[dev.regabi] strconv: add to bootstrap packages

go/constant relies on strconv for parsing Go literals, while older
versions of strconv either lack recent Go language features (e.g., Go
1.13's new numeric literals) or have errors (e.g., mishandling of
carriage returns in raw string literals prior to Go 1.8).

This requires two changes:

1. Splitting out the internal/bytealg dependency into a separate file,
which can be easily substituted with a simple loop for bootstrap
builds.

2. Updating eisel_lemire.go to not utilize Go 1.13 functionality
(underscores in numeric literals and signed shift counts).

Change-Id: Ib48a858a03b155eebdcd08d577aec2254337e70e
Reviewed-on: https://go-review.googlesource.com/c/go/+/272749
Reviewed-by: Robert Griesemer <gri@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/gc/dep_test.go

@@ -18,7 +18,7 @@ func TestDeps(t *testing.T) {
 	}
 	for _, dep := range strings.Fields(strings.Trim(string(out), "[]")) {
 		switch dep {
-		case "go/build", "go/token":
+		case "go/build", "go/scanner":
 			t.Errorf("undesired dependency on %q", dep)
 		}
 	}

src/cmd/dist/buildtool.go

@@ -96,6 +96,7 @@ var bootstrapDirs = []string{
 	"debug/elf",
 	"debug/macho",
 	"debug/pe",
+	"go/constant",
 	"internal/goversion",
 	"internal/race",
 	"internal/unsafeheader",
@@ -103,6 +104,7 @@ var bootstrapDirs = []string{
 	"math/big",
 	"math/bits",
 	"sort",
+	"strconv",
 }
 
 // File prefixes that are ignored by go/build anyway, and cause

src/strconv/bytealg.go

@@ -0,0 +1,14 @@
+// Copyright 2009 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.
+
+// +build !compiler_bootstrap
+
+package strconv
+
+import "internal/bytealg"
+
+// contains reports whether the string contains the byte c.
+func contains(s string, c byte) bool {
+	return bytealg.IndexByteString(s, c) != -1
+}

src/strconv/bytealg_bootstrap.go

@@ -0,0 +1,17 @@
+// 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.
+
+// +build compiler_bootstrap
+
+package strconv
+
+// contains reports whether the string contains the byte c.
+func contains(s string, c byte) bool {
+	for i := 0; i < len(s); i++ {
+		if s[i] == c {
+			return true
+		}
+	}
+	return false
+}

src/strconv/eisel_lemire.go

@@ -29,7 +29,7 @@ func eiselLemire64(man uint64, exp10 int, neg bool) (f float64, ok bool) {
 	// Exp10 Range.
 	if man == 0 {
 		if neg {
-			f = math.Float64frombits(0x80000000_00000000) // Negative zero.
+			f = math.Float64frombits(0x8000000000000000) // Negative zero.
 		}
 		return f, true
 	}
@@ -39,7 +39,7 @@ func eiselLemire64(man uint64, exp10 int, neg bool) (f float64, ok bool) {
 
 	// Normalization.
 	clz := bits.LeadingZeros64(man)
-	man <<= clz
+	man <<= uint(clz)
 	const float64ExponentBias = 1023
 	retExp2 := uint64(217706*exp10>>16+64+float64ExponentBias) - uint64(clz)
 
@@ -84,9 +84,9 @@ func eiselLemire64(man uint64, exp10 int, neg bool) (f float64, ok bool) {
 	if retExp2-1 >= 0x7FF-1 {
 		return 0, false
 	}
-	retBits := retExp2<<52 | retMantissa&0x000FFFFF_FFFFFFFF
+	retBits := retExp2<<52 | retMantissa&0x000FFFFFFFFFFFFF
 	if neg {
-		retBits |= 0x80000000_00000000
+		retBits |= 0x8000000000000000
 	}
 	return math.Float64frombits(retBits), true
 }
@@ -114,7 +114,7 @@ func eiselLemire32(man uint64, exp10 int, neg bool) (f float32, ok bool) {
 
 	// Normalization.
 	clz := bits.LeadingZeros64(man)
-	man <<= clz
+	man <<= uint(clz)
 	const float32ExponentBias = 127
 	retExp2 := uint64(217706*exp10>>16+64+float32ExponentBias) - uint64(clz)
 
@@ -122,13 +122,13 @@ func eiselLemire32(man uint64, exp10 int, neg bool) (f float32, ok bool) {
 	xHi, xLo := bits.Mul64(man, detailedPowersOfTen[exp10-detailedPowersOfTenMinExp10][1])
 
 	// Wider Approximation.
-	if xHi&0x3F_FFFFFFFF == 0x3F_FFFFFFFF && xLo+man < man {
+	if xHi&0x3FFFFFFFFF == 0x3FFFFFFFFF && xLo+man < man {
 		yHi, yLo := bits.Mul64(man, detailedPowersOfTen[exp10-detailedPowersOfTenMinExp10][0])
 		mergedHi, mergedLo := xHi, xLo+yHi
 		if mergedLo < xLo {
 			mergedHi++
 		}
-		if mergedHi&0x3F_FFFFFFFF == 0x3F_FFFFFFFF && mergedLo+1 == 0 && yLo+man < man {
+		if mergedHi&0x3FFFFFFFFF == 0x3FFFFFFFFF && mergedLo+1 == 0 && yLo+man < man {
 			return 0, false
 		}
 		xHi, xLo = mergedHi, mergedLo
@@ -140,7 +140,7 @@ func eiselLemire32(man uint64, exp10 int, neg bool) (f float32, ok bool) {
 	retExp2 -= 1 ^ msb
 
 	// Half-way Ambiguity.
-	if xLo == 0 && xHi&0x3F_FFFFFFFF == 0 && retMantissa&3 == 1 {
+	if xLo == 0 && xHi&0x3FFFFFFFFF == 0 && retMantissa&3 == 1 {
 		return 0, false
 	}
 

src/strconv/quote.go

@@ -7,7 +7,6 @@
 package strconv
 
 import (
-	"internal/bytealg"
 	"unicode/utf8"
 )
 
@@ -436,11 +435,6 @@ func Unquote(s string) (string, error) {
 	return string(buf), nil
 }
 
-// contains reports whether the string contains the byte c.
-func contains(s string, c byte) bool {
-	return bytealg.IndexByteString(s, c) != -1
-}
-
 // bsearch16 returns the smallest i such that a[i] >= x.
 // If there is no such i, bsearch16 returns len(a).
 func bsearch16(a []uint16, x uint16) int {