1 files changed, 24 insertions, 9 deletions

diff --git a/src/cmd/internal/testdir/testdir_test.go b/src/cmd/internal/testdir/testdir_test.go
index c706089877..e4d5b5d70b 100644
--- a/src/cmd/internal/testdir/testdir_test.go
+++ b/src/cmd/internal/testdir/testdir_test.go
@@ -1394,10 +1394,11 @@ type wantedError struct {
 }
 
 var (
-	errRx       = regexp.MustCompile(`// (?:GC_)?ERROR (.*)`)
-	errAutoRx   = regexp.MustCompile(`// (?:GC_)?ERRORAUTO (.*)`)
-	errQuotesRx = regexp.MustCompile(`"([^"]*)"`)
-	lineRx      = regexp.MustCompile(`LINE(([+-])(\d+))?`)
+	errRx            = regexp.MustCompile(`// (?:GC_)?ERROR (.*)`)
+	errAutoRx        = regexp.MustCompile(`// (?:GC_)?ERRORAUTO (.*)`)
+	errQuotesRx      = regexp.MustCompile(`"([^"]*)"`)
+	lineRx           = regexp.MustCompile(`LINE(([+-])(\d+))?`)
+	possibleOpcodeRx = regexp.MustCompile(`([A-Z][A-Z]|[IF](32|64))`) // two caps, or a wasm prefix
 )
 
 func (t test) wantedErrors(file, short string) (errs []wantedError) {
@@ -1477,7 +1478,7 @@ var (
 	// followed by semi-colon, followed by a comma-separated list of opcode checks.
 	// Extraneous spaces are ignored.
 	//
-	// An example: arm64/v8.1 : -`ADD` , `SUB`
+	// An example: arm64/v8.1 : -`ADD` `SUB`
 	//	"(\w+)" matches "arm64" (architecture name)
 	//	"(/[\w.]+)?" matches "v8.1" (architecture version)
 	//	"(/\w*)?" doesn't match anything here (it's an optional part of the triplet)
@@ -1485,10 +1486,11 @@ var (
 	//	"(" starts a capturing group
 	//      first reMatchCheck matches "-`ADD`"
 	//	`(?:" starts a non-capturing group
-	//	"\s*,\s*` matches " , "
+	//	"[\s,]+" matches " "
 	//	second reMatchCheck matches "`SUB`"
-	//	")*)" closes started groups; "*" means that there might be other elements in the comma-separated list
-	rxAsmPlatform = regexp.MustCompile(`(\w+)(/[\w.]+)?(/\w*)?\s*:\s*(` + reMatchCheck + `(?:\s+` + reMatchCheck + `)*)`)
+	//	")*)" closes started groups; "*" means that there might be other elements in the space-separated list
+	// (TODO: remove allowance for comma-separation once the repo is all fixed.)
+	rxAsmPlatform = regexp.MustCompile(`(\w+)(/[\w.]+)?(/\w*)?\s*:\s*(` + reMatchCheck + `(?:[\s,]+` + reMatchCheck + `)*)`)
 
 	// Regexp to extract a single opcoded check
 	rxAsmCheck = regexp.MustCompile(reMatchCheck)
@@ -1582,9 +1584,10 @@ func (t test) wantedAsmOpcodes(fn string) asmChecks {
 		// Parse and extract any architecture check from comments,
 		// made by one architecture name and multiple checks.
 		lnum := fn + ":" + strconv.Itoa(i+1)
+		lastUsed := 0
 		for _, ac := range rxAsmPlatform.FindAllStringSubmatch(comment, -1) {
 			archspec, allchecks := ac[1:4], ac[4]
-
+			lastUsed = strings.LastIndex(comment, allchecks) + len(allchecks)
 			var arch, subarch, os string
 			switch {
 			case archspec[2] != "": // 3 components: "linux/386/sse2"
@@ -1670,6 +1673,18 @@ func (t test) wantedAsmOpcodes(fn string) asmChecks {
 				}
 			}
 		}
+		if lastUsed > 0 {
+			// There was an asm spec in this comment. Check for possible syntax
+			// errors, which would leave some asm patterns unused. We want
+			//  to allow some tail, for example for English comments. The
+			// hueristic we use here is we look for two consecutive capital
+			// letters (or a wasm prefix). Those are probably assembly mnemonics
+			// that weren't used.
+			tail := comment[lastUsed:]
+			if possibleOpcodeRx.MatchString(tail) {
+				t.Errorf("%s:%d: possible unused assembly pattern: %v", t.goFileName(), i+1, tail)
+			}
+		}
 		comment = ""
 	}