cmd/compile: remove FS debug hash form

The FS form was only necessary for reliable hashes in tests,
and for that we can use -trimpath.

Another potential concern would be temporary work directory
names leaking into the names of files generated by cgo and the
like, but we already make sure to avoid those to ensure
reproducible builds: the compiler never sees those paths.
So the FS form is not necessary for that either.

Change-Id: Idae2c6acb22ab64dfb33bb053244d23fbe153830
Reviewed-on: https://go-review.googlesource.com/c/go/+/493737
Run-TryBot: Russ Cox <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: David Chase <[email protected]>

src/cmd/compile/internal/base/flag.go

@@ -213,15 +213,7 @@ func ParseFlags() {
 
 	if Debug.LoopVarHash != "" {
 		// This first little bit controls the inputs for debug-hash-matching.
-		basenameOnly := false
 		mostInlineOnly := true
-		if strings.HasPrefix(Debug.LoopVarHash, "FS") {
-			// Magic handshake for testing, use file suffixes only when hashing on a position.
-			// i.e., rather than /tmp/asdfasdfasdf/go-test-whatever/foo_test.go,
-			// hash only on "foo_test.go", so that it will be the same hash across all runs.
-			Debug.LoopVarHash = Debug.LoopVarHash[2:]
-			basenameOnly = true
-		}
 		if strings.HasPrefix(Debug.LoopVarHash, "IL") {
 			// When hash-searching on a position that is an inline site, default is to use the
 			// most-inlined position only.  This makes the hash faster, plus there's no point
@@ -237,7 +229,6 @@ func ParseFlags() {
 			Debug.LoopVar = 1 // 1 means those loops that syntactically escape their dcl vars are eligible.
 		}
 		LoopVarHash.SetInlineSuffixOnly(mostInlineOnly)
-		LoopVarHash.SetFileSuffixOnly(basenameOnly)
 	} else if buildcfg.Experiment.LoopVar && Debug.LoopVar == 0 {
 		Debug.LoopVar = 1
 	}

src/cmd/compile/internal/base/hashdebug.go

@@ -40,14 +40,6 @@ type HashDebug struct {
 	inlineSuffixOnly bool // for Pos hashes, remove all but the most inline position.
 }
 
-// SetFileSuffixOnly controls whether hashing and reporting use the entire
-// file path name, just the basename.  This makes hashing more consistent,
-// at the expense of being able to certainly locate the file.
-func (d *HashDebug) SetFileSuffixOnly(b bool) *HashDebug {
-	d.fileSuffixOnly = b
-	return d
-}
-
 // SetInlineSuffixOnly controls whether hashing and reporting use the entire
 // inline position, or just the most-inline suffix.  Compiler debugging tends
 // to want the whole inlining, debugging user problems (loopvarhash, e.g.)

src/cmd/compile/internal/loopvar/loopvar_test.go

@@ -178,29 +178,40 @@ func TestLoopVarHashes(t *testing.T) {
 	root := "cmd/compile/internal/loopvar/testdata/inlines"
 
 	f := func(hash string) string {
-		// This disables the loopvar change, except for the specified package.
-		// The effect should follow the package, even though everything (except "c")
-		// is inlined.
-		cmd := testenv.Command(t, gocmd, "run", root)
-		cmd.Env = append(cmd.Env, "GOCOMPILEDEBUG=loopvarhash=FS"+hash, "HOME="+tmpdir)
+		// This disables the loopvar change, except for the specified hash pattern.
+		// -trimpath is necessary so we get the same answer no matter where the
+		// Go repository is checked out. This is not normally a concern since people
+		// do not rely on the meaning of specific hashes.
+		cmd := testenv.Command(t, gocmd, "run", "-trimpath", root)
+		cmd.Env = append(cmd.Env, "GOCOMPILEDEBUG=loopvarhash="+hash, "HOME="+tmpdir)
 		cmd.Dir = filepath.Join("testdata", "inlines")
 
 		b, _ := cmd.CombinedOutput()
 		// Ignore the error, sometimes it's supposed to fail, the output test will catch it.
 		return string(b)
 	}
 
-	m := f("011011011110011110111101")
+	m := f("001100110110110010100100")
 	t.Logf(m)
 
-	mCount := strings.Count(m, "loopvarhash triggered main.go:27:6")
+	mCount := strings.Count(m, "loopvarhash triggered cmd/compile/internal/loopvar/testdata/inlines/main.go:27:6 001100110110110010100100")
 	otherCount := strings.Count(m, "loopvarhash")
 	if mCount < 1 {
-		t.Errorf("Did not see expected value of m compile")
+		t.Errorf("did not see triggered main.go:27:6")
 	}
 	if mCount != otherCount {
-		t.Errorf("Saw extraneous hash matches")
+		t.Errorf("too many matches")
 	}
+
+	mCount = strings.Count(m, "cmd/compile/internal/loopvar/testdata/inlines/main.go:27:6 [bisect-match 0x7802e115b9336ca4]")
+	otherCount = strings.Count(m, "[bisect-match ")
+	if mCount < 1 {
+		t.Errorf("did not see bisect-match for main.go:27:6")
+	}
+	if mCount != otherCount {
+		t.Errorf("too many matches")
+	}
+
 	// This next test carefully dodges a bug-to-be-fixed with inlined locations for ir.Names.
 	if !strings.Contains(m, ", 100, 100, 100, 100") {
 		t.Errorf("Did not see expected value of m run")