[PATCH 4/5] [GSOC] ref-filter: reduce unnecessary object_info comparisons

["ZheNing Hu via GitGitGadget" <gitgitgadget@gmail.com>]

From: ZheNing Hu <adlternative@gmail.com>

In populate_value() we use an empty struct object_info
compare with oi and oi_deref, which determine if we can
return early, this is actually very inefficient.

So add a need_get_object_info flag in global variables,
which used to indicate whether we need call get_object()
or we can return early.

So we only need to compare only one byte instead of comparing
the entire huge object_info struct.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Hariom Verma <hariom18599@gmail.com>
Signed-off-by: ZheNing Hu <adlternative@gmail.com>
---
 ref-filter.c | 34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/ref-filter.c b/ref-filter.c
index 7106d4c1c4c..35e221e7ec8 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -212,7 +212,7 @@ static struct used_atom {
 		char *head;
 	} u;
 } *used_atom;
-static int used_atom_cnt, need_tagged, need_symref;
+static int used_atom_cnt, need_tagged, need_symref, need_get_object_info;
 
 /*
  * Expand string, append it to strbuf *sb, then return error code ret.
@@ -318,10 +318,13 @@ static int objecttype_atom_parser(struct ref_format *format, struct used_atom *a
 {
 	if (arg)
 		return strbuf_addf_ret(err, -1, _("%%(objecttype) does not take arguments"));
-	if (*atom->name == '*')
+	if (*atom->name == '*') {
 		oi_deref.info.typep = &oi_deref.type;
-	else
+		need_get_object_info = 1;
+	} else {
 		oi.info.typep = &oi.type;
+		need_get_object_info = 1;
+	}
 	return 0;
 }
 
@@ -330,16 +333,23 @@ static int objectsize_atom_parser(struct ref_format *format, struct used_atom *a
 {
 	if (!arg) {
 		atom->u.objectsize.option = O_SIZE;
-		if (*atom->name == '*')
+		if (*atom->name == '*') {
 			oi_deref.info.sizep = &oi_deref.size;
-		else
+			need_get_object_info = 1;
+		} else {
 			oi.info.sizep = &oi.size;
+			need_get_object_info = 1;
+		}
 	} else if (!strcmp(arg, "disk")) {
 		atom->u.objectsize.option = O_SIZE_DISK;
-		if (*atom->name == '*')
+		if (*atom->name == '*') {
 			oi_deref.info.disk_sizep = &oi_deref.disk_size;
-		else
+			need_get_object_info = 1;
+		}
+		else {
 			oi.info.disk_sizep = &oi.disk_size;
+			need_get_object_info = 1;
+		}
 	} else
 		return strbuf_addf_ret(err, -1, _("unrecognized %%(objectsize) argument: %s"), arg);
 	return 0;
@@ -354,6 +364,7 @@ static int deltabase_atom_parser(struct ref_format *format, struct used_atom *at
 		oi_deref.info.delta_base_oid = &oi_deref.delta_base_oid;
 	else
 		oi.info.delta_base_oid = &oi.delta_base_oid;
+	need_get_object_info = 1;
 	return 0;
 }
 
@@ -720,6 +731,7 @@ static int parse_ref_filter_atom(struct ref_format *format,
 	used_atom[at].type = valid_atom[i].cmp_type;
 	used_atom[at].source = valid_atom[i].source;
 	if (used_atom[at].source == SOURCE_OBJ) {
+		need_get_object_info = 1;
 		if (*atom == '*')
 			oi_deref.info.contentp = &oi_deref.content;
 		else
@@ -1871,7 +1883,6 @@ static int populate_value(struct ref_array_item *ref, struct strbuf *err)
 {
 	struct object *obj;
 	int i;
-	struct object_info empty = OBJECT_INFO_INIT;
 
 	CALLOC_ARRAY(ref->value, used_atom_cnt);
 
@@ -2019,10 +2030,11 @@ static int populate_value(struct ref_array_item *ref, struct strbuf *err)
 					       oid_to_hex(&ref->objectname), ref->refname);
 	}
 
-	if (need_tagged)
+	if (need_tagged) {
 		oi.info.contentp = &oi.content;
-	if (!memcmp(&oi.info, &empty, sizeof(empty)) &&
-	    !memcmp(&oi_deref.info, &empty, sizeof(empty)))
+		need_get_object_info = 1;
+	}
+	if (!need_get_object_info)
 		return 0;
 
 
-- 
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