From 38ead98b2fe49b1fef4ae7c9771af48be7adaa10 Mon Sep 17 00:00:00 2001
From: Ju-Zhe Zhong <juzhe.zhong@rivai.ai>
Date: Mon, 26 Jun 2023 15:43:42 +0800
Subject: [PATCH] DSE: Add LEN_MASK_STORE analysis into DSE and fix LEN_STORE

Hi, Richi.

This patch is adding LEN_MASK_STORE into DSE.

My understanding is LEN_MASK_STORE is predicated by mask and len.
No matter len is constant or not, the ao_ref should be the same as MASK_STORE.

Wheras for LEN_STORE, when len is constant, we use (len - bias), otherwise, it's
the same as MASK_STORE/LEN_MASK_STORE.

Not sure whether I am on the same page with you, feel free to correct me.

Thanks.

gcc/ChangeLog:

	* tree-ssa-dse.cc (initialize_ao_ref_for_dse): Add LEN_MASK_STORE and
	fix LEN_STORE.
	(dse_optimize_stmt): Add LEN_MASK_STORE.
---
 gcc/tree-ssa-dse.cc | 47 ++++++++++++++++++++++++++++++---------------
 1 file changed, 31 insertions(+), 16 deletions(-)

diff --git a/gcc/tree-ssa-dse.cc b/gcc/tree-ssa-dse.cc
index 3c7a2e9992d..f8338037a61 100644
--- a/gcc/tree-ssa-dse.cc
+++ b/gcc/tree-ssa-dse.cc
@@ -48,6 +48,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-ssa-loop-niter.h"
 #include "cfgloop.h"
 #include "tree-data-ref.h"
+#include "internal-fn.h"
 
 /* This file implements dead store elimination.
 
@@ -157,23 +158,36 @@ initialize_ao_ref_for_dse (gimple *stmt, ao_ref *write, bool may_def_ok = false)
       switch (gimple_call_internal_fn (stmt))
 	{
 	case IFN_LEN_STORE:
-	  ao_ref_init_from_ptr_and_size
-	      (write, gimple_call_arg (stmt, 0),
-	       int_const_binop (MINUS_EXPR,
-				gimple_call_arg (stmt, 2),
-				gimple_call_arg (stmt, 4)));
-	  return true;
 	case IFN_MASK_STORE:
-	  /* We cannot initialize a must-def ao_ref (in all cases) but we
-	     can provide a may-def variant.  */
-	  if (may_def_ok)
-	    {
-	      ao_ref_init_from_ptr_and_size
-		  (write, gimple_call_arg (stmt, 0),
-		   TYPE_SIZE_UNIT (TREE_TYPE (gimple_call_arg (stmt, 3))));
-	      return true;
-	    }
-	  break;
+	case IFN_LEN_MASK_STORE:
+	  {
+	    int stored_value_index
+	      = internal_fn_stored_value_index (gimple_call_internal_fn (stmt));
+	    if (gimple_call_internal_fn (stmt) == IFN_LEN_STORE)
+	      {
+		tree len = gimple_call_arg (stmt, 2);
+		tree bias = gimple_call_arg (stmt, 4);
+		if (tree_fits_uhwi_p (len))
+		  {
+		    ao_ref_init_from_ptr_and_size (write,
+						   gimple_call_arg (stmt, 0),
+						   int_const_binop (MINUS_EXPR,
+								    len, bias));
+		    return true;
+		  }
+	      }
+	    /* We cannot initialize a must-def ao_ref (in all cases) but we
+	       can provide a may-def variant.  */
+	    if (may_def_ok)
+	      {
+		ao_ref_init_from_ptr_and_size (
+		  write, gimple_call_arg (stmt, 0),
+		  TYPE_SIZE_UNIT (
+		    TREE_TYPE (gimple_call_arg (stmt, stored_value_index))));
+		return true;
+	      }
+	    break;
+	  }
 	default:;
 	}
     }
@@ -1502,6 +1516,7 @@ dse_optimize_stmt (function *fun, gimple_stmt_iterator *gsi, sbitmap live_bytes)
 	{
 	case IFN_LEN_STORE:
 	case IFN_MASK_STORE:
+	case IFN_LEN_MASK_STORE:
 	  {
 	    enum dse_store_status store_status;
 	    store_status = dse_classify_store (&ref, stmt, false, live_bytes);