| Message ID | 20201102204344.342633-8-newren@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fundamentals of merge-ort implementation | expand |
On 11/2/2020 3:43 PM, Elijah Newren wrote: > @@ -99,6 +99,15 @@ static int collect_merge_info_callback(int n, > unsigned mbase_null = !(mask & 1); > unsigned side1_null = !(mask & 2); > unsigned side2_null = !(mask & 4); > + unsigned side1_matches_mbase = (!side1_null && !mbase_null && > + names[0].mode == names[1].mode && > + oideq(&names[0].oid, &names[1].oid)); > + unsigned side2_matches_mbase = (!side2_null && !mbase_null && > + names[0].mode == names[2].mode && > + oideq(&names[0].oid, &names[2].oid)); > + unsigned sides_match = (!side1_null && !side2_null && > + names[1].mode == names[2].mode && > + oideq(&names[1].oid, &names[2].oid)); If the *_null values were in an array, instead, then all of these lines could be grouped as a macro: unsigned null_oid[3] = { !(mask & 1), !(mask & 2), !(mask & 4) }; #define trivial_merge(i,j) (!null_oid[i] && !null_oid[j] && \ names[i].mode == names[j].mode && \ oideq(&names[i].oid, &names[j].oid)) unsigned side1_matches_mbase = trivial_merge(0, 1); unsigned side2_matches_mbase = trivial_merge(0, 2); unsigned sides_match = trivial_merge(1, 2); I briefly considered making these last three an array, as well, except the loop below doesn't use 'i' in a symmetrical way: > + if (i == 1 && side1_matches_mbase) > + t[1] = t[0]; > + else if (i == 2 && side2_matches_mbase) > + t[2] = t[0]; > + else if (i == 2 && sides_match) > + t[2] = t[1]; Since the 'i == 2' case has two possible options, it wouldn't be possible to just have 'side_matches[i]' here. > + else { > + const struct object_id *oid = NULL; > + if (dirmask & 1) > + oid = &names[i].oid; > + buf[i] = fill_tree_descriptor(opt->repo, > + t + i, oid); > + } I do appreciate the reduced recursion here! Thanks, -Stolee
On Wed, Nov 11, 2020 at 6:51 AM Derrick Stolee <stolee@gmail.com> wrote: > > On 11/2/2020 3:43 PM, Elijah Newren wrote: > > @@ -99,6 +99,15 @@ static int collect_merge_info_callback(int n, > > unsigned mbase_null = !(mask & 1); > > unsigned side1_null = !(mask & 2); > > unsigned side2_null = !(mask & 4); > > + unsigned side1_matches_mbase = (!side1_null && !mbase_null && > > + names[0].mode == names[1].mode && > > + oideq(&names[0].oid, &names[1].oid)); > > + unsigned side2_matches_mbase = (!side2_null && !mbase_null && > > + names[0].mode == names[2].mode && > > + oideq(&names[0].oid, &names[2].oid)); > > + unsigned sides_match = (!side1_null && !side2_null && > > + names[1].mode == names[2].mode && > > + oideq(&names[1].oid, &names[2].oid)); > > If the *_null values were in an array, instead, then all of these > lines could be grouped as a macro: > > unsigned null_oid[3] = { > !(mask & 1), > !(mask & 2), > !(mask & 4) > }; > > #define trivial_merge(i,j) (!null_oid[i] && !null_oid[j] && \ > names[i].mode == names[j].mode && \ > oideq(&names[i].oid, &names[j].oid)) > > unsigned side1_matches_mbase = trivial_merge(0, 1); > unsigned side2_matches_mbase = trivial_merge(0, 2); > unsigned sides_match = trivial_merge(1, 2); Hmm, I like it. I think I'll rename trivial_merge() to non_null_match() (trivial merge suggests it can immediately be resolved which is not necessarily true if rename detection is on), but otherwise I'll use this. > I briefly considered making these last three an array, as well, > except the loop below doesn't use 'i' in a symmetrical way: > > > + if (i == 1 && side1_matches_mbase) > > + t[1] = t[0]; > > + else if (i == 2 && side2_matches_mbase) > > + t[2] = t[0]; > > + else if (i == 2 && sides_match) > > + t[2] = t[1]; > > Since the 'i == 2' case has two possible options, it wouldn't be > possible to just have 'side_matches[i]' here. > > > + else { > > + const struct object_id *oid = NULL; > > + if (dirmask & 1) > > + oid = &names[i].oid; > > + buf[i] = fill_tree_descriptor(opt->repo, > > + t + i, oid); > > + } > > I do appreciate the reduced recursion here! Technically, not my own optimization; I just copied from unpack-trees.c:traverse_trees_recursive() -- though the code looks slightly different because I didn't want to compare oids multiple times (I use the side match variables earlier in the function as well).
On Wed, Nov 11, 2020 at 12:13 PM Elijah Newren <newren@gmail.com> wrote: > On Wed, Nov 11, 2020 at 6:51 AM Derrick Stolee <stolee@gmail.com> wrote: > > If the *_null values were in an array, instead, then all of these > > lines could be grouped as a macro: > > > > unsigned null_oid[3] = { > > !(mask & 1), > > !(mask & 2), > > !(mask & 4) > > }; > > Hmm, I like it. I think I'll rename trivial_merge() to > non_null_match() (trivial merge suggests it can immediately be > resolved which is not necessarily true if rename detection is on), but > otherwise I'll use this. Are we allowing non-constant array initializers in the codebase these days? I don't see anything in CodingGuidelines suggesting the use of them.
diff --git a/merge-ort.c b/merge-ort.c index 626eb9713e..d3c1d00fc6 100644 --- a/merge-ort.c +++ b/merge-ort.c @@ -99,6 +99,15 @@ static int collect_merge_info_callback(int n, unsigned mbase_null = !(mask & 1); unsigned side1_null = !(mask & 2); unsigned side2_null = !(mask & 4); + unsigned side1_matches_mbase = (!side1_null && !mbase_null && + names[0].mode == names[1].mode && + oideq(&names[0].oid, &names[1].oid)); + unsigned side2_matches_mbase = (!side2_null && !mbase_null && + names[0].mode == names[2].mode && + oideq(&names[0].oid, &names[2].oid)); + unsigned sides_match = (!side1_null && !side2_null && + names[1].mode == names[2].mode && + oideq(&names[1].oid, &names[2].oid)); /* n = 3 is a fundamental assumption. */ if (n != 3) @@ -154,10 +163,19 @@ static int collect_merge_info_callback(int n, newinfo.pathlen = st_add3(newinfo.pathlen, p->pathlen, 1); for (i = 0; i < 3; i++, dirmask >>= 1) { - const struct object_id *oid = NULL; - if (dirmask & 1) - oid = &names[i].oid; - buf[i] = fill_tree_descriptor(opt->repo, t + i, oid); + if (i == 1 && side1_matches_mbase) + t[1] = t[0]; + else if (i == 2 && side2_matches_mbase) + t[2] = t[0]; + else if (i == 2 && sides_match) + t[2] = t[1]; + else { + const struct object_id *oid = NULL; + if (dirmask & 1) + oid = &names[i].oid; + buf[i] = fill_tree_descriptor(opt->repo, + t + i, oid); + } } original_dir_name = opti->current_dir_name;
Three-way merges, by their nature, are going to often have two or more trees match at a given subdirectory. We can avoid calling fill_tree_descriptor() on the same tree by checking when these trees match. Noting when various oids match will also be useful in other calculations and optimizations as well. Signed-off-by: Elijah Newren <newren@gmail.com> --- merge-ort.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-)