i965/fs: Add a helper function for checking for partial register updates.

These checks were all over, and every time I wrote one I had to try to
decide again what the cases were for partial updates.

v2: Fix inadvertent reladdr check removal.
Reviewed-by: Matt Turner <mattst88@gmail.com>

src/mesa/drivers/dri/i965/brw_fs.cpp

@@ -710,6 +710,22 @@ fs_visitor::pop_force_sechalf()
    assert(force_sechalf_stack >= 0);
 }
 
+/**
+ * Returns true if the instruction has a flag that means it won't
+ * update an entire destination register.
+ *
+ * For example, dead code elimination and live variable analysis want to know
+ * when a write to a variable screens off any preceding values that were in
+ * it.
+ */
+bool
+fs_inst::is_partial_write()
+{
+   return (this->predicate ||
+           this->force_uncompressed ||
+           this->force_sechalf);
+}
+
 /**
  * Returns how many MRFs an FS opcode will write over.
  *
@@ -2065,22 +2081,14 @@ fs_visitor::compute_to_mrf()
 	     * into a compute-to-MRF.
 	     */
 
-	    /* If it's predicated, it (probably) didn't populate all
-	     * the channels.  We might be able to rewrite everything
+	    /* If this one instruction didn't populate all the
+	     * channels, bail.  We might be able to rewrite everything
 	     * that writes that reg, but it would require smarter
 	     * tracking to delay the rewriting until complete success.
 	     */
-	    if (scan_inst->predicate)
+	    if (scan_inst->is_partial_write())
 	       break;
 
-	    /* If it's half of register setup and not the same half as
-	     * our MOV we're trying to remove, bail for now.
-	     */
-	    if (scan_inst->force_uncompressed != inst->force_uncompressed ||
-		scan_inst->force_sechalf != inst->force_sechalf) {
-	       break;
-	    }
-
             /* Things returning more than one register would need us to
              * understand coalescing out more than one MOV at a time.
              */
@@ -2662,9 +2670,7 @@ fs_visitor::get_instruction_generating_reg(fs_inst *start,
 					   fs_reg reg)
 {
    if (end == start ||
-       end->predicate ||
-       end->force_uncompressed ||
-       end->force_sechalf ||
+       end->is_partial_write() ||
        reg.reladdr ||
        !reg.equals(end->dst)) {
       return NULL;

src/mesa/drivers/dri/i965/brw_fs.h

@@ -179,6 +179,7 @@ public:
    bool is_math();
    bool is_control_flow();
    bool is_send_from_grf();
+   bool is_partial_write();
 
    fs_reg dst;
    fs_reg src[3];

src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp

@@ -414,9 +414,7 @@ fs_visitor::opt_copy_propagate_local(void *mem_ctx, bblock_t *block,
            inst->src[0].file == IMM) &&
 	  inst->src[0].type == inst->dst.type &&
 	  !inst->saturate &&
-	  !inst->predicate &&
-	  !inst->force_uncompressed &&
-	  !inst->force_sechalf) {
+	  !inst->is_partial_write()) {
 	 acp_entry *entry = ralloc(mem_ctx, acp_entry);
 	 entry->dst = inst->dst;
 	 entry->src = inst->src[0];

src/mesa/drivers/dri/i965/brw_fs_cse.cpp

@@ -97,8 +97,7 @@ fs_visitor::opt_cse_local(bblock_t *block, exec_list *aeb)
 	inst = (fs_inst *) inst->next) {
 
       /* Skip some cases. */
-      if (is_expression(inst) && !inst->predicate &&
-          !inst->force_uncompressed && !inst->force_sechalf &&
+      if (is_expression(inst) && !inst->is_partial_write() &&
           !inst->conditional_mod)
       {
 	 bool found = false;

src/mesa/drivers/dri/i965/brw_fs_live_variables.cpp

@@ -78,9 +78,7 @@ fs_live_variables::setup_def_use()
 	  */
 	 if (inst->dst.file == GRF &&
 	     inst->regs_written == v->virtual_grf_sizes[inst->dst.reg] &&
-	     !inst->predicate &&
-	     !inst->force_uncompressed &&
-	     !inst->force_sechalf) {
+	     !inst->is_partial_write()) {
 	    int reg = inst->dst.reg;
             if (!BITSET_TEST(bd[b].use, reg))
                BITSET_SET(bd[b].def, reg);