From: penglei <penglei@ybyte.org>
Date: Mon, 9 May 2022 08:55:41 +0000 (+0000)
Subject: cmd/go/internal/mvs: Delete redundant searching  for maximum version when building... 
X-Git-Tag: go1.19beta1~255
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=e755a5649aac75f43283a5ec160445b4478c8182;p=gostls13.git

cmd/go/internal/mvs: Delete redundant searching  for maximum version when building minimal requirement list

mvs.Req performs an unnecessary search for the maximum version when building minimal requirement list. Someone may be confused when reading this piece of code. The comment of the BuildList function also states that the build list contains the maximum version of each module. We just need to create a maximum version cache that maps from path to version, in the beginning of the Req function body.

Change-Id: I4b353e167f2dcc96bc13cc2e1c602bce47c72bc9
GitHub-Last-Rev: fce11d3c728450f71cb0b6e5478792f0133b8cfc
GitHub-Pull-Request: golang/go#50345
Reviewed-on: https://go-review.googlesource.com/c/go/+/374277
Auto-Submit: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
---

diff --git a/src/cmd/go/internal/mvs/mvs.go b/src/cmd/go/internal/mvs/mvs.go
index d25d447b0e..a1b51557a3 100644
--- a/src/cmd/go/internal/mvs/mvs.go
+++ b/src/cmd/go/internal/mvs/mvs.go
@@ -194,6 +194,11 @@ func Req(mainModule module.Version, base []string, reqs Reqs) ([]module.Version,
 	// that list came from a previous operation that paged
 	// in all the requirements, so there's no I/O to overlap now.
 
+	max := map[string]string{}
+	for _, m := range list {
+		max[m.Path] = m.Version
+	}
+
 	// Compute postorder, cache requirements.
 	var postorder []module.Version
 	reqCache := map[module.Version][]module.Version{}
@@ -236,14 +241,6 @@ func Req(mainModule module.Version, base []string, reqs Reqs) ([]module.Version,
 		}
 		return nil
 	}
-	max := map[string]string{}
-	for _, m := range list {
-		if v, ok := max[m.Path]; ok {
-			max[m.Path] = reqs.Max(m.Version, v)
-		} else {
-			max[m.Path] = m.Version
-		}
-	}
 	// First walk the base modules that must be listed.
 	var min []module.Version
 	haveBase := map[string]bool{}