Simplify x - 0 and 0 - x operations

Using the unit/neg unit matchers to handle subtraction operations in the same steps. Added unit tests for both cases.

src/simplify_algebra.cpp

@@ -861,8 +861,9 @@ struct find_unit_ops
             match::name("div")(match::args(match::any().bind("x"), match::has_value(1.0f)));
         auto add_0 = match::name("add")(
             match::either_arg(0, 1)(match::has_value(0.0f), match::any().bind("x")));
-
-        return match::any_of(mul_1, div_1, add_0);
+        auto sub_0 =
+            match::name("sub")(match::args(match::any().bind("x"), match::has_value(0.0f)));
+        return match::any_of(mul_1, div_1, add_0, sub_0);
     }
 
     void apply(module& m, const match::matcher_result& r) const
@@ -882,7 +883,9 @@ struct find_neg_unit_ops
             match::either_arg(0, 1)(match::has_value(-1.0f), match::any().bind("x")));
         auto div_neg_1 =
             match::name("div")(match::args(match::any().bind("x"), match::has_value(-1.0f)));
-        return match::any_of(mul_neg_1, div_neg_1);
+        auto sub_0 =
+            match::name("sub")(match::args(match::has_value(0.0f), match::any().bind("x")));
+        return match::any_of(mul_neg_1, div_neg_1, sub_0);
     }
 
     void apply(module& m, const match::matcher_result& r) const

test/simplify_algebra_test.cpp

@@ -854,6 +854,42 @@ TEST_CASE(simplify_neg_unit_div_const)
     EXPECT(m1 == m2);
 }
 
+TEST_CASE(simplify_sub_zero_const)
+{
+    migraphx::module m1;
+    {
+        auto x    = m1.add_parameter("x", {migraphx::shape::int32_type, {1}});
+        auto zero = m1.add_literal(0);
+        m1.add_instruction(migraphx::make_op("sub"), x, zero);
+    }
+    run_pass(m1);
+
+    migraphx::module m2;
+    {
+        auto x = m2.add_parameter("x", {migraphx::shape::int32_type, {1}});
+        m2.add_instruction(migraphx::make_op("identity"), x);
+    }
+    EXPECT(m1 == m2);
+}
+
+TEST_CASE(simplify_sub_neg_zero_const)
+{
+    migraphx::module m1;
+    {
+        auto x    = m1.add_parameter("x", {migraphx::shape::int32_type, {1}});
+        auto zero = m1.add_literal(0);
+        m1.add_instruction(migraphx::make_op("sub"), zero, x);
+    }
+    run_pass(m1);
+
+    migraphx::module m2;
+    {
+        auto x = m2.add_parameter("x", {migraphx::shape::int32_type, {1}});
+        m2.add_instruction(migraphx::make_op("neg"), x);
+    }
+    EXPECT(m1 == m2);
+}
+
 TEST_CASE(simplify_sub_const)
 {
     migraphx::module m1;