cmd/internal/ssa: correct references to _gen folder

The gen folder was renamed to _gen in CL 435472, but references in code
and docs were not updated. This updates the references.

Change-Id: Ibadc0cdcb5bed145c3257b58465a8df370487ae5
Reviewed-on: https://go-review.googlesource.com/c/go/+/444355
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/compile/internal/ssa/README.md

@@ -34,7 +34,7 @@ value is defined exactly once, but it may be used any number of times. A value
 mainly consists of a unique identifier, an operator, a type, and some arguments.
 
 An operator or `Op` describes the operation that computes the value. The
-semantics of each operator can be found in `gen/*Ops.go`. For example, `OpAdd8`
+semantics of each operator can be found in `_gen/*Ops.go`. For example, `OpAdd8`
 takes two value arguments holding 8-bit integers and results in their addition.
 Here is a possible SSA representation of the addition of two `uint8` values:
 
@@ -205,16 +205,16 @@ TODO: need more ideas for this section
 
 While most compiler passes are implemented directly in Go code, some others are
 code generated. This is currently done via rewrite rules, which have their own
-syntax and are maintained in `gen/*.rules`. Simpler optimizations can be written
+syntax and are maintained in `_gen/*.rules`. Simpler optimizations can be written
 easily and quickly this way, but rewrite rules are not suitable for more complex
 optimizations.
 
 To read more on rewrite rules, have a look at the top comments in
-[gen/generic.rules](gen/generic.rules) and [gen/rulegen.go](gen/rulegen.go).
+[_gen/generic.rules](_gen/generic.rules) and [_gen/rulegen.go](_gen/rulegen.go).
 
 Similarly, the code to manage operators is also code generated from
-`gen/*Ops.go`, as it is easier to maintain a few tables than a lot of code.
-After changing the rules or operators, see [gen/README](gen/README) for
+`_gen/*Ops.go`, as it is easier to maintain a few tables than a lot of code.
+After changing the rules or operators, see [_gen/README](_gen/README) for
 instructions on how to generate the Go code again.
 
 <!---

src/cmd/compile/internal/ssa/_gen/cover.bash

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash 
+#!/usr/bin/env bash
 # Copyright 2020 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.
@@ -9,7 +9,7 @@
 #     ./cover.bash && go tool cover -html=cover.out
 #
 # This script is needed to set up a temporary test file, so that we don't break
-# regular 'go run *.go' usage to run the generator.
+# regular 'go run .' usage to run the generator.
 
 cat >main_test.go <<-EOF
 	// +build ignore

src/cmd/compile/internal/ssa/_gen/main.go

@@ -188,7 +188,7 @@ func main() {
 
 func genOp() {
 	w := new(bytes.Buffer)
-	fmt.Fprintf(w, "// Code generated from gen/*Ops.go; DO NOT EDIT.\n")
+	fmt.Fprintf(w, "// Code generated from _gen/*Ops.go; DO NOT EDIT.\n")
 	fmt.Fprintln(w)
 	fmt.Fprintln(w, "package ssa")
 

src/cmd/compile/internal/ssa/_gen/rulegen.go

@@ -576,8 +576,8 @@ func fprint(w io.Writer, n Node) {
 	case *File:
 		file := n
 		seenRewrite := make(map[[3]string]string)
-		fmt.Fprintf(w, "// Code generated from gen/%s%s.rules; DO NOT EDIT.\n", n.Arch.name, n.Suffix)
-		fmt.Fprintf(w, "// generated with: cd gen; go run *.go\n")
+		fmt.Fprintf(w, "// Code generated from _gen/%s%s.rules; DO NOT EDIT.\n", n.Arch.name, n.Suffix)
+		fmt.Fprintf(w, "// generated with: cd _gen; go run .\n")
 		fmt.Fprintf(w, "\npackage ssa\n")
 		for _, path := range append([]string{
 			"fmt",

src/cmd/compile/internal/ssa/addressingmodes.go

@@ -196,7 +196,7 @@ var combine = map[[2]Op]Op{
 	[2]Op{OpAMD64MOVQstoreconst, OpAMD64LEAQ8}: OpAMD64MOVQstoreconstidx8,
 
 	// These instructions are re-split differently for performance, see needSplit above.
-	// TODO if 386 versions are created, also update needSplit and gen/386splitload.rules
+	// TODO if 386 versions are created, also update needSplit and _gen/386splitload.rules
 	[2]Op{OpAMD64CMPBload, OpAMD64ADDQ}: OpAMD64CMPBloadidx1,
 	[2]Op{OpAMD64CMPWload, OpAMD64ADDQ}: OpAMD64CMPWloadidx1,
 	[2]Op{OpAMD64CMPLload, OpAMD64ADDQ}: OpAMD64CMPLloadidx1,

src/cmd/compile/internal/ssa/op.go

@@ -16,7 +16,7 @@ import (
 // An Op encodes the specific operation that a Value performs.
 // Opcodes' semantics can be modified by the type and aux fields of the Value.
 // For instance, OpAdd can be 32 or 64 bit, signed or unsigned, float or complex, depending on Value.Type.
-// Semantics of each op are described in the opcode files in gen/*Ops.go.
+// Semantics of each op are described in the opcode files in _gen/*Ops.go.
 // There is one file for generic (architecture-independent) ops and one file
 // for each architecture.
 type Op int32

src/cmd/compile/internal/ssa/opGen.go

@@ -1,4 +1,4 @@
-// Code generated from gen/*Ops.go; DO NOT EDIT.
+// Code generated from _gen/*Ops.go; DO NOT EDIT.
 
 package ssa
 

src/cmd/compile/internal/ssa/regalloc.go

@@ -626,7 +626,7 @@ func (s *regAllocState) init(f *Func) {
 			// Note that for Flag_shared (position independent code)
 			// we do need to be careful, but that carefulness is hidden
 			// in the rewrite rules so we always have a free register
-			// available for global load/stores. See gen/386.rules (search for Flag_shared).
+			// available for global load/stores. See _gen/386.rules (search for Flag_shared).
 		case "amd64":
 			s.allocatable &^= 1 << 15 // R15
 		case "arm":

src/cmd/compile/internal/ssa/rewrite.go

@@ -1165,7 +1165,7 @@ func ccARM64Eval(op Op, flags *Value) int {
 }
 
 // logRule logs the use of the rule s. This will only be enabled if
-// rewrite rules were generated with the -log option, see gen/rulegen.go.
+// rewrite rules were generated with the -log option, see _gen/rulegen.go.
 func logRule(s string) {
 	if ruleFile == nil {
 		// Open a log file to write log to. We open in append

src/cmd/compile/internal/ssa/rewrite386.go

@@ -1,5 +1,5 @@
-// Code generated from gen/386.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/386.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewrite386splitload.go

@@ -1,5 +1,5 @@
-// Code generated from gen/386splitload.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/386splitload.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteAMD64.go

@@ -1,5 +1,5 @@
-// Code generated from gen/AMD64.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/AMD64.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteAMD64latelower.go

@@ -1,5 +1,5 @@
-// Code generated from gen/AMD64latelower.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/AMD64latelower.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteAMD64splitload.go

@@ -1,5 +1,5 @@
-// Code generated from gen/AMD64splitload.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/AMD64splitload.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteARM.go

@@ -1,5 +1,5 @@
-// Code generated from gen/ARM.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/ARM.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteARM64.go

@@ -1,5 +1,5 @@
-// Code generated from gen/ARM64.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/ARM64.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteARM64latelower.go

@@ -1,5 +1,5 @@
-// Code generated from gen/ARM64latelower.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/ARM64latelower.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteLOONG64.go

@@ -1,5 +1,5 @@
-// Code generated from gen/LOONG64.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/LOONG64.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteMIPS.go

@@ -1,5 +1,5 @@
-// Code generated from gen/MIPS.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/MIPS.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteMIPS64.go

@@ -1,5 +1,5 @@
-// Code generated from gen/MIPS64.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/MIPS64.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewritePPC64.go

@@ -1,5 +1,5 @@
-// Code generated from gen/PPC64.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/PPC64.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteRISCV64.go

@@ -1,5 +1,5 @@
-// Code generated from gen/RISCV64.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/RISCV64.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteRISCV64latelower.go

@@ -1,5 +1,5 @@
-// Code generated from gen/RISCV64latelower.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/RISCV64latelower.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteS390X.go

@@ -1,5 +1,5 @@
-// Code generated from gen/S390X.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/S390X.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewriteWasm.go

@@ -1,5 +1,5 @@
-// Code generated from gen/Wasm.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/Wasm.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewritedec.go

@@ -1,5 +1,5 @@
-// Code generated from gen/dec.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/dec.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewritedec64.go

@@ -1,5 +1,5 @@
-// Code generated from gen/dec64.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/dec64.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa
 

src/cmd/compile/internal/ssa/rewritegeneric.go

@@ -1,5 +1,5 @@
-// Code generated from gen/generic.rules; DO NOT EDIT.
-// generated with: cd gen; go run *.go
+// Code generated from _gen/generic.rules; DO NOT EDIT.
+// generated with: cd _gen; go run .
 
 package ssa