The following patch makes sure to clear DECL_CHAIN of gimple_bind_vars
once we dissolve that (but makes sure to preserve the BLOCK_VARS tail).
This should allow better GC in the face of remove-unused-locals eventually
removing the last reference to a decl (and not keep it live via DECL_CHAIN
of some others).
I ran into the /* Ugh */ comment during libsubc++ build; rather than
trying to nail that down I papered over it ...
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
Richard.
2016-10-06 Richard Biener <rguent...@suse.de>
* gimple-low.c (lower_gimple_bind): Clear DECL_CHAIN of
vars in gimple_bind_vars but not in BLOCK_VARS.
Index: gcc/gimple-low.c
===================================================================
--- gcc/gimple-low.c (revision 240831)
+++ gcc/gimple-low.c (working copy)
@@ -416,6 +416,23 @@ lower_gimple_bind (gimple_stmt_iterator
}
record_vars (gimple_bind_vars (stmt));
+
+ /* Scrap DECL_CHAIN up to BLOCK_VARS to ease GC after we no longer
+ need gimple_bind_vars. */
+ tree next;
+ tree end = NULL_TREE;
+ if (gimple_bind_block (stmt))
+ end = BLOCK_VARS (gimple_bind_block (stmt));
+ for (tree var = gimple_bind_vars (stmt); var != end; var = next)
+ {
+ /* Ugh, something is violating the constraint that BLOCK_VARS
+ is a sub-chain of gimple_bind_vars. */
+ if (! var)
+ break;
+ next = DECL_CHAIN (var);
+ DECL_CHAIN (var) = NULL_TREE;
+ }
+
lower_sequence (gimple_bind_body_ptr (stmt), data);
if (new_block)
