nir: test opt_loop_merge_terminators() skips unhandled loops

This test makes sure the merge if pass skips loops with trainling phis
as those are not handled by the pass.

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29686>

src/compiler/nir/tests/opt_loop_tests.cpp

@@ -27,6 +27,10 @@ class nir_opt_loop_test : public nir_test {
 protected:
    nir_opt_loop_test();
 
+   nir_deref_instr *add_loop_terminators(nir_if **term1, nir_if **term2);
+   void create_loop_phis(nir_loop *loop, nir_if *term1, nir_if *term2,
+                         nir_def *def1, nir_def *def2);
+
    nir_def *in_def;
    nir_variable *out_var;
    nir_variable *ubo_var;
@@ -43,13 +47,9 @@ nir_opt_loop_test::nir_opt_loop_test()
    out_var = nir_variable_create(b->shader, nir_var_shader_out, glsl_int_type(), "out");
 }
 
-TEST_F(nir_opt_loop_test, opt_loop_merge_terminators_deref_after_first_if)
+nir_deref_instr *
+nir_opt_loop_test::add_loop_terminators(nir_if **term1, nir_if **term2)
 {
-   /* Tests that opt_loop_merge_terminators creates valid nir after it merges
-    * terminators that have a deref statement between them:
-    */
-   nir_loop *loop = nir_push_loop(b);
-
    /* Add first terminator */
    nir_def *one = nir_imm_int(b, 1);
    nir_def *cmp_result = nir_ieq(b, in_def, one);
@@ -57,6 +57,9 @@ TEST_F(nir_opt_loop_test, opt_loop_merge_terminators_deref_after_first_if)
    nir_jump(b, nir_jump_break);
    nir_pop_if(b, nif);
 
+   if (term1)
+      *term1 = nif;
+
    nir_deref_instr *deref = nir_build_deref_var(b, ubo_var);
    nir_def *ubo_def = nir_load_deref(b, deref);
 
@@ -67,11 +70,40 @@ TEST_F(nir_opt_loop_test, opt_loop_merge_terminators_deref_after_first_if)
    nir_jump(b, nir_jump_break);
    nir_pop_if(b, nif2);
 
+   if (term2)
+      *term2 = nif2;
+
+   return deref;
+}
+
+void
+nir_opt_loop_test::create_loop_phis(nir_loop *loop,
+                                    nir_if *term1, nir_if *term2,
+                                    nir_def *def1, nir_def *def2)
+{
+   nir_phi_instr *phi_instr = nir_phi_instr_create(b->shader);
+   nir_def_init(&phi_instr->instr, &phi_instr->def, 1, 32);
+   nir_phi_instr_add_src(phi_instr, nir_if_first_then_block(term1), def1);
+   nir_phi_instr_add_src(phi_instr, nir_if_first_then_block(term2), def2);
+
+   nir_instr_insert(nir_after_cf_node(&loop->cf_node),
+                    &phi_instr->instr);
+}
+
+TEST_F(nir_opt_loop_test, opt_loop_merge_terminators_deref_after_first_if)
+{
+   /* Tests that opt_loop_merge_terminators creates valid nir after it merges
+    * terminators that have a deref statement between them:
+    */
+   nir_loop *loop = nir_push_loop(b);
+
+   nir_deref_instr *deref = add_loop_terminators(NULL, NULL);
+
    /* Load from deref that will be moved inside the continue branch of the
     * first if-statements continue block. If not handled correctly during
     * the merge this will fail nir validation.
     */
-   ubo_def = nir_load_deref(b, deref);
+   nir_def *ubo_def = nir_load_deref(b, deref);
    nir_store_var(b, out_var, ubo_def, 1);
 
    nir_pop_loop(b, loop);
@@ -80,3 +112,55 @@ TEST_F(nir_opt_loop_test, opt_loop_merge_terminators_deref_after_first_if)
 
    nir_validate_shader(b->shader, NULL);
 }
+
+TEST_F(nir_opt_loop_test, opt_loop_merge_terminators_skip_merge_if_phis)
+{
+   /* Tests that opt_loop_merge_terminators skips merging the terminators if
+    * the loop has phis. We can update or remove this test if support for
+    * phis is added to this pass:
+    */
+   nir_deref_instr *deref = nir_build_deref_var(b, ubo_var);
+   nir_def *ubo_def = nir_load_deref(b, deref);
+
+   nir_loop *loop = nir_push_loop(b);
+
+   nir_if *term1;
+   nir_if *term2;
+   add_loop_terminators(&term1, &term2);
+
+   nir_pop_loop(b, loop);
+
+   create_loop_phis(loop, term1, term2, in_def, ubo_def);
+
+   ASSERT_FALSE(nir_opt_loop(b->shader));
+
+   nir_validate_shader(b->shader, NULL);
+}
+
+TEST_F(nir_opt_loop_test, opt_loop_merge_terminators_skip_merge_if_phis_nested_loop)
+{
+   /* Tests that opt_loop_merge_terminators skips merging the terminators if
+    * the loop has phis. We can update or remove this test if support for
+    * phis is added to this pass:
+    */
+   nir_deref_instr *deref = nir_build_deref_var(b, ubo_var);
+   nir_def *ubo_def = nir_load_deref(b, deref);
+
+   nir_loop *loop = nir_push_loop(b);
+
+   /* Add a nested loop to make sure we test the correct loop for trailing phis */
+   nir_loop *nested_loop = nir_push_loop(b);
+   nir_pop_loop(b, nested_loop);
+
+   nir_if *term1;
+   nir_if *term2;
+   add_loop_terminators(&term1, &term2);
+
+   nir_pop_loop(b, loop);
+
+   create_loop_phis(loop, term1, term2, in_def, ubo_def);
+
+   ASSERT_FALSE(nir_opt_loop(b->shader));
+
+   nir_validate_shader(b->shader, NULL);
+}