[PATCH] Optimize identical permutation in my last r13-3212-gb88adba751da63

[Liwei Xu <liwei.xu@intel.com>]

Add extra index check when merging VEC_CST, this handles the case when exactly op1 needs to be return.

This fixes:
	FAIL: gcc.dg/tree-ssa/forwprop-19.c scan-tree-dump-not forwprop1 "VEC_PERM_EXPR"

gcc/ChangeLog:

	PR target/107220
	* match.pd: Check the index of VEC_CST and return the op1 if needed.
---
 gcc/match.pd | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/gcc/match.pd b/gcc/match.pd
index 3550c16aaa6..1efdc3abb5d 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -8106,6 +8106,7 @@ and,
     vec_perm_builder builder0;
     vec_perm_builder builder1;
     vec_perm_builder builder2 (nelts, nelts, 1);
+    bool ident_to_1 = true;
 
     if (!tree_to_vec_perm_builder (&builder0, @3)
 	|| !tree_to_vec_perm_builder (&builder1, @4))
@@ -8115,7 +8116,15 @@ and,
     vec_perm_indices sel1 (builder1, 1, nelts);
 
     for (int i = 0; i < nelts; i++)
-      builder2.quick_push (sel0[sel1[i].to_constant ()]);
+      {
+	 int tmp_index = sel0[sel1[i].to_constant ()].to_constant ();
+	 builder2.quick_push (sel0[sel1[i].to_constant ()]);
+	 if ( i != tmp_index)
+	  ident_to_1 = false;
+      }
+
+    if (ident_to_1)
+      return @1;
 
     vec_perm_indices sel2 (builder2, 2, nelts);
 
-- 
2.18.2