From 59ed0136210a276ff9574a9b7008bcb7b7f9cb8b Mon Sep 17 00:00:00 2001
From: Keith Randall <khr@golang.org>
Date: Fri, 5 Dec 2025 14:45:38 -0800
Subject: [PATCH] cmd/compile: simplify array parsing in equality signatures

Change-Id: I166586a1f75165cd17df371f9af7cd5b6b3ddc32
Reviewed-on: https://go-review.googlesource.com/c/go/+/727502
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
---
 src/cmd/compile/internal/reflectdata/alg.go | 102 +++++++-------------
 1 file changed, 33 insertions(+), 69 deletions(-)

diff --git a/src/cmd/compile/internal/reflectdata/alg.go b/src/cmd/compile/internal/reflectdata/alg.go
index b281b4c37f0..c87cd8e257a 100644
--- a/src/cmd/compile/internal/reflectdata/alg.go
+++ b/src/cmd/compile/internal/reflectdata/alg.go
@@ -125,7 +125,6 @@ func hashFunc(sig string) *ir.Func {
 	if sym.Def != nil {
 		return sym.Def.(*ir.Name).Func
 	}
-	sig0 := sig
 
 	pos := base.AutogeneratedPos // less confusing than end of input
 	base.Pos = pos
@@ -211,29 +210,9 @@ func hashFunc(sig string) *ir.Func {
 			off += n
 		case sigArrayStart:
 			var n int64
-			n, sig = parseNum(sig)
-			// Find matching closing brace.
-			i := 0
-			depth := 1
-		findEndSquareBracket:
-			for {
-				if i == len(sig) {
-					base.Fatalf("mismatched brackets in %s", sig0)
-				}
-				switch sig[i] {
-				case sigArrayStart:
-					depth++
-				case sigArrayEnd:
-					depth--
-					if depth == 0 {
-						break findEndSquareBracket
-					}
-				}
-				i++
-			}
-			elemSig := sig[:i]
+			var elemSig string
+			n, elemSig, sig = parseArray(sig)
 			elemSize := sigSize(elemSig)
-			sig = sig[i+1:] // remaining signature after array
 
 			// Loop N times, calling hash function for the element.
 			//     for i := off; i < off + N*elemSize; i += elemSize {
@@ -381,7 +360,6 @@ func eqFunc(sig string) *ir.Func {
 	if sym.Def != nil {
 		return sym.Def.(*ir.Name).Func
 	}
-	sig0 := sig
 
 	pos := base.AutogeneratedPos // less confusing than end of input
 	base.Pos = pos
@@ -553,29 +531,9 @@ func eqFunc(sig string) *ir.Func {
 			}
 
 			var n int64
-			n, sig = parseNum(sig)
-			// Find matching closing brace.
-			i := 0
-			depth := 1
-		findEndSquareBracket:
-			for {
-				if i == len(sig) {
-					base.Fatalf("mismatched brackets in %s", sig0)
-				}
-				switch sig[i] {
-				case sigArrayStart:
-					depth++
-				case sigArrayEnd:
-					depth--
-					if depth == 0 {
-						break findEndSquareBracket
-					}
-				}
-				i++
-			}
-			elemSig := sig[:i]
+			var elemSig string
+			n, elemSig, sig = parseArray(sig)
 			elemSize := sigSize(elemSig)
-			sig = sig[i+1:] // remaining signature after array
 
 			// Loop N times, calling comparison function for the element.
 			//     for i := off; i < off + N*elemSize; i += elemSize {
@@ -898,9 +856,34 @@ func parseNum(s string) (int64, string) {
 	return x, s[n:]
 }
 
+// parseArray parses "%d%s]" from the front of a signature.
+// Returns the repeat count (the %d), the element signature
+// (the %s), and any remaining signature after the closing ']'.
+func parseArray(sig string) (int64, string, string) {
+	var n int64
+	n, sig = parseNum(sig)
+	// Find matching closing brace.
+	i := 0
+	depth := 1
+	for {
+		if i == len(sig) {
+			base.Fatalf("mismatched brackets in %s", sig)
+		}
+		switch sig[i] {
+		case sigArrayStart:
+			depth++
+		case sigArrayEnd:
+			depth--
+			if depth == 0 {
+				return n, sig[:i], sig[i+1:]
+			}
+		}
+		i++
+	}
+}
+
 // sigSize returns the size of the type described by the signature.
 func sigSize(sig string) int64 {
-	sig0 := sig
 	var size int64
 	for len(sig) > 0 {
 		kind := sig[0]
@@ -918,28 +901,9 @@ func sigSize(sig string) int64 {
 			size += 2 * int64(types.PtrSize)
 		case sigArrayStart:
 			var n int64
-			n, sig = parseNum(sig)
-			// Find matching closing brace.
-			i := 0
-			depth := 1
-		findEndSquareBracket:
-			for {
-				if i == len(sig) {
-					base.Fatalf("mismatched brackets in %s", sig0)
-				}
-				switch sig[i] {
-				case sigArrayStart:
-					depth++
-				case sigArrayEnd:
-					depth--
-					if depth == 0 {
-						break findEndSquareBracket
-					}
-				}
-				i++
-			}
-			size += n * sigSize(sig[:i])
-			sig = sig[i+1:]
+			var elemSig string
+			n, elemSig, sig = parseArray(sig)
+			size += n * sigSize(elemSig)
 		}
 	}
 	return size