aco: Add get_temp_reg_changes helper

Similar to get_live_changes, but considers live temporary registers
as well.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29730>

src/amd/compiler/aco_ir.h

@@ -2318,6 +2318,7 @@ int get_op_fixed_to_def(Instruction* instr);
 /* utilities for dealing with register demand */
 RegisterDemand get_live_changes(Instruction* instr);
 RegisterDemand get_temp_registers(Instruction* instr);
+RegisterDemand get_temp_reg_changes(Instruction* instr);
 
 /* adjust num_waves for workgroup size and LDS limits */
 uint16_t max_suitable_waves(Program* program, uint16_t waves);

src/amd/compiler/aco_live_var_analysis.cpp

@@ -55,6 +55,23 @@ get_temp_registers(Instruction* instr)
    return demand_after;
 }
 
+RegisterDemand get_temp_reg_changes(Instruction* instr)
+{
+   RegisterDemand available_def_space;
+
+   for (Definition def : instr->definitions) {
+      if (def.isTemp())
+         available_def_space += def.getTemp();
+   }
+
+   for (Operand op : instr->operands) {
+      if (op.isFirstKillBeforeDef() || op.isCopyKill())
+         available_def_space -= op.getTemp();
+   }
+
+   return available_def_space;
+}
+
 namespace {
 
 struct live_ctx {