[gcc r12-8195] tree-optimization/104010 - fix SLP scalar costing with patterns

[gcc r12-8195] tree-optimization/104010 - fix SLP scalar costing with patterns

[Richard Biener]

https://gcc.gnu.org/g:353434b65ef7972172597d232ae17022d9a57244

commit r12-8195-g353434b65ef7972172597d232ae17022d9a57244
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Apr 13 13:49:45 2022 +0200

    tree-optimization/104010 - fix SLP scalar costing with patterns
    
    When doing BB vectorization the scalar cost compute is derailed
    by patterns, causing lanes to be considered live and thus not
    costed on the scalar side.  For the testcase in PR104010 this
    prevents vectorization which was done by GCC 11.  PR103941
    shows similar cases of missed optimizations that are fixed by
    this patch.
    
    2022-04-13  Richard Biener  <rguenther@suse.de>
    
            PR tree-optimization/104010
            PR tree-optimization/103941
            * tree-vect-slp.cc (vect_bb_slp_scalar_cost): When
            we run into stmts in patterns continue walking those
            for uses outside of the vectorized region instead of
            marking the lane live.
    
            * gcc.target/i386/pr103941-1.c: New testcase.
            * gcc.target/i386/pr103941-2.c: Likewise.

Diff:
---
 gcc/testsuite/gcc.target/i386/pr103941-1.c | 14 +++++++++
 gcc/testsuite/gcc.target/i386/pr103941-2.c | 12 ++++++++
 gcc/tree-vect-slp.cc                       | 48 ++++++++++++++++++++++--------
 3 files changed, 62 insertions(+), 12 deletions(-)

diff --git a/gcc/testsuite/gcc.target/i386/pr103941-1.c b/gcc/testsuite/gcc.target/i386/pr103941-1.c
new file mode 100644
index 00000000000..524fdd0b4b1
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr103941-1.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse2" } */
+
+unsigned char ur[16], ua[16], ub[16];
+
+void avgu_v2qi (void)
+{
+  int i;
+
+  for (i = 0; i < 2; i++)
+    ur[i] = (ua[i] + ub[i] + 1) >> 1;
+}
+
+/* { dg-final { scan-assembler "pavgb" } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr103941-2.c b/gcc/testsuite/gcc.target/i386/pr103941-2.c
new file mode 100644
index 00000000000..972a32be997
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr103941-2.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse2" } */
+
+void foo (int *c, float *x, float *y)
+{
+  c[0] = x[0] < y[0];
+  c[1] = x[1] < y[1];
+  c[2] = x[2] < y[2];
+  c[3] = x[3] < y[3];
+}
+
+/* { dg-final { scan-assembler "cmpltps" } } */
diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index 4ac2b70303c..805dd7e10e2 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -5185,22 +5185,46 @@ vect_bb_slp_scalar_cost (vec_info *vinfo,
 	 the scalar cost.  */
       if (!STMT_VINFO_LIVE_P (stmt_info))
 	{
-	  FOR_EACH_PHI_OR_STMT_DEF (def_p, orig_stmt, op_iter, SSA_OP_DEF)
+	  auto_vec<gimple *, 8> worklist;
+	  hash_set<gimple *> *worklist_visited = NULL;
+	  worklist.quick_push (orig_stmt);
+	  do
 	    {
-	      imm_use_iterator use_iter;
-	      gimple *use_stmt;
-	      FOR_EACH_IMM_USE_STMT (use_stmt, use_iter, DEF_FROM_PTR (def_p))
-		if (!is_gimple_debug (use_stmt))
-		  {
-		    stmt_vec_info use_stmt_info = vinfo->lookup_stmt (use_stmt);
-		    if (!use_stmt_info
-			|| !vectorized_scalar_stmts.contains (use_stmt_info))
+	      gimple *work_stmt = worklist.pop ();
+	      FOR_EACH_PHI_OR_STMT_DEF (def_p, work_stmt, op_iter, SSA_OP_DEF)
+		{
+		  imm_use_iterator use_iter;
+		  gimple *use_stmt;
+		  FOR_EACH_IMM_USE_STMT (use_stmt, use_iter,
+					 DEF_FROM_PTR (def_p))
+		    if (!is_gimple_debug (use_stmt))
 		      {
-			(*life)[i] = true;
-			break;
+			stmt_vec_info use_stmt_info
+			  = vinfo->lookup_stmt (use_stmt);
+			if (!use_stmt_info
+			    || !vectorized_scalar_stmts.contains (use_stmt_info))
+			  {
+			    if (use_stmt_info
+				&& STMT_VINFO_IN_PATTERN_P (use_stmt_info))
+			      {
+				/* For stmts participating in patterns we have
+				   to check its uses recursively.  */
+				if (!worklist_visited)
+				  worklist_visited = new hash_set<gimple *> ();
+				if (!worklist_visited->add (use_stmt))
+				  worklist.safe_push (use_stmt);
+				continue;
+			      }
+			    (*life)[i] = true;
+			    goto next_lane;
+			  }
 		      }
-		  }
+		}
 	    }
+	  while (!worklist.is_empty ());
+next_lane:
+	  if (worklist_visited)
+	    delete worklist_visited;
 	  if ((*life)[i])
 	    continue;
 	}