From c96fc0812393c3e2744232c1f6e248776628397f Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <ian@gcc.gnu.org>
Date: Tue, 10 Sep 2019 02:48:24 +0000
Subject: cmd/go: look for tool build ID before hashing entire file

    Also fix the key used to store the ID.

    This is a significant speedup in cmd/go run time.

    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/194257

From-SVN: r275559
---
 libgo/go/cmd/go/internal/work/buildid.go | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

(limited to 'libgo')

diff --git a/libgo/go/cmd/go/internal/work/buildid.go b/libgo/go/cmd/go/internal/work/buildid.go
index 1f6d1e8..5ff9337 100644
--- a/libgo/go/cmd/go/internal/work/buildid.go
+++ b/libgo/go/cmd/go/internal/work/buildid.go
@@ -291,14 +291,19 @@ func (b *Builder) gccgoToolID(name, language string) (string, error) {
 				exe = lp
 			}
 		}
-		if _, err := os.Stat(exe); err != nil {
-			return "", fmt.Errorf("%s: can not find compiler %q: %v; output %q", name, exe, err, out)
+		id, err = buildid.ReadFile(exe)
+		if err != nil {
+			return "", err
+		}
+
+		// If we can't find a build ID, use a hash.
+		if id == "" {
+			id = b.fileHash(exe)
 		}
-		id = b.fileHash(exe)
 	}
 
 	b.id.Lock()
-	b.toolIDCache[name] = id
+	b.toolIDCache[key] = id
 	b.id.Unlock()
 
 	return id, nil
-- 
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