From: Richard Biener <rguenther@suse.de>
Date: Mon, 30 Nov 2020 12:39:59 +0000 (+0100)
Subject: tree-optimization/98064 - fix BB SLP live lane extract wrt LC SSA
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=ebbe3f29518854c36574adbd4fa82fd56fa64056;p=gcc.git

tree-optimization/98064 - fix BB SLP live lane extract wrt LC SSA

This avoids breaking LC SSA when SLP codegen pulled an out-of-loop
def into a loop when merging with in-loop defs for an external def.

2020-11-30  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/98064
	* tree-vect-loop.c (vectorizable_live_operation): Avoid
	breaking LC SSA for BB vectorization.

	* g++.dg/vect/pr98064.cc: New testcase.
---

diff --git a/gcc/testsuite/g++.dg/vect/pr98064.cc b/gcc/testsuite/g++.dg/vect/pr98064.cc
new file mode 100644
index 00000000000..74043ce7725
--- /dev/null
+++ b/gcc/testsuite/g++.dg/vect/pr98064.cc
@@ -0,0 +1,25 @@
+// { dg-do compile }
+// { dg-additional-options "-O3" }
+
+const long long &min(const long long &__a, long long &__b) {
+  if (__b < __a)
+    return __b;
+  return __a;
+}
+extern long var_2;
+extern int var_3, var_8;
+extern long long var_5;
+extern unsigned short arr_353[];
+extern short arr_362[];
+extern int arr_518[];
+void test() {
+    for (char d = 0; d < 013; d += 4) {
+        for (char e = 0; e < 11; e++)
+            arr_353[e] = var_2 | min((long long)7, var_5);
+        for (int f = var_5; f; f += 4)
+            for (short g = var_8; g; g++)
+                arr_362[g] = 0;
+    }
+    for (short h = 5; (short)var_2; h += 5)
+        arr_518[h] = 0;
+}
diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index 48dfb4df00e..c8b4dc3a0c3 100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -8743,6 +8743,24 @@ vectorizable_live_operation (vec_info *vinfo,
 				   "def\n");
 		continue;
 	      }
+	    /* ???  It can also happen that we end up pulling a def into
+	       a loop where replacing out-of-loop uses would require
+	       a new LC SSA PHI node.  Retain the original scalar in
+	       those cases as well.  PR98064.  */
+	    if (TREE_CODE (new_tree) == SSA_NAME
+		&& !SSA_NAME_IS_DEFAULT_DEF (new_tree)
+		&& (gimple_bb (use_stmt)->loop_father
+		    != gimple_bb (vec_stmt)->loop_father)
+		&& !flow_loop_nested_p (gimple_bb (vec_stmt)->loop_father,
+					gimple_bb (use_stmt)->loop_father))
+	      {
+		if (dump_enabled_p ())
+		  dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+				   "Using original scalar computation for "
+				   "live lane because there is an out-of-loop "
+				   "definition for it\n");
+		continue;
+	      }
 	    FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
 	      SET_USE (use_p, new_tree);
 	    update_stmt (use_stmt);