intel/compiler: Move register pressure calculation into IR analysis object

This defines a new BRW_ANALYSIS object which wraps the register
pressure computation code along with its result.  For the rationale
see the previous commits converting the liveness and dominance
analysis passes to the IR analysis framework.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4012>

src/intel/compiler/brw_fs.h

@@ -39,7 +39,34 @@ namespace {
    struct acp_entry;
 }
 
+class fs_visitor;
+
 namespace brw {
+   /**
+    * Register pressure analysis of a shader.  Estimates how many registers
+    * are live at any point of the program in GRF units.
+    */
+   struct register_pressure {
+      register_pressure(const fs_visitor *v);
+      ~register_pressure();
+
+      analysis_dependency_class
+      dependency_class() const
+      {
+         return (DEPENDENCY_INSTRUCTION_IDENTITY |
+                 DEPENDENCY_INSTRUCTION_DATA_FLOW |
+                 DEPENDENCY_VARIABLES);
+      }
+
+      bool
+      validate(const fs_visitor *) const
+      {
+         /* FINISHME */
+         return true;
+      }
+
+      unsigned *regs_live_at_ip;
+   };
 }
 
 struct brw_gs_compile;
@@ -126,7 +153,6 @@ public:
                       unsigned *out_pull_index);
    void lower_constant_loads();
    virtual void invalidate_analysis(brw::analysis_dependency_class c);
-   void calculate_register_pressure();
    void validate();
    bool opt_algebraic();
    bool opt_redundant_discard_jumps();
@@ -322,8 +348,8 @@ public:
 
    BRW_ANALYSIS(live_analysis, brw::fs_live_variables,
                 backend_shader *) live_analysis;
-
-   int *regs_live_at_ip;
+   BRW_ANALYSIS(regpressure_analysis, brw::register_pressure,
+                fs_visitor *) regpressure_analysis;
 
    /** Number of uniform variable components visited. */
    unsigned uniforms;