.
> 
> Solve the problem by doing the round-trip parsing through the
> intermediate type and back to the desired common type (all at
> one expression).
> 
> Fixes: a534bb15f30 ("tcg/s390: Use constant pool for cmpi")
> Reported-by: Miroslav Rezanina <mrezanin@redhat.com>
> Reported-by: Richard W.M. Jones <rjones@redhat.com>
> Suggested-by: David Hildenbrand <david@redhat.com>
> Suggested-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  tcg/s390/tcg-target.c.inc | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tcg/s390/tcg-target.c.inc b/tcg/s390/tcg-target.c.inc
> index b67470137c4..695d7ee6523 100644
> --- a/tcg/s390/tcg-target.c.inc
> +++ b/tcg/s390/tcg-target.c.inc
> @@ -1067,7 +1067,7 @@ static int tgen_cmp(TCGContext *s, TCGType type, 
> TCGCond c, TCGReg r1,
>                  op = (is_unsigned ? RIL_CLFI : RIL_CFI);
>                  tcg_out_insn_RIL(s, op, r1, c2);
>                  goto exit;
> -            } else if (c2 == (is_unsigned ? (uint32_t)c2 : (int32_t)c2)) {
> +            } else if (c2 == (is_unsigned ? (TCGArg)(uint32_t)c2 : 
> (TCGArg)(int32_t)c2)) {
>                  op = (is_unsigned ? RIL_CLGFI : RIL_CGFI);
>                  tcg_out_insn_RIL(s, op, r1, c2);
>                  goto exit;

I have tested this patch on an s390x host on top of 1ed9228f63e "Merge
remote-tracking branch 'remotes/ericb/tags/pull-nbd-2021-02-02-v2'
into staging" and I can confirm that it fixes both previously reported
problems.  Therefore you can add:

Tested-by: Richard W.M. Jones <rjones@redhat.com>

Rich.

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