diff mbox series

tree-optimization/99253 - fix reduction path check

Message ID nycvar.YFH.7.76.2102251028300.20162@elmra.sevgm.obk
State New
Headers show
Series tree-optimization/99253 - fix reduction path check | expand

Commit Message

Richard Biener Feb. 25, 2021, 9:28 a.m. UTC 
This fixes an ordering problem with verifying that no intermediate
computations in a reduction path are used outside of the chain.  The
check was disabled for value-preserving conversions at the tail
but whether a stmt was a conversion or not was only computed after
the first use.  The following fixes this by re-ordering things
accordingly.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

2021-02-25  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/99253
	* tree-vect-loop.c (check_reduction_path): First compute
	code, then verify out-of-loop uses.

	* gcc.dg/vect/pr99253.c: New testcase.
---
 gcc/testsuite/gcc.dg/vect/pr99253.c | 22 ++++++++++++
 gcc/tree-vect-loop.c                | 56 ++++++++++++++---------------
 2 files changed, 50 insertions(+), 28 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/vect/pr99253.c
diff mbox series

Patch

diff --git a/gcc/testsuite/gcc.dg/vect/pr99253.c b/gcc/testsuite/gcc.dg/vect/pr99253.c
new file mode 100644
index 00000000000..9e3345025ba
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr99253.c
@@ -0,0 +1,22 @@ 
+/* { dg-do run } */
+
+#include "tree-vect.h"
+
+int a = 0;
+static int b = 0;
+long c = 0;
+
+int
+main()
+{
+  check_vect ();
+  for (int d = 0; d < 8; d++)
+    {
+      a ^= c;
+      b = a;
+      a ^= 1;
+    }
+  if (a != 0 || b != 1)
+    __builtin_abort();
+  return 0;
+}
diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index 27845c01430..3e973e774af 100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -3432,34 +3432,6 @@  pop:
 	  fail = true;
 	  break;
 	}
-      /* Check there's only a single stmt the op is used on.  For the
-	 not value-changing tail and the last stmt allow out-of-loop uses.
-	 ???  We could relax this and handle arbitrary live stmts by
-	 forcing a scalar epilogue for example.  */
-      imm_use_iterator imm_iter;
-      gimple *op_use_stmt;
-      unsigned cnt = 0;
-      FOR_EACH_IMM_USE_STMT (op_use_stmt, imm_iter, op)
-	if (!is_gimple_debug (op_use_stmt)
-	    && (*code != ERROR_MARK
-		|| flow_bb_inside_loop_p (loop, gimple_bb (op_use_stmt))))
-	  {
-	    /* We want to allow x + x but not x < 1 ? x : 2.  */
-	    if (is_gimple_assign (op_use_stmt)
-		&& gimple_assign_rhs_code (op_use_stmt) == COND_EXPR)
-	      {
-		use_operand_p use_p;
-		FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
-		  cnt++;
-	      }
-	    else
-	      cnt++;
-	  }
-      if (cnt != 1)
-	{
-	  fail = true;
-	  break;
-	}
       tree_code use_code = gimple_assign_rhs_code (use_stmt);
       if (use_code == MINUS_EXPR)
 	{
@@ -3489,6 +3461,34 @@  pop:
 	  fail = true;
 	  break;
 	}
+      /* Check there's only a single stmt the op is used on.  For the
+	 not value-changing tail and the last stmt allow out-of-loop uses.
+	 ???  We could relax this and handle arbitrary live stmts by
+	 forcing a scalar epilogue for example.  */
+      imm_use_iterator imm_iter;
+      gimple *op_use_stmt;
+      unsigned cnt = 0;
+      FOR_EACH_IMM_USE_STMT (op_use_stmt, imm_iter, op)
+	if (!is_gimple_debug (op_use_stmt)
+	    && (*code != ERROR_MARK
+		|| flow_bb_inside_loop_p (loop, gimple_bb (op_use_stmt))))
+	  {
+	    /* We want to allow x + x but not x < 1 ? x : 2.  */
+	    if (is_gimple_assign (op_use_stmt)
+		&& gimple_assign_rhs_code (op_use_stmt) == COND_EXPR)
+	      {
+		use_operand_p use_p;
+		FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
+		  cnt++;
+	      }
+	    else
+	      cnt++;
+	  }
+      if (cnt != 1)
+	{
+	  fail = true;
+	  break;
+	}
     }
   return ! fail && ! neg && *code != ERROR_MARK;
 }