i965/vec4: add helpers for conversions to/from doubles

Use these helpers to implement d2f and f2d. We will reuse these helpers when
we implement things like d2i or i2d as well.

v2:
- Rename the helpers (Matt)

Reviewed-by: Matt Turner <mattst88@gmail.com>
diff --git a/src/mesa/drivers/dri/i965/brw_vec4.h b/src/mesa/drivers/dri/i965/brw_vec4.h
index 625ab9e..396e158 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.h
+++ b/src/mesa/drivers/dri/i965/brw_vec4.h
@@ -315,6 +315,11 @@
 
    bool optimize_predicate(nir_alu_instr *instr, enum brw_predicate *predicate);
 
+   void emit_conversion_from_double(dst_reg dst, src_reg src, bool saturate,
+                                    brw_reg_type single_type);
+   void emit_conversion_to_double(dst_reg dst, src_reg src, bool saturate,
+                                  brw_reg_type single_type);
+
    virtual void emit_nir_code();
    virtual void nir_setup_uniforms();
    virtual void nir_setup_system_value_intrinsic(nir_intrinsic_instr *instr);
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp b/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
index 78f5218..4aeb8cb 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
@@ -1067,6 +1067,36 @@
 }
 
 void
+vec4_visitor::emit_conversion_from_double(dst_reg dst, src_reg src,
+                                          bool saturate,
+                                          brw_reg_type single_type)
+{
+   dst_reg temp = dst_reg(this, glsl_type::dvec4_type);
+   emit(MOV(temp, src));
+
+   dst_reg temp2 = dst_reg(this, glsl_type::dvec4_type);
+   temp2 = retype(temp2, single_type);
+   emit(VEC4_OPCODE_FROM_DOUBLE, temp2, src_reg(temp))
+      ->size_written = 2 * REG_SIZE;
+
+   vec4_instruction *inst = emit(MOV(dst, src_reg(temp2)));
+   inst->saturate = saturate;
+}
+
+void
+vec4_visitor::emit_conversion_to_double(dst_reg dst, src_reg src,
+                                        bool saturate,
+                                        brw_reg_type single_type)
+{
+   dst_reg tmp_dst = dst_reg(src_reg(this, glsl_type::dvec4_type));
+   src_reg tmp_src = retype(src_reg(this, glsl_type::vec4_type), single_type);
+   emit(MOV(dst_reg(tmp_src), retype(src, single_type)));
+   emit(VEC4_OPCODE_TO_DOUBLE, tmp_dst, tmp_src);
+   vec4_instruction *inst = emit(MOV(dst, src_reg(tmp_dst)));
+   inst->saturate = saturate;
+}
+
+void
 vec4_visitor::nir_emit_alu(nir_alu_instr *instr)
 {
    vec4_instruction *inst;
@@ -1110,29 +1140,15 @@
       inst = emit(MOV(dst, op[0]));
       break;
 
-   case nir_op_d2f: {
-      dst_reg temp = dst_reg(this, glsl_type::dvec4_type);
-      emit(MOV(temp, op[0]));
-
-      dst_reg temp2 = dst_reg(this, glsl_type::dvec4_type);
-      temp2 = retype(temp2, BRW_REGISTER_TYPE_F);
-      emit(VEC4_OPCODE_FROM_DOUBLE, temp2, src_reg(temp))
-         ->size_written = 2 * REG_SIZE;
-
-      vec4_instruction *inst = emit(MOV(dst, src_reg(temp2)));
-      inst->saturate = instr->dest.saturate;
+   case nir_op_d2f:
+      emit_conversion_from_double(dst, op[0], instr->dest.saturate,
+                                  BRW_REGISTER_TYPE_F);
       break;
-   }
 
-   case nir_op_f2d: {
-      dst_reg tmp_dst = dst_reg(src_reg(this, glsl_type::dvec4_type));
-      src_reg tmp_src = src_reg(this, glsl_type::vec4_type);
-      emit(MOV(dst_reg(tmp_src), retype(op[0], BRW_REGISTER_TYPE_F)));
-      emit(VEC4_OPCODE_TO_DOUBLE, tmp_dst, tmp_src);
-      vec4_instruction *inst = emit(MOV(dst, src_reg(tmp_dst)));
-      inst->saturate = instr->dest.saturate;
+   case nir_op_f2d:
+      emit_conversion_to_double(dst, op[0], instr->dest.saturate,
+                                BRW_REGISTER_TYPE_F);
       break;
-   }
 
    case nir_op_iadd:
       assert(nir_dest_bit_size(instr->dest.dest) < 64);