diff --git a/src/compiler/glsl/glsl_to_nir.cpp b/src/compiler/glsl/glsl_to_nir.cpp
index 456efa9d583..27d6d4c3b9e 100644
--- a/src/compiler/glsl/glsl_to_nir.cpp
+++ b/src/compiler/glsl/glsl_to_nir.cpp
@@ -667,13 +667,8 @@ nir_visitor::create_function(ir_function_signature *ir)
       /* FINISHME: pass arrays, structs, etc by reference? */
       assert(glsl_type_is_vector(param->type) || glsl_type_is_scalar(param->type));
 
-      if (param->data.mode == ir_var_function_in) {
-         func->params[np].num_components = param->type->vector_elements;
-         func->params[np].bit_size = glsl_get_bit_size(param->type);
-      } else {
-         func->params[np].num_components = 1;
-         func->params[np].bit_size = 32;
-      }
+      func->params[np].num_components = 1;
+      func->params[np].bit_size = 32;
       np++;
    }
    assert(np == func->num_params);
@@ -710,20 +705,6 @@ nir_visitor::visit(ir_function_signature *ir)
 
       b = nir_builder_at(nir_after_impl(impl));
 
-      unsigned i = (ir->return_type != &glsl_type_builtin_void) ? 1 : 0;
-
-      foreach_in_list(ir_variable, param, &ir->parameters) {
-         nir_variable *var =
-            nir_local_variable_create(impl, param->type, param->name);
-
-         if (param->data.mode == ir_var_function_in) {
-            nir_store_var(&b, var, nir_load_param(&b, i), ~0);
-         }
-
-         _mesa_hash_table_insert(var_table, param, var);
-         i++;
-      }
-
       visit_exec_list(&ir->body, this);
 
       this->is_global = true;
@@ -837,6 +818,12 @@ deref_get_qualifier(nir_deref_instr *deref)
    nir_deref_path path;
    nir_deref_path_init(&path, deref, NULL);
 
+   /* Function params can lead to a deref cast just return zero as these
+    * params have no qualifers anyway.
+    */
+   if (path.path[0]->deref_type != nir_deref_type_var)
+      return (gl_access_qualifier) 0;
+
    unsigned qualifiers = path.path[0]->var->data.access;
 
    const glsl_type *parent_type = path.path[0]->type;
@@ -1532,25 +1519,20 @@ nir_visitor::visit(ir_call *ir)
       ir_rvalue *param_rvalue = (ir_rvalue *) actual_node;
       ir_variable *sig_param = (ir_variable *) formal_node;
 
-      if (sig_param->data.mode == ir_var_function_out ||
+      nir_variable *param =
+         nir_local_variable_create(this->impl, sig_param->type, "param");
+      param->data.precision = sig_param->data.precision;
+      nir_deref_instr *param_deref = nir_build_deref_var(&b, param);
+
+      if (sig_param->data.mode == ir_var_function_in ||
           sig_param->data.mode == ir_var_function_inout) {
-         nir_variable *out_param =
-            nir_local_variable_create(this->impl, sig_param->type, "param");
-         out_param->data.precision = sig_param->data.precision;
-         nir_deref_instr *out_param_deref = nir_build_deref_var(&b, out_param);
-
-         if (sig_param->data.mode == ir_var_function_inout) {
-            nir_store_deref(&b, out_param_deref,
-                            nir_load_deref(&b, evaluate_deref(param_rvalue)),
-                            ~0);
-         }
-
-         call->params[i] = nir_src_for_ssa(&out_param_deref->def);
-      } else if (sig_param->data.mode == ir_var_function_in) {
-         nir_def *val = evaluate_rvalue(param_rvalue);
-         call->params[i] = nir_src_for_ssa(val);
+         nir_store_deref(&b, param_deref,
+                         evaluate_rvalue(param_rvalue),
+                         ~0);
       }
 
+      call->params[i] = nir_src_for_ssa(&param_deref->def);
+
       i++;
    }
 
@@ -2509,7 +2491,8 @@ void
 nir_visitor::visit(ir_dereference_variable *ir)
 {
    if (ir->variable_referenced()->data.mode == ir_var_function_out ||
-       ir->variable_referenced()->data.mode == ir_var_function_inout) {
+       ir->variable_referenced()->data.mode == ir_var_function_inout ||
+       ir->variable_referenced()->data.mode == ir_var_function_in) {
       unsigned i = (sig->return_type != &glsl_type_builtin_void) ? 1 : 0;
 
       foreach_in_list(ir_variable, param, &sig->parameters) {
diff --git a/src/compiler/glsl/tests/test_gl_lower_mediump.cpp b/src/compiler/glsl/tests/test_gl_lower_mediump.cpp
index 312afce4d47..9177c3d7272 100644
--- a/src/compiler/glsl/tests/test_gl_lower_mediump.cpp
+++ b/src/compiler/glsl/tests/test_gl_lower_mediump.cpp
@@ -438,10 +438,7 @@ TEST_F(gl_nir_lower_mediump_test, func_args_in_mediump)
 
    EXPECT_PRED_FORMAT2(glsl_ir_contains, fs_ir, "expression float f162f (expression float16_t * (expression float16_t f2fmp (var_ref x) ) (expression float16_t f2fmp (var_ref y) ) )");
 
-   /* NIR optimization will notice that we downconvert the highp to mediump just
-    * to multiply and cast back up, and just multiply in highp instead.
-    */
-   EXPECT_EQ(op_dest_bits(nir_op_fmul), 32);
+   EXPECT_EQ(op_dest_bits(nir_op_fmul), 16);
 }
 
 TEST_F(gl_nir_lower_mediump_test, func_args_inout_mediump)
diff --git a/src/compiler/nir/nir_lower_double_ops.c b/src/compiler/nir/nir_lower_double_ops.c
index 1c8933de702..92e57ce1f60 100644
--- a/src/compiler/nir/nir_lower_double_ops.c
+++ b/src/compiler/nir/nir_lower_double_ops.c
@@ -645,8 +645,21 @@ lower_doubles_instr_to_soft(nir_builder *b, nir_alu_instr *instr,
 
    assert(nir_op_infos[instr->op].num_inputs + 1 == func->num_params);
    for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
+      nir_alu_type n_type =
+         nir_alu_type_get_base_type(nir_op_infos[instr->op].input_types[i]);
+      /* Add bitsize */
+      n_type = n_type | instr->src[0].src.ssa->bit_size;
+
+      const struct glsl_type *param_type =
+         glsl_scalar_type(nir_get_glsl_base_type_for_nir_type(n_type));
+
+      nir_variable *param =
+         nir_local_variable_create(b->impl, param_type, "param");
+      nir_deref_instr *param_deref = nir_build_deref_var(b, param);
+      nir_store_deref(b, param_deref, nir_mov_alu(b, instr->src[i], 1), ~0);
+
       assert(i + 1 < ARRAY_SIZE(params));
-      params[i + 1] = nir_mov_alu(b, instr->src[i], 1);
+      params[i + 1] = &param_deref->def;
    }
 
    nir_inline_function_impl(b, func->impl, params, NULL);