cmd/compile: simplify fingerprint logic

Historically, we sometimes recorded imports based on either package
path ("net/http") or object file path ("net/http.a"). But modern Go
build systems always use package path, and the extra ".a" suffix
doesn't mean anything anyway.

Change-Id: I6060ef8bafa324168710d152a353f4d8db062133
Reviewed-on: https://go-review.googlesource.com/c/go/+/395254
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

2 files changed, 17 insertions, 46 deletions

diff --git a/src/cmd/compile/internal/noder/import.go b/src/cmd/compile/internal/noder/import.go
index 0898a298eb..7ba1b23d12 100644
--- a/src/cmd/compile/internal/noder/import.go
+++ b/src/cmd/compile/internal/noder/import.go
@@ -369,16 +369,8 @@ func addFingerprint(path string, f *os.File, end int64) error {
 	}
 
 	copy(fingerprint[:], buf[:])
+	base.Ctxt.AddImport(path, fingerprint)
 
-	// assume files move (get installed) so don't record the full path
-	if base.Flag.Cfg.PackageFile != nil {
-		// If using a packageFile map, assume path_ can be recorded directly.
-		base.Ctxt.AddImport(path, fingerprint)
-	} else {
-		// For file "/Users/foo/go/pkg/darwin_amd64/math.a" record "math.a".
-		file := f.Name()
-		base.Ctxt.AddImport(file[len(file)-len(path)-len(".a"):], fingerprint)
-	}
 	return nil
 }
 
diff --git a/src/cmd/link/internal/ld/ld.go b/src/cmd/link/internal/ld/ld.go
index 954921844c..aaad152e6f 100644
--- a/src/cmd/link/internal/ld/ld.go
+++ b/src/cmd/link/internal/ld/ld.go
@@ -96,19 +96,7 @@ func (ctxt *Link) readImportCfg(file string) {
 }
 
 func pkgname(ctxt *Link, lib string) string {
-	name := path.Clean(lib)
-
-	// When using importcfg, we have the final package name.
-	if ctxt.PackageFile != nil {
-		return name
-	}
-
-	// runtime.a -> runtime, runtime.6 -> runtime
-	pkg := name
-	if len(pkg) >= 2 && pkg[len(pkg)-2] == '.' {
-		pkg = pkg[:len(pkg)-2]
-	}
-	return pkg
+	return path.Clean(lib)
 }
 
 func findlib(ctxt *Link, lib string) (string, bool) {
@@ -127,34 +115,25 @@ func findlib(ctxt *Link, lib string) (string, bool) {
 			return "", false
 		}
 	} else {
-		if filepath.IsAbs(name) {
-			pname = name
-		} else {
-			pkg := pkgname(ctxt, lib)
-			// Add .a if needed; the new -importcfg modes
-			// do not put .a into the package name anymore.
-			// This only matters when people try to mix
-			// compiles using -importcfg with links not using -importcfg,
-			// such as when running quick things like
-			// 'go tool compile x.go && go tool link x.o'
-			// by hand against a standard library built using -importcfg.
-			if !strings.HasSuffix(name, ".a") && !strings.HasSuffix(name, ".o") {
-				name += ".a"
-			}
-			// try dot, -L "libdir", and then goroot.
-			for _, dir := range ctxt.Libdir {
-				if ctxt.linkShared {
-					pname = filepath.Join(dir, pkg+".shlibname")
-					if _, err := os.Stat(pname); err == nil {
-						isshlib = true
-						break
-					}
-				}
-				pname = filepath.Join(dir, name)
+		pkg := pkgname(ctxt, lib)
+
+		// search -L "libdir" directories
+		for _, dir := range ctxt.Libdir {
+			if ctxt.linkShared {
+				pname = filepath.Join(dir, pkg+".shlibname")
 				if _, err := os.Stat(pname); err == nil {
+					isshlib = true
 					break
 				}
 			}
+			pname = filepath.Join(dir, name+".a")
+			if _, err := os.Stat(pname); err == nil {
+				break
+			}
+			pname = filepath.Join(dir, name+".o")
+			if _, err := os.Stat(pname); err == nil {
+				break
+			}
 		}
 		pname = filepath.Clean(pname)
 	}