cmd/internal/obj: add tool to generate Cnames string

Add cmd/internal/obj/mkcnames.go to do the generation and update
the architecture packages to use it to maintain the Cnames tables.

Currently works correctly on arm64,loong64,mips,ppc64 and s390x.

Change-Id: I5220b0ba6d8a8a5fcc4d9774731eb2af69a671af
Reviewed-on: https://go-review.googlesource.com/c/go/+/622256
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Meidan Li <limeidan@loongson.cn>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Qiqi Huang <huangqiqi@loongson.cn>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: sophie zhao <zhaoxiaolin@loongson.cn>
Commit-Queue: Ian Lance Taylor <iant@golang.org>

src/cmd/internal/obj/arm64/a.out.go

@@ -337,6 +337,7 @@ const (
 	NOSCHED
 )
 
+//go:generate go run ../mkcnames.go -i a.out.go -o anames7.go -p arm64
 const (
 	// optab is sorted based on the order of these constants
 	// and the first match is chosen.

src/cmd/internal/obj/arm64/anames7.go

@@ -1,10 +1,8 @@
-// Copyright 2015 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+// Code generated by mkcnames -i a.out.go -o anames7.go -p arm64; DO NOT EDIT.
 
 package arm64
 
-// This order should be strictly consistent to that in a.out.go
+// This order should be strictly consistent to that in a.out.go.
 var cnames7 = []string{
 	"", // C_NONE starts from 1
 	"NONE",
@@ -17,8 +15,8 @@ var cnames7 = []string{
 	"SHIFT",
 	"EXTREG",
 	"SPR",
-	"SPOP",
 	"COND",
+	"SPOP",
 	"ARNG",
 	"ELEM",
 	"LIST",
@@ -72,7 +70,7 @@ var cnames7 = []string{
 	"UAUTO16K_16",
 	"UAUTO16K_8",
 	"UAUTO16K",
-	"UAUTO32K_8",
+	"UAUTO32K_16",
 	"UAUTO32K",
 	"UAUTO64K",
 	"LAUTOPOOL",

src/cmd/internal/obj/loong64/a.out.go

@@ -316,6 +316,7 @@ const (
 	REG_LAST = REG_ELEM_END // the last defined register
 )
 
+//go:generate go run ../mkcnames.go -i a.out.go -o cnames.go -p loong64
 const (
 	C_NONE = iota
 	C_REG

src/cmd/internal/obj/loong64/cnames.go

@@ -1,6 +1,4 @@
-// Copyright 2022 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+// Code generated by mkcnames -i a.out.go -o cnames.go -p loong64; DO NOT EDIT.
 
 package loong64
 

src/cmd/internal/obj/mips/a.out.go

@@ -275,6 +275,7 @@ const (
 	NSCHED = 20
 )
 
+//go:generate go run ../mkcnames.go -i a.out.go -o anames0.go -p mips
 const (
 	C_NONE = iota
 	C_REG

src/cmd/internal/obj/mips/anames0.go

@@ -1,9 +1,8 @@
-// Copyright 2015 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+// Code generated by mkcnames -i a.out.go -o anames0.go -p mips; DO NOT EDIT.
 
 package mips
 
+// This order should be strictly consistent to that in a.out.go.
 var cnames0 = []string{
 	"NONE",
 	"REG",

src/cmd/internal/obj/mkcnames.go

@@ -0,0 +1,136 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build ignore
+
+// This is based on the implementation of src/cmd/internal/obj/stringer.go.
+// This is a mini version of the stringer tool customized for the Cnames
+// table in the architecture support for obj.
+
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"regexp"
+	"strings"
+)
+
+var (
+	input  = flag.String("i", "", "input file name")
+	output = flag.String("o", "", "output file name")
+	pkg    = flag.String("p", "", "package name")
+)
+
+var cnameExp = regexp.MustCompile(`^\tC_([A-Za-z0-9_]+)`)
+
+func main() {
+	flag.Parse()
+	if *input == "" || *output == "" || *pkg == "" {
+		flag.Usage()
+		os.Exit(2)
+	}
+
+	start := ""
+	switch *pkg {
+	case "arm64":
+		start = "var cnames7 = []string{\n\t\"\", // C_NONE starts from 1\n"
+	case "loong64", "mips":
+		start = "var cnames0 = []string{\n"
+	case "ppc64":
+		start = "var cnames9 = []string{\n"
+	case "s390x":
+		start = "var cnamesz = []string{\n"
+	default:
+		fmt.Printf("Only supports generating Cnames for arm64,loong64,mips,ppc64,s390x.")
+		os.Exit(0)
+	}
+
+	in, err := os.Open(*input)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fd, err := os.Create(*output)
+	if err != nil {
+		log.Fatal(err)
+	}
+	out := bufio.NewWriter(fd)
+	closeOut := func() {
+		if err = out.Flush(); err != nil {
+			log.Fatal(err)
+		}
+
+		if err = fd.Close(); err != nil {
+			log.Fatal(err)
+		}
+	}
+	defer closeOut()
+
+	on := false
+	s := bufio.NewScanner(in)
+	for s.Scan() {
+		line := s.Text()
+		if !on {
+			// First relevant line contains "C_NONE = iota".
+			// If we find it, delete the "=" so we don't stop immediately.
+			const first = "C_NONE"
+			if !strings.Contains(line, first) {
+				continue
+			}
+
+			const suffix = "= iota"
+			index := strings.Index(line, suffix)
+			if index < 0 {
+				continue
+			}
+			line = line[:index]
+
+			// It's on. Start with the header.
+			fmt.Fprintf(out, header, *input, *output, *pkg, *pkg)
+			fmt.Fprintf(out, start)
+			on = true
+		}
+
+		// Strip comments so their text won't defeat our heuristic.
+		index := strings.Index(line, "//")
+		if index > 0 {
+			line = line[:index]
+		}
+		index = strings.Index(line, "/*")
+		if index > 0 {
+			comments := line[index:]
+			if !strings.Contains(comments, "*/") {
+				log.Fatalf("invalid comment: %s\n", comments)
+			}
+			line = line[:index]
+		}
+
+		// Termination condition: Any line with an = changes the sequence,
+		// so stop there, and stop at a closing brace.
+		if strings.HasPrefix(line, "}") || strings.ContainsRune(line, '=') {
+			break
+		}
+
+		sub := cnameExp.FindStringSubmatch(line)
+		if len(sub) < 2 {
+			continue
+		} else {
+			fmt.Fprintf(out, "\t%q,\n", sub[1])
+		}
+	}
+	fmt.Fprintln(out, "}")
+	if s.Err() != nil {
+		log.Fatal(err)
+	}
+}
+
+const header = `// Code generated by mkcnames -i %s -o %s -p %s; DO NOT EDIT.
+
+package %s
+
+// This order should be strictly consistent to that in a.out.go.
+`

src/cmd/internal/obj/ppc64/a.out.go

@@ -399,6 +399,7 @@ const (
 	C_COND_SO        // 3 summary overflow or FP compare w/ NaN
 )
 
+//go:generate go run ../mkcnames.go -i a.out.go -o anames9.go -p ppc64
 const (
 	C_NONE     = iota
 	C_REGP     /* An even numbered gpr which can be used a gpr pair argument */

src/cmd/internal/obj/ppc64/anames9.go

@@ -1,9 +1,8 @@
-// Copyright 2015 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+// Code generated by mkcnames -i a.out.go -o anames9.go -p ppc64; DO NOT EDIT.
 
 package ppc64
 
+// This order should be strictly consistent to that in a.out.go.
 var cnames9 = []string{
 	"NONE",
 	"REGP",
@@ -16,7 +15,7 @@ var cnames9 = []string{
 	"CREG",
 	"CRBIT",
 	"SPR",
-	"MREG",
+	"AREG",
 	"ZCON",
 	"U1CON",
 	"U2CON",

src/cmd/internal/obj/s390x/a.out.go

@@ -189,6 +189,7 @@ const (
 	USETMP // generated code of this Prog uses REGTMP
 )
 
+//go:generate go run ../mkcnames.go -i a.out.go -o anamesz.go -p s390x
 const ( // comments from func aclass in asmz.go
 	C_NONE     = iota
 	C_REG      // general-purpose register (64-bit)

src/cmd/internal/obj/s390x/anamesz.go

@@ -1,9 +1,8 @@
-// Copyright 2016 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+// Code generated by mkcnames -i a.out.go -o anamesz.go -p s390x; DO NOT EDIT.
 
 package s390x
 
+// This order should be strictly consistent to that in a.out.go.
 var cnamesz = []string{
 	"NONE",
 	"REG",