issue #30 Start implementing liveness analysis

CMakeLists.txt

@@ -42,6 +42,7 @@ set(SRCS
         src/dataflow_framework.c
         src/opt_unusedcode.c
         src/membuf.c
+        src/df_liveness.c
         )
 
 message("SOURCE dir is ${RaviCompiler_SOURCE_DIR}")

src/bitset.h

@@ -8,6 +8,9 @@
 #ifndef ravicomp_BITSET_H
 #define ravicomp_BITSET_H
 
+#include <stdint.h>
+#include <stdbool.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif

src/dataflow_framework.c

@@ -12,10 +12,6 @@
 
 DECLARE_ARRAY(node_array, struct node *);
 
-/**
- * The data flow framework is based on the implementation in MIR project.
- * https://github.com/vnmakarov/mir
- */
 struct dataflow_context {
 	struct graph *g;
 	struct node_array worklist;
@@ -69,6 +65,7 @@ void raviX_solve_dataflow(struct graph *g, bool forward_p,
 			int changed_p = iter == 0;
 			struct node *bb = addr[i];
 			struct node_list *nodes = forward_p ? raviX_predecessors(bb) : raviX_successors(bb);
+			// TODO should we pass the nodes array to the join function?
 			if (raviX_node_list_size(nodes) == 0)
 				join_function(ctx.userdata, raviX_node_index(bb), true);
 			else

src/dataflow_framework.h

@@ -11,7 +11,7 @@
 extern void raviX_solve_dataflow(
     struct graph *g,
     bool forward_p, /* Set to true for forward data flow */
-    int (*join_function)(void *userdata, nodeId_t, bool init), /* Join/Meet operator - init will be true when no successors/predecessors */
+    int (*join_function)(void *userdata, nodeId_t, bool init), /* Join/Meet operator - if init is true reset the bitsets */
     int (*transfer_function)(void *userdata, nodeId_t), /* transfer function */
     void *userdata);  /* pointer to user data, will be passed to join/transfer functions */
 

src/df_liveness.c

@@ -0,0 +1,99 @@
+/*
+ * Calculate variable liveness
+ * This will use the Dataflow Framework.
+ * Implementation inspired by one in MIR
+ */
+
+
+#include "bitset.h"
+#include "dataflow_framework.h"
+#include "linearizer.h"
+
+struct liveness_info {
+	nodeId_t node_id;
+	struct bitset_t in;
+	struct bitset_t out;
+	struct bitset_t use;
+	struct bitset_t def;
+};
+
+DECLARE_ARRAY(liveness_info_array, struct liveness_info *);
+
+struct liveness_data {
+	struct proc *proc;
+	struct liveness_info_array lives;
+};
+
+void init_liveness_data(struct proc *proc, struct liveness_data *liveness_data)
+{
+	memset(liveness_data, 0, sizeof(*liveness_data));
+	for (unsigned i = 0; i < proc->node_count; i++) {
+		struct liveness_info *liveness_info = (struct liveness_info *)calloc(1, sizeof(struct liveness_info));
+		liveness_info->node_id = i;
+		raviX_bitset_create(&liveness_info->use);
+		raviX_bitset_create(&liveness_info->def);
+		raviX_bitset_create(&liveness_info->in);
+		raviX_bitset_create(&liveness_info->out);
+		array_push(&liveness_data->lives, liveness_info);
+	}
+}
+
+void destroy_liveness_data(struct liveness_data *liveness_data)
+{
+	for (unsigned i = 0; i < liveness_data->lives.count; i++) {
+		raviX_bitset_create(&liveness_data->lives.data[i]->use);
+		raviX_bitset_create(&liveness_data->lives.data[i]->def);
+		raviX_bitset_create(&liveness_data->lives.data[i]->in);
+		raviX_bitset_create(&liveness_data->lives.data[i]->out);
+	}
+	array_clearmem(&liveness_data->lives);
+}
+
+static inline struct liveness_info *get_liveness_info(struct liveness_data *liveness_data, nodeId_t id)
+{
+	return liveness_data->lives.data[id];
+}
+
+/* Life analysis */
+static int live_join_func(void *userdata, nodeId_t id, bool init)
+{
+	struct liveness_data *liveness_data = (struct liveness_data *)userdata;
+	struct liveness_info *liveness_info = get_liveness_info(liveness_data, id);
+	if (init) {
+		raviX_bitset_clear(&liveness_info->in);
+		return 0;
+	} else {
+		struct node_list *successors = raviX_successors(raviX_graph_node(liveness_data->proc->cfg, id));
+		int changed = 0;
+		// out[n] = Union of in[s] where s in succ[n]
+		for (unsigned i = 0; i < raviX_node_list_size(successors); i++) {
+			nodeId_t succ_id = raviX_node_list_at(successors, i);
+			struct liveness_info *successor_liveness_info = get_liveness_info(liveness_data, succ_id);
+			changed |=
+			    raviX_bitset_ior(&liveness_info->out, &liveness_info->out, &successor_liveness_info->in);
+		}
+		return changed;
+	}
+}
+
+static int live_transfer_func(void *userdata, nodeId_t id)
+{
+	struct liveness_data *liveness_data = (struct liveness_data *)userdata;
+	struct liveness_info *liveness_info = get_liveness_info(liveness_data, id);
+	// out[n] = use[n] U (out[n] - def[n])
+	// In bitset terms out[n] = use[n] | (out[n] & ~def[n])
+	return raviX_bitset_ior_and_compl(&liveness_info->in, &liveness_info->use, &liveness_info->out,
+					  &liveness_info->def);
+}
+
+// TODO
+
+// Compute use/def sets of each node
+// If a reg appears as the target of an instruction that's a def
+// If a reg is used as operand then its a use
+// Need to handle ranges / var args too
+// Or should we restrict analysis to certain types of regs?
+
+// Right now we have disjoint sets for temps / locals  - to do this efficiently we need a merged set of regs for each proc
+// Liveness analysis is a backward data flow problem
+// see calculate_func_cfg_live_info  in mir_genc.c