i965/fs.h: Refactor tests for instructions modifying a register.

There's one instance of a potential behavior change: propagate_constants may
now propagate into a part of a vgrf after a different part of it was
overwritten by a send that returns multiple registers.  I don't think we ever
generate IR that meets that condition, but it's something to note if we bisect
behavior change to this.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

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

@@ -167,6 +167,15 @@ fs_inst::regs_written()
    return 1;
 }
 
+bool
+fs_inst::overwrites_reg(const fs_reg &reg)
+{
+   return (reg.file == dst.file &&
+           reg.reg == dst.reg &&
+           reg.reg_offset >= dst.reg_offset  &&
+           reg.reg_offset < dst.reg_offset + regs_written());
+}
+
 bool
 fs_inst::is_tex()
 {
@@ -1400,9 +1409,7 @@ fs_visitor::propagate_constants()
 	 }
 
 	 if (scan_inst->dst.file == GRF &&
-	     scan_inst->dst.reg == inst->dst.reg &&
-	     (scan_inst->dst.reg_offset == inst->dst.reg_offset ||
-	      scan_inst->regs_written() > 1)) {
+             scan_inst->overwrites_reg(inst->dst)) {
 	    break;
 	 }
       }
@@ -1602,16 +1609,8 @@ fs_visitor::register_coalesce()
 	   !scan_inst->is_tail_sentinel();
 	   scan_inst = (fs_inst *)scan_inst->next) {
 	 if (scan_inst->dst.file == GRF) {
-	    if (scan_inst->dst.reg == inst->dst.reg &&
-		(scan_inst->dst.reg_offset == inst->dst.reg_offset ||
-		 scan_inst->regs_written() > 1)) {
-	       interfered = true;
-	       break;
-	    }
-	    if (inst->src[0].file == GRF &&
-		scan_inst->dst.reg == inst->src[0].reg &&
-		(scan_inst->dst.reg_offset == inst->src[0].reg_offset ||
-		 scan_inst->regs_written() > 1)) {
+	    if (scan_inst->overwrites_reg(inst->dst) ||
+                scan_inst->overwrites_reg(inst->src[0])) {
 	       interfered = true;
 	       break;
 	    }

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

@@ -150,6 +150,7 @@ public:
 
    bool equals(fs_inst *inst);
    int regs_written();
+   bool overwrites_reg(const fs_reg &reg);
    bool is_tex();
    bool is_math();
 

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

@@ -98,23 +98,11 @@ fs_visitor::opt_copy_propagate_local(void *mem_ctx,
 
       /* kill the destination from the ACP */
       if (inst->dst.file == GRF) {
-	 int start_offset = inst->dst.reg_offset;
-	 int end_offset = start_offset + inst->regs_written();
-
 	 foreach_list_safe(entry_node, acp) {
 	    acp_entry *entry = (acp_entry *)entry_node;
 
-	    if (entry->dst.file == GRF &&
-		entry->dst.reg == inst->dst.reg &&
-		entry->dst.reg_offset >= start_offset &&
-		entry->dst.reg_offset < end_offset) {
-	       entry->remove();
-	       continue;
-	    }
-	    if (entry->src.file == GRF &&
-		entry->src.reg == inst->dst.reg &&
-		entry->src.reg_offset >= start_offset &&
-		entry->src.reg_offset < end_offset) {
+	    if (inst->overwrites_reg(entry->dst) ||
+                inst->overwrites_reg(entry->src)) {
 	       entry->remove();
 	    }
 	 }

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

@@ -150,17 +150,11 @@ fs_visitor::opt_cse_local(fs_bblock *block, exec_list *aeb)
       }
 
       /* Kill all AEB entries that use the destination. */
-      int start_offset = inst->dst.reg_offset;
-      int end_offset = start_offset + inst->regs_written();
-
       foreach_list_safe(entry_node, aeb) {
 	 aeb_entry *entry = (aeb_entry *)entry_node;
 
 	 for (int i = 0; i < 3; i++) {
-	    if (entry->generator->src[i].file == inst->dst.file &&
-		entry->generator->src[i].reg == inst->dst.reg &&
-		entry->generator->src[i].reg_offset >= start_offset &&
-		entry->generator->src[i].reg_offset < end_offset) {
+            if (inst->overwrites_reg(entry->generator->src[i])) {
 	       entry->remove();
 	       ralloc_free(entry);
 	       break;