[PATCH] LCM: Export 2 helpful functions as global for VSETVL PASS use in RISC-V backend

[Juzhe-Zhong <juzhe.zhong@rivai.ai>]

This patch exports 'compute_antinout_edge' and 'compute_earliest' as global scope
which is going to be used in VSETVL PASS of RISC-V backend.

The demand fusion is the fusion of VSETVL information to emit VSETVL which dominate and pre-config for most
of the RVV instructions in order to elide redundant VSETVLs.

For exmaple:

for
 for
  for
    if (cond}
      VSETVL demand 1: SEW/LMUL = 16 and TU policy
    else
      VSETVL demand 2: SEW = 32

VSETVL pass should be able to fuse demand 1 and demand 2 into new demand: SEW = 32, LMUL = M2, TU policy.
Then emit such VSETVL at the outmost of the for loop to get the most optimal codegen and run-time execution.

Currenty the VSETVL PASS Phase 3 (demand fusion) is really messy and un-reliable as well as un-maintainable.
And, I recently read dragon book and morgan's book again, I found there "earliest" can allow us to do the
demand fusion in a very reliable and optimal way.

So, this patch exports these 2 functions which are very helpful for VSETVL pass.

gcc/ChangeLog:

	* lcm.cc (compute_antinout_edge): Export as global use.
	(compute_earliest): Ditto.
	(compute_rev_insert_delete): Ditto.
	* lcm.h (compute_antinout_edge): Ditto.
	(compute_earliest): Ditto.

---
 gcc/lcm.cc | 7 ++-----
 gcc/lcm.h  | 3 +++
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/gcc/lcm.cc b/gcc/lcm.cc
index 94a3ed43aea..03421e490e4 100644
--- a/gcc/lcm.cc
+++ b/gcc/lcm.cc
@@ -56,9 +56,6 @@ along with GCC; see the file COPYING3.  If not see
 #include "lcm.h"
 
 /* Edge based LCM routines.  */
-static void compute_antinout_edge (sbitmap *, sbitmap *, sbitmap *, sbitmap *);
-static void compute_earliest (struct edge_list *, int, sbitmap *, sbitmap *,
-			      sbitmap *, sbitmap *, sbitmap *);
 static void compute_laterin (struct edge_list *, sbitmap *, sbitmap *,
 			     sbitmap *, sbitmap *);
 static void compute_insert_delete (struct edge_list *edge_list, sbitmap *,
@@ -79,7 +76,7 @@ static void compute_rev_insert_delete (struct edge_list *edge_list, sbitmap *,
    This is done based on the flow graph, and not on the pred-succ lists.
    Other than that, its pretty much identical to compute_antinout.  */
 
-static void
+void
 compute_antinout_edge (sbitmap *antloc, sbitmap *transp, sbitmap *antin,
 		       sbitmap *antout)
 {
@@ -170,7 +167,7 @@ compute_antinout_edge (sbitmap *antloc, sbitmap *transp, sbitmap *antin,
 
 /* Compute the earliest vector for edge based lcm.  */
 
-static void
+void
 compute_earliest (struct edge_list *edge_list, int n_exprs, sbitmap *antin,
 		  sbitmap *antout, sbitmap *avout, sbitmap *kill,
 		  sbitmap *earliest)
diff --git a/gcc/lcm.h b/gcc/lcm.h
index e08339352e0..7145d6fc46d 100644
--- a/gcc/lcm.h
+++ b/gcc/lcm.h
@@ -31,4 +31,7 @@ extern struct edge_list *pre_edge_rev_lcm (int, sbitmap *,
 					   sbitmap *, sbitmap *,
 					   sbitmap *, sbitmap **,
 					   sbitmap **);
+extern void compute_antinout_edge (sbitmap *, sbitmap *, sbitmap *, sbitmap *);
+extern void compute_earliest (struct edge_list *, int, sbitmap *, sbitmap *,
+			      sbitmap *, sbitmap *, sbitmap *);
 #endif /* GCC_LCM_H */
-- 
2.36.3