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Make graphds_scc pass the node order back to callers

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As a side-effect, graphds_scc constructs a vector in which all
nodes in an SCC are listed consecutively.  This can be useful
information, so that the patch adds an optional pass-back parameter
for it.  The interface is similar to the one for graphds_dfs.

gcc/
	* graphds.cc (graphds_scc): Add a pass-back parameter for the
	final node order.
	* graphds.h (graphds_scc): Update prototype accordingly.
This commit is contained in:
Richard Sandiford 2022-08-30 15:43:46 +01:00
parent 5551501e84
commit 2bac880a19
2 changed files with 12 additions and 4 deletions
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13
gcc/graphds.cc
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@ -281,7 +281,14 @@ graphds_dfs (struct graph *g, int *qs, int nq, vec<int> *qt,
numbers assigned by the previous pass. If SUBGRAPH is not NULL, it
specifies the subgraph of G whose strongly connected components we want
to determine. If SKIP_EDGE_P is not NULL, it points to a callback function.
Edge E will be skipped if callback function returns true.
Edge E will be skipped if callback function returns true. If SCC_GROUPING
is not null, the nodes will be added to it in the following order:
- If SCC A is a direct or indirect predecessor of SCC B in the SCC dag,
A's nodes come before B's nodes.
- All of an SCC's nodes are listed consecutively, although the order
of the nodes within an SCC is not really meaningful.
After running this function, v->component is the number of the strongly
connected component for each vertex of G. Returns the number of the
@ -289,7 +296,7 @@ graphds_dfs (struct graph *g, int *qs, int nq, vec<int> *qt,
int
graphds_scc (struct graph *g, bitmap subgraph,
skip_edge_callback skip_edge_p)
skip_edge_callback skip_edge_p, vec<int> *scc_grouping)
{
int *queue = XNEWVEC (int, g->n_vertices);
vec<int> postorder = vNULL;
@ -317,7 +324,7 @@ graphds_scc (struct graph *g, bitmap subgraph,
for (i = 0; i < nq; i++)
queue[i] = postorder[nq - i - 1];
comp = graphds_dfs (g, queue, nq, NULL, true, subgraph, skip_edge_p);
comp = graphds_dfs (g, queue, nq, scc_grouping, true, subgraph, skip_edge_p);
free (queue);
postorder.release ();

3
gcc/graphds.h
View file

@ -58,7 +58,8 @@ void identify_vertices (struct graph *, int, int);
typedef bool (*skip_edge_callback) (struct graph_edge *);
int graphds_dfs (struct graph *, int *, int,
vec<int> *, bool, bitmap, skip_edge_callback = NULL);
int graphds_scc (struct graph *, bitmap, skip_edge_callback = NULL);
int graphds_scc (struct graph *, bitmap, skip_edge_callback = NULL,
vec<int> * = NULL);
void graphds_domtree (struct graph *, int, int *, int *, int *);
typedef void (*graphds_edge_callback) (struct graph *,
struct graph_edge *, void *);