From: Richard Biener <rguenther@suse.de>
Date: Mon, 8 Dec 2025 10:06:54 +0000 (+0100)
Subject: tree-optimization/123040 - handle nary -> ifn simplification in VN
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5a6d911ca2e253297bc2f3be9d9db2a71a244a94;p=thirdparty%2Fgcc.git

tree-optimization/123040 - handle nary -> ifn simplification in VN

The following handles (by rejecting) simplifications that end up
turning a VN NARY operation into a call which would be a VN REFERENCE
and is unexpected and not handled.

	PR tree-optimization/123040
	* tree-ssa-sccvn.cc (vn_nary_build_or_lookup_1): Only insert
	nary results.

	* g++.dg/torture/pr123040.C: New testcase.
---

diff --git a/gcc/testsuite/g++.dg/torture/pr123040.C b/gcc/testsuite/g++.dg/torture/pr123040.C
new file mode 100644
index 00000000000..3ba2d909f69
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr123040.C
@@ -0,0 +1,61 @@
+// { dg-do compile }
+
+template <int kBytes, typename From, typename To>
+void CopyBytes(From from, To to) {
+  __builtin_memcpy(to, from, kBytes);
+}
+template <typename From, typename To> void CopySameSize(From *from, To to) {
+  CopyBytes<sizeof(From)>(from, to);
+}
+template <typename> using MakeUnsigned = char;
+template <typename Lane, int N> struct Simd {
+  using T = Lane;
+  static constexpr int kPrivateLanes = N;
+  template <typename NewT> using Rebind = Simd<NewT, 0>;
+};
+template <class D> using TFromD = D::T;
+template <class T, class D> using Rebind = D::template Rebind<T>;
+template <class D> using RebindToUnsigned = Rebind<MakeUnsigned<D>, D>;
+template <typename T, int> struct Vec128 {
+  using PrivateT = T;
+  static constexpr int kPrivateN = 6;
+  T raw[16];
+};
+template <class V> using DFromV = Simd<typename V::PrivateT, V::kPrivateN>;
+template <class D> Vec128<TFromD<D>, D::kPrivateLanes> Zero(D);
+template <class D> using VFromD = decltype(Zero(D()));
+template <class D, class VFrom> VFromD<D> BitCast(D, VFrom v) {
+  VFromD<D> to;
+  CopySameSize(&v, to.raw);
+  return to;
+}
+template <int N> Vec128<signed char, N> And(Vec128<signed char, N> b) {
+  Vec128<signed char, N> a;
+  DFromV<decltype(a)> d;
+  RebindToUnsigned<decltype(d)> du;
+  auto au(a);
+  auto bu = BitCast(du, b);
+  for (int i = 0; i < N; ++i)
+    au.raw[i] &= bu.raw[i];
+  return au;
+}
+void Or(Vec128<signed char, 16>);
+template <int N> void IfVecThenElse(Vec128<signed char, N> yes) {
+  Vec128 __trans_tmp_2 = And(yes);
+  Or(__trans_tmp_2);
+}
+template <int N> void IfThenElseZero(Vec128<signed char, N> yes) {
+  IfVecThenElse(yes);
+}
+Vec128<signed char, 16> Abs_a;
+char MaskedAbs___trans_tmp_5;
+void MaskedAbs() {
+  Vec128<signed char, 16> __trans_tmp_4;
+  for (int i = 0; i < 16; ++i) {
+    MaskedAbs___trans_tmp_5 = Abs_a.raw[i] ? -Abs_a.raw[i] : 0;
+    Abs_a.raw[i] = MaskedAbs___trans_tmp_5;
+  }
+  __trans_tmp_4 = Abs_a;
+  Vec128 __trans_tmp_3 = __trans_tmp_4;
+  IfThenElseZero(__trans_tmp_3);
+}
diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index 09f92b2efc1..0c519cf4c21 100644
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -2527,7 +2527,10 @@ vn_nary_build_or_lookup_1 (gimple_match_op *res_op, bool insert,
   else
     {
       tree val = vn_lookup_simplify_result (res_op);
-      if (!val && insert)
+      /* ???  In weird cases we can end up with internal-fn calls,
+	 but this isn't expected so throw the result away.  See
+	 PR123040 for an example.  */
+      if (!val && insert && res_op->code.is_tree_code ())
 	{
 	  gimple_seq stmts = NULL;
 	  result = maybe_push_res_to_seq (res_op, &stmts);