Add find_gelu_erf to simplify_alegrbra

src/simplify_algebra.cpp

@@ -851,6 +851,54 @@ struct find_div_const
     }
 };
 
+struct find_gelu_erf
+{
+    static auto match_mul1()
+    {
+        return match::name("mul")(args(match::any().bind("x"), match::skip_broadcasts(match::name("recip"))));
+    }
+
+    static auto match_erf() { return match::name("erf")(match::arg(0)(match_mul1())); }
+
+    static auto match_add2()
+    {
+        return match::name("add")(args(match_erf(), match::skip_broadcasts(match::has_value(1.0f))));
+    }
+
+    static auto match_add1()
+    {
+        return match::name("add")(args(match::skip_broadcasts(match::is_constant()), match::name("dot")));
+    }
+
+    static auto match_mul2() { return match::name("mul")(match::args(match_add1(), match_add2())); }
+
+    auto matcher() const
+    {
+        return match::name("mul")(
+            match::args(match_mul2(), match::skip_broadcasts(match::has_value(0.5f))));
+    }
+
+    void apply(module& m, const match::matcher_result& r) const
+    {
+        auto ins     = r.result;
+        auto x = r.instructions["x"];
+
+        auto lit = m.add_literal(literal{shape{x->get_shape().type()}, {1.702f}});
+        auto mul = m.insert_instruction(
+            ins, make_op("multibroadcast", {{"out_lens", x->get_shape().lens()}}), lit);
+        mul      = m.insert_instruction(ins, make_op("mul"), x, mul);
+        auto sig = m.insert_instruction(ins, make_op("neg"), mul);
+        auto one = m.add_literal(literal{shape{x->get_shape().type()}, {1.0f}});
+        one = m.insert_instruction(
+            ins, make_op("multibroadcast", {{"out_lens", x->get_shape().lens()}}), one);
+        sig = m.insert_instruction(ins, make_op("exp"), sig);
+        sig = m.insert_instruction(ins, make_op("add"), one, sig);
+        sig = m.insert_instruction(ins, make_op("div"), one, sig);
+        sig  = m.insert_instruction(ins, make_op("mul"), x, sig);
+        m.replace_instruction(ins, sig);
+    }
+};
+
 struct find_sub_const
 {
     auto matcher() const
@@ -1040,6 +1088,7 @@ void simplify_algebra::apply(module& m) const
     for(int i = 0; i < 8; i++)
     {
         match::find_matches(m,
+                            find_gelu_erf{},
                             find_inner_broadcast{},
                             find_double_add_lit_broadcast{},
                             find_add_lit_broadcast{},