[qfcc] Lots of flow analysis docs
And some function shuffling for grouping. I'm not satisfied with the docs, but they're a lot more helpful than they were.
This commit is contained in:
Bill Currie
parent
809c103fd1
commit
e4c87091a3
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@ -57,11 +57,11 @@
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#include "symtab.h"
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#include "type.h"
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static flowvar_t *vars_freelist;
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static flowloop_t *loops_freelist;
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static flownode_t *nodes_freelist;
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static flowgraph_t *graphs_freelist;
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/// \addtogroup qfcc_flow
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///@{
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/** Static operand definitions for the ever present return and parameter slots.
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*/
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static struct {
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const char *name;
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operand_t op;
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@ -78,6 +78,17 @@ static struct {
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};
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static const int num_flow_params = sizeof(flow_params)/sizeof(flow_params[0]);
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/** \name Flow analysis memory management */
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///@{
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static flowvar_t *vars_freelist; ///< flowvar pool
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static flowloop_t *loops_freelist; ///< flow loop pool
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static flownode_t *nodes_freelist; ///< flow node pool
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static flowgraph_t *graphs_freelist; ///< flow graph pool
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/** Allocate a new flow var.
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*
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* The var's use and define sets are initialized to empty.
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*/
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static flowvar_t *
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new_flowvar (void)
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{
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@ -88,6 +99,10 @@ new_flowvar (void)
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return var;
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}
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/** Allocate a new flow loop.
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*
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* The loop's nodes set is initialized to the empty set.
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*/
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static flowloop_t *
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new_loop (void)
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{
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@ -97,6 +112,8 @@ new_loop (void)
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return loop;
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}
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/** Free a flow loop and its nodes set.
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*/
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static void
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delete_loop (flowloop_t *loop)
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{
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@ -104,6 +121,10 @@ delete_loop (flowloop_t *loop)
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FREE (loops, loop);
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}
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/** Allocate a new flow node.
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*
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* The node is completely empty.
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*/
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static flownode_t *
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new_node (void)
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{
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@ -112,6 +133,10 @@ new_node (void)
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return node;
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}
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/** Free a flow node and its resources.
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*
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* \bug not global_vars or the vars and defs sets?
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*/
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static void
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delete_node (flownode_t *node)
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{
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@ -126,6 +151,10 @@ delete_node (flownode_t *node)
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FREE (nodes, node);
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}
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/** Allocate a new flow graph.
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*
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* The graph is completely empty.
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*/
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static flowgraph_t *
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new_graph (void)
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{
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@ -134,6 +163,10 @@ new_graph (void)
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return graph;
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}
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/** Return a flow graph and its resources to the pools.
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*
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* \bug except loops?
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*/
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static void __attribute__((unused))
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delete_graph (flowgraph_t *graph)
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{
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@ -152,7 +185,77 @@ delete_graph (flowgraph_t *graph)
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free (graph->depth_first);
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FREE (graphs, graph);
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}
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///@}
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/** \name Flowvar classification */
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///@{
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/** Check if the flowvar refers to a global variable.
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*
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* For the flowvar to refer to a global variable, the flowvar's operand
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* must be a def operand (but the def itself may be an alias of the real def)
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* and the rel def must not have its def_t::local flag set. This means that
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* function-scope static variables are not considered local (ie, only
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* non-static function-scope variables and function parameters are considered
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* local (temp vars are local too, but are not represented by \a op_def)).
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*/
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static int
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flowvar_is_global (flowvar_t *var)
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{
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def_t *def;
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if (var->op->op_type != op_def)
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return 0;
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def = var->op->o.def;
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if (def->alias)
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def = def->alias;
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if (def->local)
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return 0;
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return 1;
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}
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/** Check if the flowvar refers to a function parameter.
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*
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* For the flowvar to refer to a function parameter, the flowvar's operand
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* must be a def operand (but the def itself may be an alias of the real def)
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* and the rel def must have both its def_t::local and def_t::param flags set.
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*
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* Temp vars are are not represented by op_def, so no mistake can be made.
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*/
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static int
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flowvar_is_param (flowvar_t *var)
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{
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def_t *def;
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if (var->op->op_type != op_def)
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return 0;
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def = var->op->o.def;
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if (def->alias)
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def = def->alias;
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if (!def->local)
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return 0;
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if (!def->param)
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return 0;
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return 1;
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}
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/** Check if the flowvar refers to a function parameter.
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*
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* As this is simply "neither global nor pamam", all other flowvars are
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* considered local, in particular actual non-staic function scope variables
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* and temp vars.
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*/
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static int
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flowvar_is_local (flowvar_t *var)
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{
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return !(flowvar_is_global (var) || flowvar_is_param (var));
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}
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///@}
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/** Extract the def from a def or temp flowvar.
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*
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* It is an error for the operand referenced by the flowvar to be anything
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* other than a real def or temp.
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*/
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static __attribute__((pure)) def_t *
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flowvar_get_def (flowvar_t *var)
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{
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@ -173,43 +276,13 @@ flowvar_get_def (flowvar_t *var)
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return 0;
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}
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static int
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flowvar_is_global (flowvar_t *var)
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{
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def_t *def;
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if (var->op->op_type != op_def)
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return 0;
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def = var->op->o.def;
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if (def->alias)
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def = def->alias;
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if (def->local)
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return 0;
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return 1;
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}
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static int
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flowvar_is_param (flowvar_t *var)
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{
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def_t *def;
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if (var->op->op_type != op_def)
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return 0;
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def = var->op->o.def;
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if (def->alias)
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def = def->alias;
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if (!def->local)
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return 0;
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if (!def->param)
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return 0;
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return 1;
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}
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static int
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flowvar_is_local (flowvar_t *var)
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{
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return !(flowvar_is_global (var) || flowvar_is_param (var));
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}
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/** Get a def or temp var operand's flowvar.
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*
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* Other operand types never have a flowvar.
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*
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* If the operand does not yet have a flowvar, one is created and assigned
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* to the operand.
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*/
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flowvar_t *
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flow_get_var (operand_t *op)
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{
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@ -229,6 +302,12 @@ flow_get_var (operand_t *op)
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return 0;
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}
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/** Indicate whether the operand should be counted.
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*
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* If the operand is a def or temp var operand, and it has not already been
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* counted, then it is counted, otherwise it is not.
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* \return 1 if the operand should be counted, 0 if not
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*/
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static int
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count_operand (operand_t *op)
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{
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@ -240,14 +319,15 @@ count_operand (operand_t *op)
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return 0;
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var = flow_get_var (op);
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// flowvars are initialized with number == 0, and any global flowvar
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// used by a function will always have a number >= 0 after flow analysis,
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// and local flowvars will always be 0 before flow analysis, so use -1
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// to indicate the variable has been counted.
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//
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// Also, since this is the beginning of flow analysis for this function,
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// ensure the define/use sets for global vars are empty. However, as
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// checking if a var is global is too much trouble, just clear them all.
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/** Flowvars are initialized with number == 0, and any global flowvar
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* used by a function will always have a number >= 0 after flow analysis,
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* and local flowvars will always be 0 before flow analysis, so use -1
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* to indicate the variable has been counted.
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*
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* Also, since this is the beginning of flow analysis for this function,
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* ensure the define/use sets for global vars are empty. However, since
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* checking if a var is global is too much trouble, just clear them all.
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*/
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if (var && var->number != -1) {
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set_empty (var->use);
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set_empty (var->define);
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@ -257,6 +337,22 @@ count_operand (operand_t *op)
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return 0;
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}
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/** Allocate flow analysis pseudo address space to a temporary variable.
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*
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* If the operand already has an address allocated (flowvar_t::flowaddr is
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* not 0), then the already allocated address is returned.
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*
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* If the operand refers to an alias, the alias chain is followed to the
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* actual temp var operand and the real temp var is allocated space if it
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* has not allready been alloced.
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*
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* The operand is given the address of the real temp var operand plus whatever
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* offset the operand has.
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*
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* Real temp var operands must have a zero offset.
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*
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* The operand address is set in \a op and returned.
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*/
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static int
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get_temp_address (function_t *func, operand_t *op)
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{
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@ -278,6 +374,8 @@ get_temp_address (function_t *func, operand_t *op)
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return op->o.tempop.flowaddr;
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}
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/** Add an operand's flowvar to the function's list of variables.
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*/
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static void
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add_operand (function_t *func, operand_t *op)
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{
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@ -289,8 +387,15 @@ add_operand (function_t *func, operand_t *op)
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return;
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var = flow_get_var (op);
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// If the flowvar number is still -1, then the flowvar has not yet been
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// added to the list of variables referenced by the function.
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/** If the flowvar number is still -1, then the flowvar has not yet been
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* added to the list of variables referenced by the function.
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*
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* The flowvar's flowvar_t::number is set to its index in the function's
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* list of flowvars.
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*
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* Also, temp and local flowvars are assigned addresses from the flow
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* analysys pseudo address space so partial accesses can be analyzed.
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*/
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if (var && var->number == -1) {
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var->number = func->num_vars++;
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var->op = op;
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@ -303,6 +408,8 @@ add_operand (function_t *func, operand_t *op)
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}
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}
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/** Create symbols and defs for params/return if not already available.
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*/
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static symbol_t *
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param_symbol (const char *name)
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{
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@ -313,6 +420,15 @@ param_symbol (const char *name)
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return sym;
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}
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/** Build an array of all the statements in a function.
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The array exists so statements can be referenced by number and thus used
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in sets.
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The statement references in the array (function_t::statements) are in the
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same order as they are within the statement blocks (function_t::sblock)
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and with the blocks in the same order as the linked list of blocks.
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*/
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static void
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flow_build_statements (function_t *func)
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{
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@ -335,6 +451,48 @@ flow_build_statements (function_t *func)
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}
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}
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/** Build an array of all the variables used by a function
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*
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* The array exists so variables can be referenced by number and thus used
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* in sets. However, because larger variables may be aliased by smaller types,
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* their representation is more complicated.
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*
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* # Local variable representation
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* Defined local vars add their address in local space to the number of
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* statements in the function. Thus their flow analysis address in in the
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* range:
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*
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* ([num_statements ... num_statements+localsize])
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*
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* with a set element in flowvar_t::define for each word used by the var.
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* That is, single word types (int, float, pointer, etc) have one element,
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* doubles have two adjacant elements, and vectors and quaternions have
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* three and four elements respectively (also adjacant). Structural types
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* (struct, union, array) have as many adjacant elements as their size
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* dictates.
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*
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* Temporary vars are pseudo allocated and their addresses are added as
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* for normal local vars.
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*
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* Note, however, that flowvar_t::define also includes real function
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* statements that assign to the variable.
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*
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* # Pseudo Address Space
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* Temporary variables are _effectively_ local variables and thus will
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* be treated as such by the analizer in that their addresses and sizes
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* will be used to determine which and how many set elements to use.
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*
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* However, at this stage, temporary variables do not have any address
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* space assigned to them because their lifetimes are generally limited
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* to a few statements and the memory used for the temp vars may be
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* recycled. Thus, give temp vars a pseudo address space just past the
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* address space used for source-defined local variables. As each temp
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* var is added to the analyzer, get_temp_address() assigns the temp var
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* an address using function_t::tmpaddr as a starting point.
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*
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* add_operand() takes care of setting flowvar_t::flowaddr for both locals
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* and temps.
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*/
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static void
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flow_build_vars (function_t *func)
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{
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@ -371,6 +529,7 @@ flow_build_vars (function_t *func)
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// set up pseudo address space for temp vars so accessing tmp vars
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// though aliases analyses correctly
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func->tmpaddr = func->num_statements + func->symtab->space->size;
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func->num_vars = 0; // incremented by add_operand
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// first, add .return and .param_[0-7] as they are always needed
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for (i = 0; i < num_flow_params; i++)
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@ -399,15 +558,8 @@ flow_build_vars (function_t *func)
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if (flowvar_is_global (func->vars[i]))
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set_add (func->global_vars, i);
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}
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// create dummy defs for local vars
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// defined local vars add their address in local space to the number of
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// statements in the function:
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// ([num_statements ... num_statements+localsize])
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// with a set element for each def used in the local space
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//
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// temporary vars are pseudo allocated and their addresses are added as for
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// locals
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// add_operand takes care of setting flowaddr for both locals and temps
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// Put the local varibals in their place (set var->defined to the addresses
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// spanned by the var)
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for (i = 0; i < func->num_vars; i++) {
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int j;
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@ -424,6 +576,8 @@ flow_build_vars (function_t *func)
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set_delete (stdef);
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}
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/** Add the tempop's spanned addresses to the kill set
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*/
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static int
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flow_tempop_kill_aliases_visit (tempop_t *tempop, void *_kill)
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{
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@ -435,6 +589,8 @@ flow_tempop_kill_aliases_visit (tempop_t *tempop, void *_kill)
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return 0;
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}
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/** Add the def's spanned addresses to the kill set
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*/
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static int
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flow_def_kill_aliases_visit (def_t *def, void *_kill)
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{
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@ -446,6 +602,13 @@ flow_def_kill_aliases_visit (def_t *def, void *_kill)
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return 0;
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}
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/** Add the flowvar's spanned addresses to the kill set
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*
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* If the flowvar refers to an alias, then the real def/tempop and any
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* overlapping aliases are aslo killed.
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*
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* However, other aliases cannot kill anything in the uninitialized set.
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*/
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static void
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flow_kill_aliases (set_t *kill, flowvar_t *var, const set_t *uninit)
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{
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@ -455,6 +618,7 @@ flow_kill_aliases (set_t *kill, flowvar_t *var, const set_t *uninit)
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set_union (kill, var->define);
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op = var->op;
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tmp = set_new ();
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// collect the kill sets from any aliases
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if (op->op_type == op_temp) {
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tempop_visit_all (&op->o.tempop, 1, flow_tempop_kill_aliases_visit,
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tmp);
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@ -467,6 +631,8 @@ flow_kill_aliases (set_t *kill, flowvar_t *var, const set_t *uninit)
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set_union (kill, tmp);
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}
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/** Compute reaching defs
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*/
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static void
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flow_reaching_defs (flowgraph_t *graph)
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{
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@ -484,15 +650,37 @@ flow_reaching_defs (flowgraph_t *graph)
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flowvar_t *var;
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// First, create out for the entry dummy node using fake statement numbers.
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//\f[ \bigcup\limits_{i=1}^{\infty} F_{i} \f]
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//\f[ \bigcap\limits_{i=1}^{\infty} F_{i} \f]
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||||
/** The dummy entry node reaching defs \a out set is initialized to:
|
||||
* \f[ out_{reaching}=[\bigcup\limits_{v \in \{locals\}} define_{v}]
|
||||
* \setminus \{statements\} \f]
|
||||
* where {\a locals} is the set of local def and tempop flowvars (does
|
||||
* not include parameters), \a define is the set of addresses spanned
|
||||
* by the flowvar (see flow_build_vars()) (XXX along with statement
|
||||
* gens), and {\a statements} is the set of all statements in the
|
||||
* function (ensures the \a out set does not include any initializers in
|
||||
* the code nodes).
|
||||
*
|
||||
* All other entry node sets are initialized to empty.
|
||||
*/
|
||||
// kill represents the set of all statements in the function
|
||||
kill = set_new ();
|
||||
for (i = 0; i < graph->func->num_statements; i++)
|
||||
set_add (kill, i);
|
||||
// uninit
|
||||
uninit = set_new ();
|
||||
for (i = 0; i < graph->func->num_vars; i++) {
|
||||
var = graph->func->vars[i];
|
||||
set_union (uninit, var->define);// do not want alias handling here
|
||||
}
|
||||
/** Any possible gens from the function code are removed from the
|
||||
* \a uninit set (which becomes the \a out set of the entry node's
|
||||
* reaching defs) in order to prevent them leaking into the real nodes.
|
||||
*/
|
||||
set_difference (uninit, kill); // remove any gens from the function
|
||||
// initialize the reaching defs sets in the entry node
|
||||
graph->nodes[graph->num_nodes]->reaching_defs.out = uninit;
|
||||
graph->nodes[graph->num_nodes]->reaching_defs.in = set_new ();
|
||||
graph->nodes[graph->num_nodes]->reaching_defs.gen = set_new ();
|
||||
|
|
@ -555,6 +743,8 @@ flow_reaching_defs (flowgraph_t *graph)
|
|||
set_delete (stkill);
|
||||
}
|
||||
|
||||
/** Update the node's \a use set from the statement's \a use set
|
||||
*/
|
||||
static void
|
||||
live_set_use (set_t *stuse, set_t *use, set_t *def)
|
||||
{
|
||||
|
|
@ -563,6 +753,8 @@ live_set_use (set_t *stuse, set_t *use, set_t *def)
|
|||
set_union (use, stuse);
|
||||
}
|
||||
|
||||
/** Update the node's \a def set from the statement's \a def set
|
||||
*/
|
||||
static void
|
||||
live_set_def (set_t *stdef, set_t *use, set_t *def)
|
||||
{
|
||||
|
|
@ -1240,6 +1432,35 @@ flow_make_node (sblock_t *sblock, int id, function_t *func)
|
|||
return node;
|
||||
}
|
||||
|
||||
/** Build the flow graph for the function.
|
||||
*
|
||||
* In addition to the nodes create by the statement blocks, there are two
|
||||
* dummy blocks:
|
||||
*
|
||||
* \dot
|
||||
* digraph flow_build_graph {
|
||||
* layout = dot; rankdir = TB; compound =true; nodesp = 1.0;
|
||||
* dummy_entry [shape=box,label="entry"];
|
||||
* sblock0 [label="code"]; sblock1 [label="code"];
|
||||
* sblock2 [label="code"]; sblock3 [label="code"];
|
||||
* dummy_exit [shape=box,label="exit"];
|
||||
* dummy_entry -> sblock0; sblock0 -> sblock1;
|
||||
* sblock1 -> sblock2; sblock2 -> sblock1;
|
||||
* sblock2 -> dummy_exit; sblock1 -> sblock3;
|
||||
* sblock3 -> dummy_exit;
|
||||
* }
|
||||
* \enddot
|
||||
*
|
||||
* The entry block is used for detecting use of uninitialized local variables
|
||||
* and the exit block is used for ensuring global variables are treated as
|
||||
* live at function exit.
|
||||
*
|
||||
* The exit block, which also is empty of statements, has its live vars
|
||||
* \a use set initilized to the set of global defs, which are simply numbered
|
||||
* by their index in the functions list of flowvars. All other exit node sets
|
||||
* are initialized to empty.
|
||||
* \f[ use_{live}=globals \f]
|
||||
*/
|
||||
static flowgraph_t *
|
||||
flow_build_graph (function_t *func)
|
||||
{
|
||||
|
|
@ -1303,3 +1524,5 @@ flow_data_flow (function_t *func)
|
|||
flow_cleanup_dags (graph);
|
||||
func->sblock = flow_generate (graph);
|
||||
}
|
||||
|
||||
///@}
|
||||
|
|
|
|||
Loading…
Reference in New Issue