From: Richard Biener <rguenther@suse.de>
Date: Tue, 13 Jan 2026 11:59:41 +0000 (+0100)
Subject: middle-end/123573 - fix VEC_PERM folding more
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e787d5ace5cc315892868f3e5e2a2a16fd31bcc8;p=thirdparty%2Fgcc.git

middle-end/123573 - fix VEC_PERM folding more

The following fixes the fix from r16-6709-ga4716ece529dfd some
more by making sure permute to one operand folding faces same
element number vectors but also insert a VIEW_CONVERT_EXPR for
the case one is VLA and one is VLS (when the VLA case is actually
constant, like with -msve-vector-bits=128).  It also makes the
assert that output and input element numbers match done in
fold_vec_perm which this pattern eventually dispatches to into
a check (as the comment already indicates).

Testcases are in the target specific aarch64 testsuite already.

	PR middle-end/123573
	* fold-const.cc (fold_vec_perm): Actually check, not assert,
	that input and output vector element numbers agree.
	* match.pd (vec_perm @0 @1 @2): Make sure element numbers
	are the same when folding to an input vector and wrap that
	inside a VIEW_CONVERT_EXPR.
---

diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 52c92ad66b5..f7b712f0c78 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -10704,11 +10704,10 @@ fold_vec_perm (tree type, tree arg0, tree arg1, const vec_perm_indices &sel)
 
   /* For fall back case, we want to ensure we have VLS vectors
      with equal length.  */
-  if (!sel.length ().is_constant (&nelts))
+  if (!sel.length ().is_constant (&nelts)
+      || !known_eq (sel.length (), TYPE_VECTOR_SUBPARTS (TREE_TYPE (arg0))))
     return NULL_TREE;
 
-  gcc_assert (known_eq (sel.length (),
-			TYPE_VECTOR_SUBPARTS (TREE_TYPE (arg0))));
   tree *in_elts = XALLOCAVEC (tree, nelts * 2);
   if (!vec_cst_ctor_to_array (arg0, nelts, in_elts)
       || !vec_cst_ctor_to_array (arg1, nelts, in_elts + nelts))
diff --git a/gcc/match.pd b/gcc/match.pd
index c339762b90c..f29f7638d66 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -11528,9 +11528,9 @@ and,
       vec_perm_indices sel (builder, single_arg ? 1 : 2, nelts_in);
     }
     (if (known_eq (nelts, nelts_in) && sel.series_p (0, 1, 0, 1))
-     { op0; }
-     (if (sel.series_p (0, 1, nelts_in, 1))
-      { op1; }
+     (view_convert @0)
+     (if (known_eq (nelts, nelts_in) && sel.series_p (0, 1, nelts_in, 1))
+      (view_convert @1)
       (with
        {
          if (!single_arg)