RE: [PATCH] Fix PR tree-optimization/77654

[Doug Gilmore <Doug dot Gilmore at imgtec dot com>]

> From: Richard Biener [rguenther@suse.de]
> Sent: Wednesday, September 21, 2016 12:48 AM
> To: Doug Gilmore
> Cc: gcc-patches@gcc.gnu.org; rguenth@gcc.gnu.org
> Subject: RE: [PATCH] Fix PR tree-optimization/77654
> 
> On Tue, 20 Sep 2016, Doug Gilmore wrote:
> 
> > It looks like the original message was dropped, resending.
> >
> > Doug
> > ________________________________________
> > From: Doug Gilmore
> > Sent: Tuesday, September 20, 2016 2:12 PM
> > To: gcc-patches@gcc.gnu.org; rguenth@gcc.gnu.org
> > Subject: [PATCH] Fix PR tree-optimization/77654
> >
> > From:
> >
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77654
> >
> > Richard Biener wrote:
> > > Looks good though addr_base should always be a pointer but it might
> > > not be an SSA name so better check that...
> >
> > I took a look at other situations where duplicate_ssa_name_ptr_info()
> > is called and found that there are no checks for the SSA name since
> > that check is done in duplicate_ssa_name_ptr_info().  Do you still
> > want the additional check added?
> 
> It checks for !ptr_info but it requires NAME to be an SSA name.
> 
> From the attachment in bugzilla (the attachment didn't make it
> here)
> 
> 
> +
> +      if (POINTER_TYPE_P (TREE_TYPE (addr_base)))
> +       {
> +         duplicate_ssa_name_ptr_info (addr, SSA_NAME_PTR_INFO (addr_base));
> +         /* As this isn't a plain copy we have to reset alignment
> +            information.  */
> +         if (SSA_NAME_PTR_INFO (addr))
> +           mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (addr));
> +       }
> +
> 
> I was talking about changing the if to
> 
>     if (TREE_CODE (addr_base) == SSA_NAME
>         && TREE_CODE (addr) == SSA_NAME)
Sorry I that missed point.  I glossed your comment "addr_base should
always be a pointer", causing me to go off into the weeds.

New patch attached.

Thanks,

Doug
> 
> because the addresses could be invariant as far as I can see.
> 
> > Also does it make sense to make a test case for this?
> 
> I'm not sure how to easily test this.
> 
> Richard.
> 
> ...

From 2d6cb0674ca66b4c5f6e335d73122e03413863e3 Mon Sep 17 00:00:00 2001
From: Doug Gilmore <doug.gilmore@imgtec.com>
Date: Tue, 6 Sep 2016 10:18:42 -0700
Subject: [PATCH] Ensure points-to information is maintained for prefetch.

gcc/
        PR tree-optimization/77654
        * tree-ssa-alias.c (issue_prefetch_ref): Add call
        to duplicate_ssa_name_ptr_info.
---
 gcc/tree-ssa-loop-prefetch.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/gcc/tree-ssa-loop-prefetch.c b/gcc/tree-ssa-loop-prefetch.c
index 26cf0a0..d0bd2d3 100644
--- a/gcc/tree-ssa-loop-prefetch.c
+++ b/gcc/tree-ssa-loop-prefetch.c
@@ -39,6 +39,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-ssa-loop-manip.h"
 #include "tree-ssa-loop-niter.h"
 #include "tree-ssa-loop.h"
+#include "ssa.h"
 #include "tree-into-ssa.h"
 #include "cfgloop.h"
 #include "tree-scalar-evolution.h"
@@ -1160,6 +1161,17 @@ issue_prefetch_ref (struct mem_ref *ref, unsigned unroll_factor, unsigned ahead)
           addr = force_gimple_operand_gsi (&bsi, unshare_expr (addr), true,
 					   NULL, true, GSI_SAME_STMT);
       }
+
+      if (TREE_CODE (addr_base) == SSA_NAME
+          && TREE_CODE (addr) == SSA_NAME)
+	{
+	  duplicate_ssa_name_ptr_info (addr, SSA_NAME_PTR_INFO (addr_base));
+	  /* As this isn't a plain copy we have to reset alignment
+	     information.  */
+	  if (SSA_NAME_PTR_INFO (addr))
+	    mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (addr));
+	}
+
       /* Create the prefetch instruction.  */
       prefetch = gimple_build_call (builtin_decl_explicit (BUILT_IN_PREFETCH),
 				    3, addr, write_p, local);
-- 
1.7.9.5