While experimenting with some allocation changes I noticed that
df_insn_rescan frees a df_insn_info and implicitly requires
alloc-pool to give back the same data on reallocation:
bool the_same = df_insn_refs_verify (&collection_rec, bb, insn, false);
/* If there's no change, return false. */
if (the_same)
{
df_free_collection_rec (&collection_rec);
if (dump_file)
fprintf (dump_file, "verify found no changes in insn with uid =
%d.\n", uid);
return false;
}
if (dump_file)
fprintf (dump_file, "rescanning insn with uid = %d.\n", uid);
/* There's change - we need to delete the existing info.
Since the insn isn't moved, we can salvage its LUID. */
luid = DF_INSN_LUID (insn);
df_insn_info_delete (uid);
df_insn_create_insn_record (insn);
DF_INSN_LUID (insn) = luid;
We build up in collection_rec the list of references that INSN should
have, then exit early if the df info already matches. Otherwise we
tear down the old df_insn_info, allocate a new one, and copy the
references in collection_rec to it. The problem is that the references
in collection_rec refer to the old (freed) df_insn_info, so things break
if alloc pool gives back a different address.
The patch avoids the unnecessary free and reallocation. In principle
it should also be a slight compile-time optimisation, but (as expected)
the difference is far too small to be measurable.
Tested on x86_64-linux-gnu. OK to install?
Thanks,
Richard
gcc/
* df-scan.c (df_insn_info_init_fields): New function, split out
from...
(df_insn_create_insn_record): ...here.
(df_insn_info_free_fields): New function, split out from...
(df_insn_info_delete): ...here.
(df_insn_rescan): Use the new functions instead of freeing and
reallocating the df_insn_info.
diff --git a/gcc/df-scan.c b/gcc/df-scan.c
index 93c2eae..259c959 100644
--- a/gcc/df-scan.c
+++ b/gcc/df-scan.c
@@ -809,6 +809,14 @@ df_reg_chain_unlink (df_ref ref)
df_free_ref (ref);
}
+/* Initialize INSN_INFO to describe INSN. */
+
+static void
+df_insn_info_init_fields (df_insn_info *insn_info, rtx_insn *insn)
+{
+ memset (insn_info, 0, sizeof (struct df_insn_info));
+ insn_info->insn = insn;
+}
/* Create the insn record for INSN. If there was one there, zero it
out. */
@@ -827,8 +835,7 @@ df_insn_create_insn_record (rtx_insn *insn)
insn_rec = problem_data->insn_pool->allocate ();
DF_INSN_INFO_SET (insn, insn_rec);
}
- memset (insn_rec, 0, sizeof (struct df_insn_info));
- insn_rec->insn = insn;
+ df_insn_info_init_fields (insn_rec, insn);
return insn_rec;
}
@@ -876,6 +883,29 @@ df_mw_hardreg_chain_delete (struct df_mw_hardreg *hardregs)
}
}
+/* Remove the contents of INSN_INFO (but don't free INSN_INFO itself). */
+
+static void
+df_insn_info_free_fields (df_insn_info *insn_info)
+{
+ /* In general, notes do not have the insn_info fields
+ initialized. However, combine deletes insns by changing them
+ to notes. How clever. So we cannot just check if it is a
+ valid insn before short circuiting this code, we need to see
+ if we actually initialized it. */
+ df_mw_hardreg_chain_delete (insn_info->mw_hardregs);
+
+ if (df_chain)
+ {
+ df_ref_chain_delete_du_chain (insn_info->defs);
+ df_ref_chain_delete_du_chain (insn_info->uses);
+ df_ref_chain_delete_du_chain (insn_info->eq_uses);
+ }
+
+ df_ref_chain_delete (insn_info->defs);
+ df_ref_chain_delete (insn_info->uses);
+ df_ref_chain_delete (insn_info->eq_uses);
+}
/* Delete all of the refs information from the insn with UID.
Internal helper for df_insn_delete, df_insn_rescan, and other
@@ -895,24 +925,7 @@ df_insn_info_delete (unsigned int uid)
struct df_scan_problem_data *problem_data
= (struct df_scan_problem_data *) df_scan->problem_data;
- /* In general, notes do not have the insn_info fields
- initialized. However, combine deletes insns by changing them
- to notes. How clever. So we cannot just check if it is a
- valid insn before short circuiting this code, we need to see
- if we actually initialized it. */
- df_mw_hardreg_chain_delete (insn_info->mw_hardregs);
-
- if (df_chain)
- {
- df_ref_chain_delete_du_chain (insn_info->defs);
- df_ref_chain_delete_du_chain (insn_info->uses);
- df_ref_chain_delete_du_chain (insn_info->eq_uses);
- }
-
- df_ref_chain_delete (insn_info->defs);
- df_ref_chain_delete (insn_info->uses);
- df_ref_chain_delete (insn_info->eq_uses);
-
+ df_insn_info_free_fields (insn_info);
problem_data->insn_pool->remove (insn_info);
DF_INSN_UID_SET (uid, NULL);
}
@@ -1075,8 +1088,8 @@ df_insn_rescan (rtx_insn *insn)
/* There's change - we need to delete the existing info.
Since the insn isn't moved, we can salvage its LUID. */
luid = DF_INSN_LUID (insn);
- df_insn_info_delete (uid);
- df_insn_create_insn_record (insn);
+ df_insn_info_free_fields (insn_info);
+ df_insn_info_init_fields (insn_info, insn);
DF_INSN_LUID (insn) = luid;
}
else
