Re: [PATCH] Make sure SCALAR_INT_MODE_P before invoke try_const_anchors

[Richard Biener <rguenther@suse.de>]

On Fri, 9 Jun 2023, Jiufu Guo wrote:

> Hi,
> 
> As checking the code, there is a "gcc_assert (SCALAR_INT_MODE_P (mode))"
> in "try_const_anchors".
> This assert seems correct because the function try_const_anchors cares
> about integer values currently, and modes other than SCALAR_INT_MODE_P
> are not needed to support.
> 
> This patch makes sure SCALAR_INT_MODE_P when calling try_const_anchors.
> 
> This patch is raised when drafting below one.
> https://gcc.gnu.org/pipermail/gcc-patches/2022-October/603530.html.
> With that patch, "{[%1:DI]=0;} stack_tie" with BLKmode runs into
> try_const_anchors, and hits the assert/ice.
> 
> Boostrap and regtest pass on ppc64{,le} and x86_64.
> Is this ok for trunk?

Iff the correct fix at all (how can a CONST_INT have BLKmode?) then
I suggest to instead fix try_const_anchors to change

  /* CONST_INT is used for CC modes, but we should leave those alone.  */
  if (GET_MODE_CLASS (mode) == MODE_CC)
    return NULL_RTX;

  gcc_assert (SCALAR_INT_MODE_P (mode));

to

  /* CONST_INT is used for CC modes, leave any non-scalar-int mode alone.  */
  if (!SCALAR_INT_MODE_P (mode))
    return NULL_RTX;

but as said I wonder how we arrive at a BLKmode CONST_INT and whether
we should have fended this off earlier.  Can you share more complete
RTL of that stack_tie?

> 
> BR,
> Jeff (Jiufu Guo)
> 
> gcc/ChangeLog:
> 
> 	* cse.cc (cse_insn): Add SCALAR_INT_MODE_P condition.
> 
> ---
>  gcc/cse.cc | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/gcc/cse.cc b/gcc/cse.cc
> index 2bb63ac4105..f213fa0faf7 100644
> *** a/gcc/cse.cc
> --- b/gcc/cse.cc
> ***************
> *** 5003,5009 ****
>         if (targetm.const_anchor
>   	  && !src_related
>   	  && src_const
> ! 	  && GET_CODE (src_const) == CONST_INT)
>   	{
>   	  src_related = try_const_anchors (src_const, mode);
>   	  src_related_is_const_anchor = src_related != NULL_RTX;
> - - 
> --- 5003,5010 ----
>         if (targetm.const_anchor
>   	  && !src_related
>   	  && src_const
> ! 	  && GET_CODE (src_const) == CONST_INT
> ! 	  && SCALAR_INT_MODE_P (mode))
>   	{
>   	  src_related = try_const_anchors (src_const, mode);
>   	  src_related_is_const_anchor = src_related != NULL_RTX;
> 2.39.3
> 
> 

-- 
Richard Biener <rguenther@suse.de>
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