v3d: Add a helper function for getting a nop register.

Just a little refactor to explain what's going on with QFILE_NULL.

src/broadcom/compiler/nir_to_vir.c

@@ -698,7 +698,7 @@ ntq_emit_comparison(struct v3d_compile *c,
         if (nir_op_infos[compare_instr->op].num_inputs > 1)
                 src1 = ntq_get_alu_src(c, compare_instr, 1);
         bool cond_invert = false;
-        struct qreg nop = vir_reg(QFILE_NULL, 0);
+        struct qreg nop = vir_nop_reg();
 
         switch (compare_instr->op) {
         case nir_op_feq32:
@@ -1116,7 +1116,7 @@ emit_frag_end(struct v3d_compile *c)
                 struct nir_variable *var = c->output_color_var[0];
                 struct qreg *color = &c->outputs[var->data.driver_location * 4];
 
-                vir_SETMSF_dest(c, vir_reg(QFILE_NULL, 0),
+                vir_SETMSF_dest(c, vir_nop_reg(),
                                 vir_AND(c,
                                         vir_MSF(c),
                                         vir_FTOC(c, color[3])));
@@ -1153,7 +1153,7 @@ emit_frag_end(struct v3d_compile *c)
 
                 struct qinst *inst = vir_MOV_dest(c,
                                                   vir_reg(QFILE_TLBU, 0),
-                                                  vir_reg(QFILE_NULL, 0));
+                                                  vir_nop_reg());
                 uint8_t tlb_specifier = TLB_TYPE_DEPTH;
 
                 if (c->devinfo->ver >= 42) {
@@ -1888,11 +1888,11 @@ ntq_emit_intrinsic(struct v3d_compile *c, nir_intrinsic_instr *instr)
         case nir_intrinsic_discard:
                 if (c->execute.file != QFILE_NULL) {
                         vir_PF(c, c->execute, V3D_QPU_PF_PUSHZ);
-                        vir_set_cond(vir_SETMSF_dest(c, vir_reg(QFILE_NULL, 0),
+                        vir_set_cond(vir_SETMSF_dest(c, vir_nop_reg(),
                                                      vir_uniform_ui(c, 0)),
                                 V3D_QPU_COND_IFA);
                 } else {
-                        vir_SETMSF_dest(c, vir_reg(QFILE_NULL, 0),
+                        vir_SETMSF_dest(c, vir_nop_reg(),
                                         vir_uniform_ui(c, 0));
                 }
                 break;
@@ -1908,12 +1908,12 @@ ntq_emit_intrinsic(struct v3d_compile *c, nir_intrinsic_instr *instr)
                          */
                         vir_PF(c, vir_OR(c, c->execute, vir_NOT(c, cond)),
                                V3D_QPU_PF_PUSHZ);
-                        vir_set_cond(vir_SETMSF_dest(c, vir_reg(QFILE_NULL, 0),
+                        vir_set_cond(vir_SETMSF_dest(c, vir_nop_reg(),
                                                      vir_uniform_ui(c, 0)),
                                      V3D_QPU_COND_IFA);
                 } else {
                         vir_PF(c, cond, V3D_QPU_PF_PUSHZ);
-                        vir_set_cond(vir_SETMSF_dest(c, vir_reg(QFILE_NULL, 0),
+                        vir_set_cond(vir_SETMSF_dest(c, vir_nop_reg(),
                                                      vir_uniform_ui(c, 0)),
                                      V3D_QPU_COND_IFNA);
                 }
@@ -2008,7 +2008,7 @@ ntq_emit_intrinsic(struct v3d_compile *c, nir_intrinsic_instr *instr)
 static void
 ntq_activate_execute_for_block(struct v3d_compile *c)
 {
-        vir_set_pf(vir_XOR_dest(c, vir_reg(QFILE_NULL, 0),
+        vir_set_pf(vir_XOR_dest(c, vir_nop_reg(),
                                 c->execute, vir_uniform_ui(c, c->cur_block->index)),
                    V3D_QPU_PF_PUSHZ);
 
@@ -2106,8 +2106,7 @@ ntq_emit_nonuniform_if(struct v3d_compile *c, nir_if *if_stmt)
         if (was_top_level) {
                 cond = v3d_qpu_cond_invert(cond);
         } else {
-                struct qinst *inst = vir_MOV_dest(c, vir_reg(QFILE_NULL, 0),
+                struct qinst *inst = vir_MOV_dest(c, vir_nop_reg(), c->execute);
-                                                  c->execute);
                 if (cond == V3D_QPU_COND_IFA) {
                         vir_set_uf(inst, V3D_QPU_UF_NORNZ);
                 } else {

src/broadcom/compiler/qpu_schedule.c

@@ -1028,7 +1028,7 @@ insert_scheduled_instruction(struct v3d_compile *c,
 static struct qinst *
 vir_nop()
 {
-        struct qreg undef = { QFILE_NULL, 0 };
+        struct qreg undef = vir_nop_reg();
         struct qinst *qinst = vir_add_inst(V3D_QPU_A_NOP, undef, undef, undef);
 
         return qinst;

src/broadcom/compiler/v3d_compiler.h

@@ -105,6 +105,11 @@ static inline struct qreg vir_reg(enum qfile file, uint32_t index)
         return (struct qreg){file, index};
 }
 
+static inline struct qreg vir_nop_reg(void)
+{
+        return (struct qreg){QFILE_NULL, 0};
+}
+
 /**
  * A reference to an actual register at the QPU level, for register
  * allocation.

src/broadcom/compiler/vir.c

@@ -401,7 +401,7 @@ vir_branch_inst(enum v3d_qpu_branch_cond cond, struct qreg src)
         inst->qpu.branch.ub = true;
         inst->qpu.branch.bdu = V3D_QPU_BRANCH_DEST_REL;
 
-        inst->dst = vir_reg(QFILE_NULL, 0);
+        inst->dst = vir_nop_reg();
         inst->src[0] = src;
         inst->uniform = ~0;
 
@@ -1098,7 +1098,7 @@ vir_PF(struct v3d_compile *c, struct qreg src, enum v3d_qpu_pf pf)
             last_inst != c->defs[src.index] ||
             !vir_can_set_flags(c, last_inst)) {
                 /* XXX: Make the MOV be the appropriate type */
-                last_inst = vir_MOV_dest(c, vir_reg(QFILE_NULL, 0), src);
+                last_inst = vir_MOV_dest(c, vir_nop_reg(), src);
         }
 
         vir_set_pf(last_inst, pf);

src/broadcom/compiler/vir_to_qpu.c

@@ -76,7 +76,7 @@ v3d_qpu_nop(void)
 static struct qinst *
 vir_nop(void)
 {
-        struct qreg undef = { QFILE_NULL, 0 };
+        struct qreg undef = vir_nop_reg();
         struct qinst *qinst = vir_add_inst(V3D_QPU_A_NOP, undef, undef, undef);
 
         return qinst;