[PATCH v4 1/7] merge-ort: resolve paths early when we have sufficient information

From: Elijah Newren via GitGitGadget <gitgitgadget@gmail.com>
Date: Jul 21, 2021, 04:23 UTC
Message-ID: <7fdfeb159d0125cce980e63bcc1415144b91e486.1626841444.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.988.v4.git.1626841444.gitgitgadget@gmail.com>

From: Elijah Newren <newren@gmail.com>

When there are no directories involved at a given path, and all three sides have a file at that path, and two of the three sides of history match, we can immediately resolve the merge of that path in collect_merge_info() and do not need to wait until process_entries().

This is actually a very minor improvement: half the time when I run it, I see an improvement; the other half a slowdown. It seems to be in the range of noise. However, this idea serves as the beginning of some bigger optimizations coming in the following patches.

Acked-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
---
 merge-ort.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/merge-ort.c b/merge-ort.c
index e3a5dfc7b31..6299b4f9413 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -1023,6 +1023,43 @@ static int collect_merge_info_callback(int n,
 		return mask;
 	}
 
+	/*
+	 * If the sides match, and all three paths are present and are
+	 * files, then we can take either as the resolution.  We can't do
+	 * this with trees, because there may be rename sources from the
+	 * merge_base.
+	 */
+	if (sides_match && filemask == 0x07) {
+		/* use side1 (== side2) version as resolution */
+		setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
+				names, names+1, side1_null, 0,
+				filemask, dirmask, 1);
+		return mask;
+	}
+
+	/*
+	 * If side1 matches mbase and all three paths are present and are
+	 * files, then we can use side2 as the resolution.  We cannot
+	 * necessarily do so this for trees, because there may be rename
+	 * destinations within side2.
+	 */
+	if (side1_matches_mbase && filemask == 0x07) {
+		/* use side2 version as resolution */
+		setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
+				names, names+2, side2_null, 0,
+				filemask, dirmask, 1);
+		return mask;
+	}
+
+	/* Similar to above but swapping sides 1 and 2 */
+	if (side2_matches_mbase && filemask == 0x07) {
+		/* use side1 version as resolution */
+		setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
+				names, names+1, side1_null, 0,
+				filemask, dirmask, 1);
+		return mask;
+	}
+
 	/*
 	 * Gather additional information used in rename detection.
 	 */

-- 
gitgitgadget