libgo: update to Go 1.13beta1 release

    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/193497

From-SVN: r275473

11 files changed, 874 insertions, 150 deletions

diff --git a/libgo/go/strconv/atof.go b/libgo/go/strconv/atof.go
index fdcb8b3..eff1379 100644
--- a/libgo/go/strconv/atof.go
+++ b/libgo/go/strconv/atof.go
@@ -13,7 +13,7 @@ package strconv
 import "math"
 import "runtime"
 
-var optimize = true // can change for testing
+var optimize = true // set to false to force slow-path conversions for testing
 
 func equalIgnoreCase(s1, s2 string) bool {
 	if len(s1) != len(s2) {
@@ -84,6 +84,9 @@ func (b *decimal) set(s string) (ok bool) {
 	sawdigits := false
 	for ; i < len(s); i++ {
 		switch {
+		case s[i] == '_':
+			// underscoreOK already called
+			continue
 		case s[i] == '.':
 			if sawdot {
 				return
@@ -120,7 +123,7 @@ func (b *decimal) set(s string) (ok bool) {
 	// just be sure to move the decimal point by
 	// a lot (say, 100000).  it doesn't matter if it's
 	// not the exact number.
-	if i < len(s) && (s[i] == 'e' || s[i] == 'E') {
+	if i < len(s) && lower(s[i]) == 'e' {
 		i++
 		if i >= len(s) {
 			return
@@ -136,7 +139,11 @@ func (b *decimal) set(s string) (ok bool) {
 			return
 		}
 		e := 0
-		for ; i < len(s) && '0' <= s[i] && s[i] <= '9'; i++ {
+		for ; i < len(s) && ('0' <= s[i] && s[i] <= '9' || s[i] == '_'); i++ {
+			if s[i] == '_' {
+				// underscoreOK already called
+				continue
+			}
 			if e < 10000 {
 				e = e*10 + int(s[i]) - '0'
 			}
@@ -153,10 +160,9 @@ func (b *decimal) set(s string) (ok bool) {
 }
 
 // readFloat reads a decimal mantissa and exponent from a float
-// string representation. It sets ok to false if the number could
+// string representation. It returns ok==false if the number could
 // not fit return types or is invalid.
-func readFloat(s string) (mantissa uint64, exp int, neg, trunc, ok bool) {
-	const uint64digits = 19
+func readFloat(s string) (mantissa uint64, exp int, neg, trunc, hex, ok bool) {
 	i := 0
 
 	// optional sign
@@ -172,6 +178,16 @@ func readFloat(s string) (mantissa uint64, exp int, neg, trunc, ok bool) {
 	}
 
 	// digits
+	base := uint64(10)
+	maxMantDigits := 19 // 10^19 fits in uint64
+	expChar := byte('e')
+	if i+2 < len(s) && s[i] == '0' && lower(s[i+1]) == 'x' {
+		base = 16
+		maxMantDigits = 16 // 16^16 fits in uint64
+		i += 2
+		expChar = 'p'
+		hex = true
+	}
 	sawdot := false
 	sawdigits := false
 	nd := 0
@@ -179,6 +195,10 @@ func readFloat(s string) (mantissa uint64, exp int, neg, trunc, ok bool) {
 	dp := 0
 	for ; i < len(s); i++ {
 		switch c := s[i]; true {
+		case c == '_':
+			// underscoreOK already called
+			continue
+
 		case c == '.':
 			if sawdot {
 				return
@@ -194,11 +214,23 @@ func readFloat(s string) (mantissa uint64, exp int, neg, trunc, ok bool) {
 				continue
 			}
 			nd++
-			if ndMant < uint64digits {
-				mantissa *= 10
+			if ndMant < maxMantDigits {
+				mantissa *= base
 				mantissa += uint64(c - '0')
 				ndMant++
-			} else if s[i] != '0' {
+			} else if c != '0' {
+				trunc = true
+			}
+			continue
+
+		case base == 16 && 'a' <= lower(c) && lower(c) <= 'f':
+			sawdigits = true
+			nd++
+			if ndMant < maxMantDigits {
+				mantissa *= 16
+				mantissa += uint64(lower(c) - 'a' + 10)
+				ndMant++
+			} else {
 				trunc = true
 			}
 			continue
@@ -212,12 +244,17 @@ func readFloat(s string) (mantissa uint64, exp int, neg, trunc, ok bool) {
 		dp = nd
 	}
 
+	if base == 16 {
+		dp *= 4
+		ndMant *= 4
+	}
+
 	// optional exponent moves decimal point.
 	// if we read a very large, very long number,
 	// just be sure to move the decimal point by
 	// a lot (say, 100000).  it doesn't matter if it's
 	// not the exact number.
-	if i < len(s) && (s[i] == 'e' || s[i] == 'E') {
+	if i < len(s) && lower(s[i]) == expChar {
 		i++
 		if i >= len(s) {
 			return
@@ -233,12 +270,19 @@ func readFloat(s string) (mantissa uint64, exp int, neg, trunc, ok bool) {
 			return
 		}
 		e := 0
-		for ; i < len(s) && '0' <= s[i] && s[i] <= '9'; i++ {
+		for ; i < len(s) && ('0' <= s[i] && s[i] <= '9' || s[i] == '_'); i++ {
+			if s[i] == '_' {
+				// underscoreOK already called
+				continue
+			}
 			if e < 10000 {
 				e = e*10 + int(s[i]) - '0'
 			}
 		}
 		dp += e * esign
+	} else if base == 16 {
+		// Must have exponent.
+		return
 	}
 
 	if i != len(s) {
@@ -250,7 +294,6 @@ func readFloat(s string) (mantissa uint64, exp int, neg, trunc, ok bool) {
 	}
 	ok = true
 	return
-
 }
 
 // decimal power of ten to binary power of two.
@@ -439,6 +482,76 @@ func atof32exact(mantissa uint64, exp int, neg bool) (f float32, ok bool) {
 	return
 }
 
+// atofHex converts the hex floating-point string s
+// to a rounded float32 or float64 value (depending on flt==&float32info or flt==&float64info)
+// and returns it as a float64.
+// The string s has already been parsed into a mantissa, exponent, and sign (neg==true for negative).
+// If trunc is true, trailing non-zero bits have been omitted from the mantissa.
+func atofHex(s string, flt *floatInfo, mantissa uint64, exp int, neg, trunc bool) (float64, error) {
+	maxExp := 1<<flt.expbits + flt.bias - 2
+	minExp := flt.bias + 1
+	exp += int(flt.mantbits) // mantissa now implicitly divided by 2^mantbits.
+
+	// Shift mantissa and exponent to bring representation into float range.
+	// Eventually we want a mantissa with a leading 1-bit followed by mantbits other bits.
+	// For rounding, we need two more, where the bottom bit represents
+	// whether that bit or any later bit was non-zero.
+	// (If the mantissa has already lost non-zero bits, trunc is true,
+	// and we OR in a 1 below after shifting left appropriately.)
+	for mantissa != 0 && mantissa>>(flt.mantbits+2) == 0 {
+		mantissa <<= 1
+		exp--
+	}
+	if trunc {
+		mantissa |= 1
+	}
+	for mantissa>>(1+flt.mantbits+2) != 0 {
+		mantissa = mantissa>>1 | mantissa&1
+		exp++
+	}
+
+	// If exponent is too negative,
+	// denormalize in hopes of making it representable.
+	// (The -2 is for the rounding bits.)
+	for mantissa > 1 && exp < minExp-2 {
+		mantissa = mantissa>>1 | mantissa&1
+		exp++
+	}
+
+	// Round using two bottom bits.
+	round := mantissa & 3
+	mantissa >>= 2
+	round |= mantissa & 1 // round to even (round up if mantissa is odd)
+	exp += 2
+	if round == 3 {
+		mantissa++
+		if mantissa == 1<<(1+flt.mantbits) {
+			mantissa >>= 1
+			exp++
+		}
+	}
+
+	if mantissa>>flt.mantbits == 0 { // Denormal or zero.
+		exp = flt.bias
+	}
+	var err error
+	if exp > maxExp { // infinity and range error
+		mantissa = 1 << flt.mantbits
+		exp = maxExp + 1
+		err = rangeError(fnParseFloat, s)
+	}
+
+	bits := mantissa & (1<<flt.mantbits - 1)
+	bits |= uint64((exp-flt.bias)&(1<<flt.expbits-1)) << flt.mantbits
+	if neg {
+		bits |= 1 << flt.mantbits << flt.expbits
+	}
+	if flt == &float32info {
+		return float64(math.Float32frombits(uint32(bits))), err
+	}
+	return math.Float64frombits(bits), err
+}
+
 const fnParseFloat = "ParseFloat"
 
 func atof32(s string) (f float32, err error) {
@@ -446,28 +559,32 @@ func atof32(s string) (f float32, err error) {
 		return float32(val), nil
 	}
 
-	if optimize {
-		// Parse mantissa and exponent.
-		mantissa, exp, neg, trunc, ok := readFloat(s)
-		if ok {
-			// Try pure floating-point arithmetic conversion.
-			if !trunc {
-				if f, ok := atof32exact(mantissa, exp, neg); ok {
-					return f, nil
-				}
+	mantissa, exp, neg, trunc, hex, ok := readFloat(s)
+	if hex && ok {
+		f, err := atofHex(s, &float32info, mantissa, exp, neg, trunc)
+		return float32(f), err
+	}
+
+	if optimize && ok {
+		// Try pure floating-point arithmetic conversion.
+		if !trunc {
+			if f, ok := atof32exact(mantissa, exp, neg); ok {
+				return f, nil
 			}
-			// Try another fast path.
-			ext := new(extFloat)
-			if ok := ext.AssignDecimal(mantissa, exp, neg, trunc, &float32info); ok {
-				b, ovf := ext.floatBits(&float32info)
-				f = math.Float32frombits(uint32(b))
-				if ovf {
-					err = rangeError(fnParseFloat, s)
-				}
-				return f, err
+		}
+		// Try another fast path.
+		ext := new(extFloat)
+		if ok := ext.AssignDecimal(mantissa, exp, neg, trunc, &float32info); ok {
+			b, ovf := ext.floatBits(&float32info)
+			f = math.Float32frombits(uint32(b))
+			if ovf {
+				err = rangeError(fnParseFloat, s)
 			}
+			return f, err
 		}
 	}
+
+	// Slow fallback.
 	var d decimal
 	if !d.set(s) {
 		return 0, syntaxError(fnParseFloat, s)
@@ -485,28 +602,31 @@ func atof64(s string) (f float64, err error) {
 		return val, nil
 	}
 
-	if optimize {
-		// Parse mantissa and exponent.
-		mantissa, exp, neg, trunc, ok := readFloat(s)
-		if ok {
-			// Try pure floating-point arithmetic conversion.
-			if !trunc {
-				if f, ok := atof64exact(mantissa, exp, neg); ok {
-					return f, nil
-				}
+	mantissa, exp, neg, trunc, hex, ok := readFloat(s)
+	if hex && ok {
+		return atofHex(s, &float64info, mantissa, exp, neg, trunc)
+	}
+
+	if optimize && ok {
+		// Try pure floating-point arithmetic conversion.
+		if !trunc {
+			if f, ok := atof64exact(mantissa, exp, neg); ok {
+				return f, nil
 			}
-			// Try another fast path.
-			ext := new(extFloat)
-			if ok := ext.AssignDecimal(mantissa, exp, neg, trunc, &float64info); ok {
-				b, ovf := ext.floatBits(&float64info)
-				f = math.Float64frombits(b)
-				if ovf {
-					err = rangeError(fnParseFloat, s)
-				}
-				return f, err
+		}
+		// Try another fast path.
+		ext := new(extFloat)
+		if ok := ext.AssignDecimal(mantissa, exp, neg, trunc, &float64info); ok {
+			b, ovf := ext.floatBits(&float64info)
+			f = math.Float64frombits(b)
+			if ovf {
+				err = rangeError(fnParseFloat, s)
 			}
+			return f, err
 		}
 	}
+
+	// Slow fallback.
 	var d decimal
 	if !d.set(s) {
 		return 0, syntaxError(fnParseFloat, s)
@@ -524,9 +644,13 @@ func atof64(s string) (f float64, err error) {
 // When bitSize=32, the result still has type float64, but it will be
 // convertible to float32 without changing its value.
 //
-// If s is well-formed and near a valid floating point number,
-// ParseFloat returns the nearest floating point number rounded
+// ParseFloat accepts decimal and hexadecimal floating-point number syntax.
+// If s is well-formed and near a valid floating-point number,
+// ParseFloat returns the nearest floating-point number rounded
 // using IEEE754 unbiased rounding.
+// (Parsing a hexadecimal floating-point value only rounds when
+// there are more bits in the hexadecimal representatiton than
+// will fit in the mantissa.)
 //
 // The errors that ParseFloat returns have concrete type *NumError
 // and include err.Num = s.
@@ -536,7 +660,13 @@ func atof64(s string) (f float64, err error) {
 // If s is syntactically well-formed but is more than 1/2 ULP
 // away from the largest floating point number of the given size,
 // ParseFloat returns f = ±Inf, err.Err = ErrRange.
+//
+// ParseFloat recognizes the strings "NaN", "+Inf", and "-Inf" as their
+// respective special floating point values. It ignores case when matching.
 func ParseFloat(s string, bitSize int) (float64, error) {
+	if !underscoreOK(s) {
+		return 0, syntaxError(fnParseFloat, s)
+	}
 	if bitSize == 32 {
 		f, err := atof32(s)
 		return float64(f), err
diff --git a/libgo/go/strconv/atof_test.go b/libgo/go/strconv/atof_test.go
index cf4d47c..abe6c64 100644
--- a/libgo/go/strconv/atof_test.go
+++ b/libgo/go/strconv/atof_test.go
@@ -43,6 +43,23 @@ var atoftests = []atofTest{
 	{"1e-20", "1e-20", nil},
 	{"625e-3", "0.625", nil},
 
+	// Hexadecimal floating-point.
+	{"0x1p0", "1", nil},
+	{"0x1p1", "2", nil},
+	{"0x1p-1", "0.5", nil},
+	{"0x1ep-1", "15", nil},
+	{"-0x1ep-1", "-15", nil},
+	{"-0x1_ep-1", "-15", nil},
+	{"0x1p-200", "6.223015277861142e-61", nil},
+	{"0x1p200", "1.6069380442589903e+60", nil},
+	{"0x1fFe2.p0", "131042", nil},
+	{"0x1fFe2.P0", "131042", nil},
+	{"-0x2p3", "-16", nil},
+	{"0x0.fp4", "15", nil},
+	{"0x0.fp0", "0.9375", nil},
+	{"0x1e2", "0", ErrSyntax},
+	{"1p2", "0", ErrSyntax},
+
 	// zeros
 	{"0", "0", nil},
 	{"0e0", "0", nil},
@@ -58,6 +75,11 @@ var atoftests = []atofTest{
 	{"0.00e-01234567890123456789", "0", nil},
 	{"-0e+01234567890123456789", "-0", nil},
 	{"-0.00e-01234567890123456789", "-0", nil},
+	{"0x0p+01234567890123456789", "0", nil},
+	{"0x0.00p-01234567890123456789", "0", nil},
+	{"-0x0p+01234567890123456789", "-0", nil},
+	{"-0x0.00p-01234567890123456789", "-0", nil},
+
 	{"0e291", "0", nil}, // issue 15364
 	{"0e292", "0", nil}, // issue 15364
 	{"0e347", "0", nil}, // issue 15364
@@ -66,6 +88,26 @@ var atoftests = []atofTest{
 	{"-0e292", "-0", nil},
 	{"-0e347", "-0", nil},
 	{"-0e348", "-0", nil},
+	{"0x0p126", "0", nil},
+	{"0x0p127", "0", nil},
+	{"0x0p128", "0", nil},
+	{"0x0p129", "0", nil},
+	{"0x0p130", "0", nil},
+	{"0x0p1022", "0", nil},
+	{"0x0p1023", "0", nil},
+	{"0x0p1024", "0", nil},
+	{"0x0p1025", "0", nil},
+	{"0x0p1026", "0", nil},
+	{"-0x0p126", "-0", nil},
+	{"-0x0p127", "-0", nil},
+	{"-0x0p128", "-0", nil},
+	{"-0x0p129", "-0", nil},
+	{"-0x0p130", "-0", nil},
+	{"-0x0p1022", "-0", nil},
+	{"-0x0p1023", "-0", nil},
+	{"-0x0p1024", "-0", nil},
+	{"-0x0p1025", "-0", nil},
+	{"-0x0p1026", "-0", nil},
 
 	// NaNs
 	{"nan", "NaN", nil},
@@ -83,21 +125,46 @@ var atoftests = []atofTest{
 	// largest float64
 	{"1.7976931348623157e308", "1.7976931348623157e+308", nil},
 	{"-1.7976931348623157e308", "-1.7976931348623157e+308", nil},
+	{"0x1.fffffffffffffp1023", "1.7976931348623157e+308", nil},
+	{"-0x1.fffffffffffffp1023", "-1.7976931348623157e+308", nil},
+	{"0x1fffffffffffffp+971", "1.7976931348623157e+308", nil},
+	{"-0x1fffffffffffffp+971", "-1.7976931348623157e+308", nil},
+	{"0x.1fffffffffffffp1027", "1.7976931348623157e+308", nil},
+	{"-0x.1fffffffffffffp1027", "-1.7976931348623157e+308", nil},
+
 	// next float64 - too large
 	{"1.7976931348623159e308", "+Inf", ErrRange},
 	{"-1.7976931348623159e308", "-Inf", ErrRange},
+	{"0x1p1024", "+Inf", ErrRange},
+	{"-0x1p1024", "-Inf", ErrRange},
+	{"0x2p1023", "+Inf", ErrRange},
+	{"-0x2p1023", "-Inf", ErrRange},
+	{"0x.1p1028", "+Inf", ErrRange},
+	{"-0x.1p1028", "-Inf", ErrRange},
+	{"0x.2p1027", "+Inf", ErrRange},
+	{"-0x.2p1027", "-Inf", ErrRange},
+
 	// the border is ...158079
 	// borderline - okay
 	{"1.7976931348623158e308", "1.7976931348623157e+308", nil},
 	{"-1.7976931348623158e308", "-1.7976931348623157e+308", nil},
+	{"0x1.fffffffffffff7fffp1023", "1.7976931348623157e+308", nil},
+	{"-0x1.fffffffffffff7fffp1023", "-1.7976931348623157e+308", nil},
 	// borderline - too large
 	{"1.797693134862315808e308", "+Inf", ErrRange},
 	{"-1.797693134862315808e308", "-Inf", ErrRange},
+	{"0x1.fffffffffffff8p1023", "+Inf", ErrRange},
+	{"-0x1.fffffffffffff8p1023", "-Inf", ErrRange},
+	{"0x1fffffffffffff.8p+971", "+Inf", ErrRange},
+	{"-0x1fffffffffffff8p+967", "-Inf", ErrRange},
+	{"0x.1fffffffffffff8p1027", "+Inf", ErrRange},
+	{"-0x.1fffffffffffff9p1027", "-Inf", ErrRange},
 
 	// a little too large
 	{"1e308", "1e+308", nil},
 	{"2e308", "+Inf", ErrRange},
 	{"1e309", "+Inf", ErrRange},
+	{"0x1p1025", "+Inf", ErrRange},
 
 	// way too large
 	{"1e310", "+Inf", ErrRange},
@@ -106,6 +173,12 @@ var atoftests = []atofTest{
 	{"-1e400", "-Inf", ErrRange},
 	{"1e400000", "+Inf", ErrRange},
 	{"-1e400000", "-Inf", ErrRange},
+	{"0x1p1030", "+Inf", ErrRange},
+	{"0x1p2000", "+Inf", ErrRange},
+	{"0x1p2000000000", "+Inf", ErrRange},
+	{"-0x1p1030", "-Inf", ErrRange},
+	{"-0x1p2000", "-Inf", ErrRange},
+	{"-0x1p2000000000", "-Inf", ErrRange},
 
 	// denormalized
 	{"1e-305", "1e-305", nil},
@@ -125,17 +198,75 @@ var atoftests = []atofTest{
 	{"1e-350", "0", nil},
 	{"1e-400000", "0", nil},
 
+	// Near denormals and denormals.
+	{"0x2.00000000000000p-1010", "1.8227805048890994e-304", nil}, // 0x00e0000000000000
+	{"0x1.fffffffffffff0p-1010", "1.8227805048890992e-304", nil}, // 0x00dfffffffffffff
+	{"0x1.fffffffffffff7p-1010", "1.8227805048890992e-304", nil}, // rounded down
+	{"0x1.fffffffffffff8p-1010", "1.8227805048890994e-304", nil}, // rounded up
+	{"0x1.fffffffffffff9p-1010", "1.8227805048890994e-304", nil}, // rounded up
+
+	{"0x2.00000000000000p-1022", "4.450147717014403e-308", nil},  // 0x0020000000000000
+	{"0x1.fffffffffffff0p-1022", "4.4501477170144023e-308", nil}, // 0x001fffffffffffff
+	{"0x1.fffffffffffff7p-1022", "4.4501477170144023e-308", nil}, // rounded down
+	{"0x1.fffffffffffff8p-1022", "4.450147717014403e-308", nil},  // rounded up
+	{"0x1.fffffffffffff9p-1022", "4.450147717014403e-308", nil},  // rounded up
+
+	{"0x1.00000000000000p-1022", "2.2250738585072014e-308", nil}, // 0x0010000000000000
+	{"0x0.fffffffffffff0p-1022", "2.225073858507201e-308", nil},  // 0x000fffffffffffff
+	{"0x0.ffffffffffffe0p-1022", "2.2250738585072004e-308", nil}, // 0x000ffffffffffffe
+	{"0x0.ffffffffffffe7p-1022", "2.2250738585072004e-308", nil}, // rounded down
+	{"0x1.ffffffffffffe8p-1023", "2.225073858507201e-308", nil},  // rounded up
+	{"0x1.ffffffffffffe9p-1023", "2.225073858507201e-308", nil},  // rounded up
+
+	{"0x0.00000003fffff0p-1022", "2.072261e-317", nil},  // 0x00000000003fffff
+	{"0x0.00000003456780p-1022", "1.694649e-317", nil},  // 0x0000000000345678
+	{"0x0.00000003456787p-1022", "1.694649e-317", nil},  // rounded down
+	{"0x0.00000003456788p-1022", "1.694649e-317", nil},  // rounded down (half to even)
+	{"0x0.00000003456790p-1022", "1.6946496e-317", nil}, // 0x0000000000345679
+	{"0x0.00000003456789p-1022", "1.6946496e-317", nil}, // rounded up
+
+	{"0x0.0000000345678800000000000000000000000001p-1022", "1.6946496e-317", nil}, // rounded up
+
+	{"0x0.000000000000f0p-1022", "7.4e-323", nil}, // 0x000000000000000f
+	{"0x0.00000000000060p-1022", "3e-323", nil},   // 0x0000000000000006
+	{"0x0.00000000000058p-1022", "3e-323", nil},   // rounded up
+	{"0x0.00000000000057p-1022", "2.5e-323", nil}, // rounded down
+	{"0x0.00000000000050p-1022", "2.5e-323", nil}, // 0x0000000000000005
+
+	{"0x0.00000000000010p-1022", "5e-324", nil},  // 0x0000000000000001
+	{"0x0.000000000000081p-1022", "5e-324", nil}, // rounded up
+	{"0x0.00000000000008p-1022", "0", nil},       // rounded down
+	{"0x0.00000000000007fp-1022", "0", nil},      // rounded down
+
 	// try to overflow exponent
 	{"1e-4294967296", "0", nil},
 	{"1e+4294967296", "+Inf", ErrRange},
 	{"1e-18446744073709551616", "0", nil},
 	{"1e+18446744073709551616", "+Inf", ErrRange},
+	{"0x1p-4294967296", "0", nil},
+	{"0x1p+4294967296", "+Inf", ErrRange},
+	{"0x1p-18446744073709551616", "0", nil},
+	{"0x1p+18446744073709551616", "+Inf", ErrRange},
 
 	// Parse errors
 	{"1e", "0", ErrSyntax},
 	{"1e-", "0", ErrSyntax},
 	{".e-1", "0", ErrSyntax},
 	{"1\x00.2", "0", ErrSyntax},
+	{"0x", "0", ErrSyntax},
+	{"0x.", "0", ErrSyntax},
+	{"0x1", "0", ErrSyntax},
+	{"0x.1", "0", ErrSyntax},
+	{"0x1p", "0", ErrSyntax},
+	{"0x.1p", "0", ErrSyntax},
+	{"0x1p+", "0", ErrSyntax},
+	{"0x.1p+", "0", ErrSyntax},
+	{"0x1p-", "0", ErrSyntax},
+	{"0x.1p-", "0", ErrSyntax},
+	{"0x1p+2", "4", nil},
+	{"0x.1p+2", "0.25", nil},
+	{"0x1p-2", "0.25", nil},
+	{"0x.1p-2", "0.015625", nil},
 
 	// https://www.exploringbinary.com/java-hangs-when-converting-2-2250738585072012e-308/
 	{"2.2250738585072012e-308", "2.2250738585072014e-308", nil},
@@ -148,42 +279,109 @@ var atoftests = []atofTest{
 	// A different kind of very large number.
 	{"22.222222222222222", "22.22222222222222", nil},
 	{"2." + strings.Repeat("2", 4000) + "e+1", "22.22222222222222", nil},
+	{"0x1.1111111111111p222", "7.18931911124017e+66", nil},
+	{"0x2.2222222222222p221", "7.18931911124017e+66", nil},
+	{"0x2." + strings.Repeat("2", 4000) + "p221", "7.18931911124017e+66", nil},
 
 	// Exactly halfway between 1 and math.Nextafter(1, 2).
 	// Round to even (down).
 	{"1.00000000000000011102230246251565404236316680908203125", "1", nil},
+	{"0x1.00000000000008p0", "1", nil},
 	// Slightly lower; still round down.
 	{"1.00000000000000011102230246251565404236316680908203124", "1", nil},
+	{"0x1.00000000000007Fp0", "1", nil},
 	// Slightly higher; round up.
 	{"1.00000000000000011102230246251565404236316680908203126", "1.0000000000000002", nil},
+	{"0x1.000000000000081p0", "1.0000000000000002", nil},
+	{"0x1.00000000000009p0", "1.0000000000000002", nil},
 	// Slightly higher, but you have to read all the way to the end.
 	{"1.00000000000000011102230246251565404236316680908203125" + strings.Repeat("0", 10000) + "1", "1.0000000000000002", nil},
+	{"0x1.00000000000008" + strings.Repeat("0", 10000) + "1p0", "1.0000000000000002", nil},
+
+	// Halfway between x := math.Nextafter(1, 2) and math.Nextafter(x, 2)
+	// Round to even (up).
+	{"1.00000000000000033306690738754696212708950042724609375", "1.0000000000000004", nil},
+	{"0x1.00000000000018p0", "1.0000000000000004", nil},
+
+	// Underscores.
+	{"1_23.50_0_0e+1_2", "1.235e+14", nil},
+	{"-_123.5e+12", "0", ErrSyntax},
+	{"+_123.5e+12", "0", ErrSyntax},
+	{"_123.5e+12", "0", ErrSyntax},
+	{"1__23.5e+12", "0", ErrSyntax},
+	{"123_.5e+12", "0", ErrSyntax},
+	{"123._5e+12", "0", ErrSyntax},
+	{"123.5_e+12", "0", ErrSyntax},
+	{"123.5__0e+12", "0", ErrSyntax},
+	{"123.5e_+12", "0", ErrSyntax},
+	{"123.5e+_12", "0", ErrSyntax},
+	{"123.5e_-12", "0", ErrSyntax},
+	{"123.5e-_12", "0", ErrSyntax},
+	{"123.5e+1__2", "0", ErrSyntax},
+	{"123.5e+12_", "0", ErrSyntax},
+
+	{"0x_1_2.3_4_5p+1_2", "74565", nil},
+	{"-_0x12.345p+12", "0", ErrSyntax},
+	{"+_0x12.345p+12", "0", ErrSyntax},
+	{"_0x12.345p+12", "0", ErrSyntax},
+	{"0x__12.345p+12", "0", ErrSyntax},
+	{"0x1__2.345p+12", "0", ErrSyntax},
+	{"0x12_.345p+12", "0", ErrSyntax},
+	{"0x12._345p+12", "0", ErrSyntax},
+	{"0x12.3__45p+12", "0", ErrSyntax},
+	{"0x12.345_p+12", "0", ErrSyntax},
+	{"0x12.345p_+12", "0", ErrSyntax},
+	{"0x12.345p+_12", "0", ErrSyntax},
+	{"0x12.345p_-12", "0", ErrSyntax},
+	{"0x12.345p-_12", "0", ErrSyntax},
+	{"0x12.345p+1__2", "0", ErrSyntax},
+	{"0x12.345p+12_", "0", ErrSyntax},
 }
 
 var atof32tests = []atofTest{
+	// Hex
+	{"0x1p-100", "7.888609e-31", nil},
+	{"0x1p100", "1.2676506e+30", nil},
+
 	// Exactly halfway between 1 and the next float32.
 	// Round to even (down).
 	{"1.000000059604644775390625", "1", nil},
+	{"0x1.000001p0", "1", nil},
 	// Slightly lower.
 	{"1.000000059604644775390624", "1", nil},
+	{"0x1.0000008p0", "1", nil},
+	{"0x1.000000fp0", "1", nil},
 	// Slightly higher.
 	{"1.000000059604644775390626", "1.0000001", nil},
+	{"0x1.000002p0", "1.0000001", nil},
+	{"0x1.0000018p0", "1.0000001", nil},
+	{"0x1.0000011p0", "1.0000001", nil},
 	// Slightly higher, but you have to read all the way to the end.
 	{"1.000000059604644775390625" + strings.Repeat("0", 10000) + "1", "1.0000001", nil},
+	{"0x1.000001" + strings.Repeat("0", 10000) + "1p0", "1.0000001", nil},
 
 	// largest float32: (1<<128) * (1 - 2^-24)
 	{"340282346638528859811704183484516925440", "3.4028235e+38", nil},
 	{"-340282346638528859811704183484516925440", "-3.4028235e+38", nil},
+	{"0x.ffffffp128", "3.4028235e+38", nil},
+	{"-340282346638528859811704183484516925440", "-3.4028235e+38", nil},
+	{"-0x.ffffffp128", "-3.4028235e+38", nil},
 	// next float32 - too large
 	{"3.4028236e38", "+Inf", ErrRange},
 	{"-3.4028236e38", "-Inf", ErrRange},
+	{"0x1.0p128", "+Inf", ErrRange},
+	{"-0x1.0p128", "-Inf", ErrRange},
 	// the border is 3.40282356779...e+38
 	// borderline - okay
 	{"3.402823567e38", "3.4028235e+38", nil},
 	{"-3.402823567e38", "-3.4028235e+38", nil},
+	{"0x.ffffff7fp128", "3.4028235e+38", nil},
+	{"-0x.ffffff7fp128", "-3.4028235e+38", nil},
 	// borderline - too large
 	{"3.4028235678e38", "+Inf", ErrRange},
 	{"-3.4028235678e38", "-Inf", ErrRange},
+	{"0x.ffffff8p128", "+Inf", ErrRange},
+	{"-0x.ffffff8p128", "-Inf", ErrRange},
 
 	// Denormals: less than 2^-126
 	{"1e-38", "1e-38", nil},
@@ -195,9 +393,24 @@ var atof32tests = []atofTest{
 	{"1e-44", "1e-44", nil},
 	{"6e-45", "6e-45", nil}, // 4p-149 = 5.6e-45
 	{"5e-45", "6e-45", nil},
+
 	// Smallest denormal
 	{"1e-45", "1e-45", nil}, // 1p-149 = 1.4e-45
 	{"2e-45", "1e-45", nil},
+	{"3e-45", "3e-45", nil},
+
+	// Near denormals and denormals.
+	{"0x0.89aBcDp-125", "1.2643093e-38", nil},  // 0x0089abcd
+	{"0x0.8000000p-125", "1.1754944e-38", nil}, // 0x00800000
+	{"0x0.1234560p-125", "1.671814e-39", nil},  // 0x00123456
+	{"0x0.1234567p-125", "1.671814e-39", nil},  // rounded down
+	{"0x0.1234568p-125", "1.671814e-39", nil},  // rounded down
+	{"0x0.1234569p-125", "1.671815e-39", nil},  // rounded up
+	{"0x0.1234570p-125", "1.671815e-39", nil},  // 0x00123457
+	{"0x0.0000010p-125", "1e-45", nil},         // 0x00000001
+	{"0x0.00000081p-125", "1e-45", nil},        // rounded up
+	{"0x0.0000008p-125", "0", nil},             // rounded down
+	{"0x0.0000007p-125", "0", nil},             // rounded down
 
 	// 2^92 = 8388608p+69 = 4951760157141521099596496896 (4.9517602e27)
 	// is an exact power of two that needs 8 decimal digits to be correctly
diff --git a/libgo/go/strconv/atoi.go b/libgo/go/strconv/atoi.go
index ff33d55..31774d0 100644
--- a/libgo/go/strconv/atoi.go
+++ b/libgo/go/strconv/atoi.go
@@ -6,6 +6,14 @@ package strconv
 
 import "errors"
 
+// lower(c) is a lower-case letter if and only if
+// c is either that lower-case letter or the equivalent upper-case letter.
+// Instead of writing c == 'x' || c == 'X' one can write lower(c) == 'x'.
+// Note that lower of non-letters can produce other non-letters.
+func lower(c byte) byte {
+	return c | ('x' - 'X')
+}
+
 // ErrRange indicates that a value is out of range for the target type.
 var ErrRange = errors.New("value out of range")
 
@@ -50,10 +58,12 @@ const maxUint64 = 1<<64 - 1
 func ParseUint(s string, base int, bitSize int) (uint64, error) {
 	const fnParseUint = "ParseUint"
 
-	if len(s) == 0 {
+	if s == "" || !underscoreOK(s) {
 		return 0, syntaxError(fnParseUint, s)
 	}
 
+	base0 := base == 0
+
 	s0 := s
 	switch {
 	case 2 <= base && base <= 36:
@@ -61,18 +71,22 @@ func ParseUint(s string, base int, bitSize int) (uint64, error) {
 
 	case base == 0:
 		// Look for octal, hex prefix.
-		switch {
-		case s[0] == '0' && len(s) > 1 && (s[1] == 'x' || s[1] == 'X'):
-			if len(s) < 3 {
-				return 0, syntaxError(fnParseUint, s0)
+		base = 10
+		if s[0] == '0' {
+			switch {
+			case len(s) >= 3 && lower(s[1]) == 'b':
+				base = 2
+				s = s[2:]
+			case len(s) >= 3 && lower(s[1]) == 'o':
+				base = 8
+				s = s[2:]
+			case len(s) >= 3 && lower(s[1]) == 'x':
+				base = 16
+				s = s[2:]
+			default:
+				base = 8
+				s = s[1:]
 			}
-			base = 16
-			s = s[2:]
-		case s[0] == '0':
-			base = 8
-			s = s[1:]
-		default:
-			base = 10
 		}
 
 	default:
@@ -103,12 +117,13 @@ func ParseUint(s string, base int, bitSize int) (uint64, error) {
 	for _, c := range []byte(s) {
 		var d byte
 		switch {
+		case c == '_' && base0:
+			// underscoreOK already called
+			continue
 		case '0' <= c && c <= '9':
 			d = c - '0'
-		case 'a' <= c && c <= 'z':
-			d = c - 'a' + 10
-		case 'A' <= c && c <= 'Z':
-			d = c - 'A' + 10
+		case 'a' <= lower(c) && lower(c) <= 'z':
+			d = lower(c) - 'a' + 10
 		default:
 			return 0, syntaxError(fnParseUint, s0)
 		}
@@ -138,13 +153,14 @@ func ParseUint(s string, base int, bitSize int) (uint64, error) {
 // bit size (0 to 64) and returns the corresponding value i.
 //
 // If base == 0, the base is implied by the string's prefix:
-// base 16 for "0x", base 8 for "0", and base 10 otherwise.
-// For bases 1, below 0 or above 36 an error is returned.
+// base 2 for "0b", base 8 for "0" or "0o", base 16 for "0x",
+// and base 10 otherwise.
+// If base is below 0, is 1, or is above 36, an error is returned.
 //
 // The bitSize argument specifies the integer type
 // that the result must fit into. Bit sizes 0, 8, 16, 32, and 64
 // correspond to int, int8, int16, int32, and int64.
-// For a bitSize below 0 or above 64 an error is returned.
+// If bitSize is below 0 or above 64, an error is returned.
 //
 // The errors that ParseInt returns have concrete type *NumError
 // and include err.Num = s. If s is empty or contains invalid
@@ -156,8 +172,7 @@ func ParseUint(s string, base int, bitSize int) (uint64, error) {
 func ParseInt(s string, base int, bitSize int) (i int64, err error) {
 	const fnParseInt = "ParseInt"
 
-	// Empty string bad.
-	if len(s) == 0 {
+	if s == "" {
 		return 0, syntaxError(fnParseInt, s)
 	}
 
@@ -228,10 +243,60 @@ func Atoi(s string) (int, error) {
 		return n, nil
 	}
 
-	// Slow path for invalid or big integers.
+	// Slow path for invalid, big, or underscored integers.
 	i64, err := ParseInt(s, 10, 0)
 	if nerr, ok := err.(*NumError); ok {
 		nerr.Func = fnAtoi
 	}
 	return int(i64), err
 }
+
+// underscoreOK reports whether the underscores in s are allowed.
+// Checking them in this one function lets all the parsers skip over them simply.
+// Underscore must appear only between digits or between a base prefix and a digit.
+func underscoreOK(s string) bool {
+	// saw tracks the last character (class) we saw:
+	// ^ for beginning of number,
+	// 0 for a digit or base prefix,
+	// _ for an underscore,
+	// ! for none of the above.
+	saw := '^'
+	i := 0
+
+	// Optional sign.
+	if len(s) >= 1 && (s[0] == '-' || s[0] == '+') {
+		s = s[1:]
+	}
+
+	// Optional base prefix.
+	hex := false
+	if len(s) >= 2 && s[0] == '0' && (lower(s[1]) == 'b' || lower(s[1]) == 'o' || lower(s[1]) == 'x') {
+		i = 2
+		saw = '0' // base prefix counts as a digit for "underscore as digit separator"
+		hex = lower(s[1]) == 'x'
+	}
+
+	// Number proper.
+	for ; i < len(s); i++ {
+		// Digits are always okay.
+		if '0' <= s[i] && s[i] <= '9' || hex && 'a' <= lower(s[i]) && lower(s[i]) <= 'f' {
+			saw = '0'
+			continue
+		}
+		// Underscore must follow digit.
+		if s[i] == '_' {
+			if saw != '0' {
+				return false
+			}
+			saw = '_'
+			continue
+		}
+		// Underscore must also be followed by digit.
+		if saw == '_' {
+			return false
+		}
+		// Saw non-digit, non-underscore.
+		saw = '!'
+	}
+	return saw != '_'
+}
diff --git a/libgo/go/strconv/atoi_test.go b/libgo/go/strconv/atoi_test.go
index e2f505a..b167c96 100644
--- a/libgo/go/strconv/atoi_test.go
+++ b/libgo/go/strconv/atoi_test.go
@@ -29,6 +29,10 @@ var parseUint64Tests = []parseUint64Test{
 	{"18446744073709551615", 1<<64 - 1, nil},
 	{"18446744073709551616", 1<<64 - 1, ErrRange},
 	{"18446744073709551620", 1<<64 - 1, ErrRange},
+	{"1_2_3_4_5", 0, ErrSyntax}, // base=10 so no underscores allowed
+	{"_12345", 0, ErrSyntax},
+	{"1__2345", 0, ErrSyntax},
+	{"12345_", 0, ErrSyntax},
 }
 
 type parseUint64BaseTest struct {
@@ -61,6 +65,69 @@ var parseUint64BaseTests = []parseUint64BaseTest{
 	{"01777777777777777777778", 0, 0, ErrSyntax},
 	{"02000000000000000000000", 0, 1<<64 - 1, ErrRange},
 	{"0200000000000000000000", 0, 1 << 61, nil},
+	{"0b", 0, 0, ErrSyntax},
+	{"0B", 0, 0, ErrSyntax},
+	{"0b101", 0, 5, nil},
+	{"0B101", 0, 5, nil},
+	{"0o", 0, 0, ErrSyntax},
+	{"0O", 0, 0, ErrSyntax},
+	{"0o377", 0, 255, nil},
+	{"0O377", 0, 255, nil},
+
+	// underscores allowed with base == 0 only
+	{"1_2_3_4_5", 0, 12345, nil}, // base 0 => 10
+	{"_12345", 0, 0, ErrSyntax},
+	{"1__2345", 0, 0, ErrSyntax},
+	{"12345_", 0, 0, ErrSyntax},
+
+	{"1_2_3_4_5", 10, 0, ErrSyntax}, // base 10
+	{"_12345", 10, 0, ErrSyntax},
+	{"1__2345", 10, 0, ErrSyntax},
+	{"12345_", 10, 0, ErrSyntax},
+
+	{"0x_1_2_3_4_5", 0, 0x12345, nil}, // base 0 => 16
+	{"_0x12345", 0, 0, ErrSyntax},
+	{"0x__12345", 0, 0, ErrSyntax},
+	{"0x1__2345", 0, 0, ErrSyntax},
+	{"0x1234__5", 0, 0, ErrSyntax},
+	{"0x12345_", 0, 0, ErrSyntax},
+
+	{"1_2_3_4_5", 16, 0, ErrSyntax}, // base 16
+	{"_12345", 16, 0, ErrSyntax},
+	{"1__2345", 16, 0, ErrSyntax},
+	{"1234__5", 16, 0, ErrSyntax},
+	{"12345_", 16, 0, ErrSyntax},
+
+	{"0_1_2_3_4_5", 0, 012345, nil}, // base 0 => 8 (0377)
+	{"_012345", 0, 0, ErrSyntax},
+	{"0__12345", 0, 0, ErrSyntax},
+	{"01234__5", 0, 0, ErrSyntax},
+	{"012345_", 0, 0, ErrSyntax},
+
+	{"0o_1_2_3_4_5", 0, 012345, nil}, // base 0 => 8 (0o377)
+	{"_0o12345", 0, 0, ErrSyntax},
+	{"0o__12345", 0, 0, ErrSyntax},
+	{"0o1234__5", 0, 0, ErrSyntax},
+	{"0o12345_", 0, 0, ErrSyntax},
+
+	{"0_1_2_3_4_5", 8, 0, ErrSyntax}, // base 8
+	{"_012345", 8, 0, ErrSyntax},
+	{"0__12345", 8, 0, ErrSyntax},
+	{"01234__5", 8, 0, ErrSyntax},
+	{"012345_", 8, 0, ErrSyntax},
+
+	{"0b_1_0_1", 0, 5, nil}, // base 0 => 2 (0b101)
+	{"_0b101", 0, 0, ErrSyntax},
+	{"0b__101", 0, 0, ErrSyntax},
+	{"0b1__01", 0, 0, ErrSyntax},
+	{"0b10__1", 0, 0, ErrSyntax},
+	{"0b101_", 0, 0, ErrSyntax},
+
+	{"1_0_1", 2, 0, ErrSyntax}, // base 2
+	{"_101", 2, 0, ErrSyntax},
+	{"1_01", 2, 0, ErrSyntax},
+	{"10_1", 2, 0, ErrSyntax},
+	{"101_", 2, 0, ErrSyntax},
 }
 
 type parseInt64Test struct {
@@ -87,6 +154,11 @@ var parseInt64Tests = []parseInt64Test{
 	{"-9223372036854775808", -1 << 63, nil},
 	{"9223372036854775809", 1<<63 - 1, ErrRange},
 	{"-9223372036854775809", -1 << 63, ErrRange},
+	{"-1_2_3_4_5", 0, ErrSyntax}, // base=10 so no underscores allowed
+	{"-_12345", 0, ErrSyntax},
+	{"_12345", 0, ErrSyntax},
+	{"1__2345", 0, ErrSyntax},
+	{"12345_", 0, ErrSyntax},
 }
 
 type parseInt64BaseTest struct {
@@ -144,6 +216,26 @@ var parseInt64BaseTests = []parseInt64BaseTest{
 	{"10", 16, 16, nil},
 	{"-123456789abcdef", 16, -0x123456789abcdef, nil},
 	{"7fffffffffffffff", 16, 1<<63 - 1, nil},
+
+	// underscores
+	{"-0x_1_2_3_4_5", 0, -0x12345, nil},
+	{"0x_1_2_3_4_5", 0, 0x12345, nil},
+	{"-_0x12345", 0, 0, ErrSyntax},
+	{"_-0x12345", 0, 0, ErrSyntax},
+	{"_0x12345", 0, 0, ErrSyntax},
+	{"0x__12345", 0, 0, ErrSyntax},
+	{"0x1__2345", 0, 0, ErrSyntax},
+	{"0x1234__5", 0, 0, ErrSyntax},
+	{"0x12345_", 0, 0, ErrSyntax},
+
+	{"-0_1_2_3_4_5", 0, -012345, nil}, // octal
+	{"0_1_2_3_4_5", 0, 012345, nil},   // octal
+	{"-_012345", 0, 0, ErrSyntax},
+	{"_-012345", 0, 0, ErrSyntax},
+	{"_012345", 0, 0, ErrSyntax},
+	{"0__12345", 0, 0, ErrSyntax},
+	{"01234__5", 0, 0, ErrSyntax},
+	{"012345_", 0, 0, ErrSyntax},
 }
 
 type parseUint32Test struct {
@@ -162,6 +254,11 @@ var parseUint32Tests = []parseUint32Test{
 	{"987654321", 987654321, nil},
 	{"4294967295", 1<<32 - 1, nil},
 	{"4294967296", 1<<32 - 1, ErrRange},
+	{"1_2_3_4_5", 0, ErrSyntax}, // base=10 so no underscores allowed
+	{"_12345", 0, ErrSyntax},
+	{"_12345", 0, ErrSyntax},
+	{"1__2345", 0, ErrSyntax},
+	{"12345_", 0, ErrSyntax},
 }
 
 type parseInt32Test struct {
@@ -190,6 +287,11 @@ var parseInt32Tests = []parseInt32Test{
 	{"-2147483648", -1 << 31, nil},
 	{"2147483649", 1<<31 - 1, ErrRange},
 	{"-2147483649", -1 << 31, ErrRange},
+	{"-1_2_3_4_5", 0, ErrSyntax}, // base=10 so no underscores allowed
+	{"-_12345", 0, ErrSyntax},
+	{"_12345", 0, ErrSyntax},
+	{"1__2345", 0, ErrSyntax},
+	{"12345_", 0, ErrSyntax},
 }
 
 type numErrorTest struct {
@@ -419,12 +521,22 @@ var parseBaseTests = []parseErrorTest{
 	{37, baseErrStub},
 }
 
+func equalError(a, b error) bool {
+	if a == nil {
+		return b == nil
+	}
+	if b == nil {
+		return a == nil
+	}
+	return a.Error() == b.Error()
+}
+
 func TestParseIntBitSize(t *testing.T) {
 	for i := range parseBitSizeTests {
 		test := &parseBitSizeTests[i]
 		testErr := test.errStub("ParseInt", test.arg)
 		_, err := ParseInt("0", 0, test.arg)
-		if !reflect.DeepEqual(testErr, err) {
+		if !equalError(testErr, err) {
 			t.Errorf("ParseInt(\"0\", 0, %v) = 0, %v want 0, %v",
 				test.arg, err, testErr)
 		}
@@ -436,7 +548,7 @@ func TestParseUintBitSize(t *testing.T) {
 		test := &parseBitSizeTests[i]
 		testErr := test.errStub("ParseUint", test.arg)
 		_, err := ParseUint("0", 0, test.arg)
-		if !reflect.DeepEqual(testErr, err) {
+		if !equalError(testErr, err) {
 			t.Errorf("ParseUint(\"0\", 0, %v) = 0, %v want 0, %v",
 				test.arg, err, testErr)
 		}
@@ -448,7 +560,7 @@ func TestParseIntBase(t *testing.T) {
 		test := &parseBaseTests[i]
 		testErr := test.errStub("ParseInt", test.arg)
 		_, err := ParseInt("0", test.arg, 0)
-		if !reflect.DeepEqual(testErr, err) {
+		if !equalError(testErr, err) {
 			t.Errorf("ParseInt(\"0\", %v, 0) = 0, %v want 0, %v",
 				test.arg, err, testErr)
 		}
@@ -460,7 +572,7 @@ func TestParseUintBase(t *testing.T) {
 		test := &parseBaseTests[i]
 		testErr := test.errStub("ParseUint", test.arg)
 		_, err := ParseUint("0", test.arg, 0)
-		if !reflect.DeepEqual(testErr, err) {
+		if !equalError(testErr, err) {
 			t.Errorf("ParseUint(\"0\", %v, 0) = 0, %v want 0, %v",
 				test.arg, err, testErr)
 		}
diff --git a/libgo/go/strconv/example_test.go b/libgo/go/strconv/example_test.go
index 2d1a2a9..50f6b20 100644
--- a/libgo/go/strconv/example_test.go
+++ b/libgo/go/strconv/example_test.go
@@ -222,10 +222,39 @@ func ExampleParseFloat() {
 	if s, err := strconv.ParseFloat(v, 64); err == nil {
 		fmt.Printf("%T, %v\n", s, s)
 	}
+	if s, err := strconv.ParseFloat("NaN", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	// ParseFloat is case insensitive
+	if s, err := strconv.ParseFloat("nan", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseFloat("inf", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseFloat("+Inf", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseFloat("-Inf", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseFloat("-0", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
+	if s, err := strconv.ParseFloat("+0", 32); err == nil {
+		fmt.Printf("%T, %v\n", s, s)
+	}
 
 	// Output:
 	// float64, 3.1415927410125732
 	// float64, 3.1415926535
+	// float64, NaN
+	// float64, NaN
+	// float64, +Inf
+	// float64, +Inf
+	// float64, -Inf
+	// float64, -0
+	// float64, 0
 }
 
 func ExampleParseInt() {
diff --git a/libgo/go/strconv/extfloat.go b/libgo/go/strconv/extfloat.go
index 32d3340..2a2dd7a 100644
--- a/libgo/go/strconv/extfloat.go
+++ b/libgo/go/strconv/extfloat.go
@@ -214,20 +214,9 @@ func (f *extFloat) Normalize() uint {
 // Multiply sets f to the product f*g: the result is correctly rounded,
 // but not normalized.
 func (f *extFloat) Multiply(g extFloat) {
-	fhi, flo := f.mant>>32, uint64(uint32(f.mant))
-	ghi, glo := g.mant>>32, uint64(uint32(g.mant))
-
-	// Cross products.
-	cross1 := fhi * glo
-	cross2 := flo * ghi
-
-	// f.mant*g.mant is fhi*ghi << 64 + (cross1+cross2) << 32 + flo*glo
-	f.mant = fhi*ghi + (cross1 >> 32) + (cross2 >> 32)
-	rem := uint64(uint32(cross1)) + uint64(uint32(cross2)) + ((flo * glo) >> 32)
+	hi, lo := bits.Mul64(f.mant, g.mant)
 	// Round up.
-	rem += (1 << 31)
-
-	f.mant += (rem >> 32)
+	f.mant = hi + (lo >> 63)
 	f.exp = f.exp + g.exp + 64
 }
 
diff --git a/libgo/go/strconv/ftoa.go b/libgo/go/strconv/ftoa.go
index a7ccbe6..8ce6ef3 100644
--- a/libgo/go/strconv/ftoa.go
+++ b/libgo/go/strconv/ftoa.go
@@ -32,12 +32,14 @@ var float64info = floatInfo{52, 11, -1023}
 // 'e' (-d.dddde±dd, a decimal exponent),
 // 'E' (-d.ddddE±dd, a decimal exponent),
 // 'f' (-ddd.dddd, no exponent),
-// 'g' ('e' for large exponents, 'f' otherwise), or
-// 'G' ('E' for large exponents, 'f' otherwise).
+// 'g' ('e' for large exponents, 'f' otherwise),
+// 'G' ('E' for large exponents, 'f' otherwise),
+// 'x' (-0xd.ddddp±ddd, a hexadecimal fraction and binary exponent), or
+// 'X' (-0Xd.ddddP±ddd, a hexadecimal fraction and binary exponent).
 //
 // The precision prec controls the number of digits (excluding the exponent)
-// printed by the 'e', 'E', 'f', 'g', and 'G' formats.
-// For 'e', 'E', and 'f' it is the number of digits after the decimal point.
+// printed by the 'e', 'E', 'f', 'g', 'G', 'x', and 'X' formats.
+// For 'e', 'E', 'f', 'x', and 'X', it is the number of digits after the decimal point.
 // For 'g' and 'G' it is the maximum number of significant digits (trailing
 // zeros are removed).
 // The special precision -1 uses the smallest number of digits
@@ -94,10 +96,13 @@ func genericFtoa(dst []byte, val float64, fmt byte, prec, bitSize int) []byte {
 	}
 	exp += flt.bias
 
-	// Pick off easy binary format.
+	// Pick off easy binary, hex formats.
 	if fmt == 'b' {
 		return fmtB(dst, neg, mant, exp, flt)
 	}
+	if fmt == 'x' || fmt == 'X' {
+		return fmtX(dst, prec, fmt, neg, mant, exp, flt)
+	}
 
 	if !optimize {
 		return bigFtoa(dst, prec, fmt, neg, mant, exp, flt)
@@ -284,39 +289,80 @@ func roundShortest(d *decimal, mant uint64, exp int, flt *floatInfo) {
 	// would round to the original mantissa and not the neighbors.
 	inclusive := mant%2 == 0
 
+	// As we walk the digits we want to know whether rounding up would fall
+	// within the upper bound. This is tracked by upperdelta:
+	//
+	// If upperdelta == 0, the digits of d and upper are the same so far.
+	//
+	// If upperdelta == 1, we saw a difference of 1 between d and upper on a
+	// previous digit and subsequently only 9s for d and 0s for upper.
+	// (Thus rounding up may fall outside the bound, if it is exclusive.)
+	//
+	// If upperdelta == 2, then the difference is greater than 1
+	// and we know that rounding up falls within the bound.
+	var upperdelta uint8
+
 	// Now we can figure out the minimum number of digits required.
 	// Walk along until d has distinguished itself from upper and lower.
-	for i := 0; i < d.nd; i++ {
+	for ui := 0; ; ui++ {
+		// lower, d, and upper may have the decimal points at different
+		// places. In this case upper is the longest, so we iterate from
+		// ui==0 and start li and mi at (possibly) -1.
+		mi := ui - upper.dp + d.dp
+		if mi >= d.nd {
+			break
+		}
+		li := ui - upper.dp + lower.dp
 		l := byte('0') // lower digit
-		if i < lower.nd {
-			l = lower.d[i]
+		if li >= 0 && li < lower.nd {
+			l = lower.d[li]
+		}
+		m := byte('0') // middle digit
+		if mi >= 0 {
+			m = d.d[mi]
 		}
-		m := d.d[i]    // middle digit
 		u := byte('0') // upper digit
-		if i < upper.nd {
-			u = upper.d[i]
+		if ui < upper.nd {
+			u = upper.d[ui]
 		}
 
 		// Okay to round down (truncate) if lower has a different digit
 		// or if lower is inclusive and is exactly the result of rounding
 		// down (i.e., and we have reached the final digit of lower).
-		okdown := l != m || inclusive && i+1 == lower.nd
+		okdown := l != m || inclusive && li+1 == lower.nd
 
+		switch {
+		case upperdelta == 0 && m+1 < u:
+			// Example:
+			// m = 12345xxx
+			// u = 12347xxx
+			upperdelta = 2
+		case upperdelta == 0 && m != u:
+			// Example:
+			// m = 12345xxx
+			// u = 12346xxx
+			upperdelta = 1
+		case upperdelta == 1 && (m != '9' || u != '0'):
+			// Example:
+			// m = 1234598x
+			// u = 1234600x
+			upperdelta = 2
+		}
 		// Okay to round up if upper has a different digit and either upper
 		// is inclusive or upper is bigger than the result of rounding up.
-		okup := m != u && (inclusive || m+1 < u || i+1 < upper.nd)
+		okup := upperdelta > 0 && (inclusive || upperdelta > 1 || ui+1 < upper.nd)
 
 		// If it's okay to do either, then round to the nearest one.
 		// If it's okay to do only one, do it.
 		switch {
 		case okdown && okup:
-			d.Round(i + 1)
+			d.Round(mi + 1)
 			return
 		case okdown:
-			d.RoundDown(i + 1)
+			d.RoundDown(mi + 1)
 			return
 		case okup:
-			d.RoundUp(i + 1)
+			d.RoundUp(mi + 1)
 			return
 		}
 	}
@@ -439,6 +485,89 @@ func fmtB(dst []byte, neg bool, mant uint64, exp int, flt *floatInfo) []byte {
 	return dst
 }
 
+// %x: -0x1.yyyyyyyyp±ddd or -0x0p+0. (y is hex digit, d is decimal digit)
+func fmtX(dst []byte, prec int, fmt byte, neg bool, mant uint64, exp int, flt *floatInfo) []byte {
+	if mant == 0 {
+		exp = 0
+	}
+
+	// Shift digits so leading 1 (if any) is at bit 1<<60.
+	mant <<= 60 - flt.mantbits
+	for mant != 0 && mant&(1<<60) == 0 {
+		mant <<= 1
+		exp--
+	}
+
+	// Round if requested.
+	if prec >= 0 && prec < 15 {
+		shift := uint(prec * 4)
+		extra := (mant << shift) & (1<<60 - 1)
+		mant >>= 60 - shift
+		if extra|(mant&1) > 1<<59 {
+			mant++
+		}
+		mant <<= 60 - shift
+		if mant&(1<<61) != 0 {
+			// Wrapped around.
+			mant >>= 1
+			exp++
+		}
+	}
+
+	hex := lowerhex
+	if fmt == 'X' {
+		hex = upperhex
+	}
+
+	// sign, 0x, leading digit
+	if neg {
+		dst = append(dst, '-')
+	}
+	dst = append(dst, '0', fmt, '0'+byte((mant>>60)&1))
+
+	// .fraction
+	mant <<= 4 // remove leading 0 or 1
+	if prec < 0 && mant != 0 {
+		dst = append(dst, '.')
+		for mant != 0 {
+			dst = append(dst, hex[(mant>>60)&15])
+			mant <<= 4
+		}
+	} else if prec > 0 {
+		dst = append(dst, '.')
+		for i := 0; i < prec; i++ {
+			dst = append(dst, hex[(mant>>60)&15])
+			mant <<= 4
+		}
+	}
+
+	// p±
+	ch := byte('P')
+	if fmt == lower(fmt) {
+		ch = 'p'
+	}
+	dst = append(dst, ch)
+	if exp < 0 {
+		ch = '-'
+		exp = -exp
+	} else {
+		ch = '+'
+	}
+	dst = append(dst, ch)
+
+	// dd or ddd or dddd
+	switch {
+	case exp < 100:
+		dst = append(dst, byte(exp/10)+'0', byte(exp%10)+'0')
+	case exp < 1000:
+		dst = append(dst, byte(exp/100)+'0', byte((exp/10)%10)+'0', byte(exp%10)+'0')
+	default:
+		dst = append(dst, byte(exp/1000)+'0', byte(exp/100)%10+'0', byte((exp/10)%10)+'0', byte(exp%10)+'0')
+	}
+
+	return dst
+}
+
 func min(a, b int) int {
 	if a < b {
 		return a
diff --git a/libgo/go/strconv/ftoa_test.go b/libgo/go/strconv/ftoa_test.go
index 1d3030b..755c986 100644
--- a/libgo/go/strconv/ftoa_test.go
+++ b/libgo/go/strconv/ftoa_test.go
@@ -30,9 +30,15 @@ var ftoatests = []ftoaTest{
 	{1, 'f', 5, "1.00000"},
 	{1, 'g', 5, "1"},
 	{1, 'g', -1, "1"},
+	{1, 'x', -1, "0x1p+00"},
+	{1, 'x', 5, "0x1.00000p+00"},
 	{20, 'g', -1, "20"},
+	{20, 'x', -1, "0x1.4p+04"},
 	{1234567.8, 'g', -1, "1.2345678e+06"},
+	{1234567.8, 'x', -1, "0x1.2d687cccccccdp+20"},
 	{200000, 'g', -1, "200000"},
+	{200000, 'x', -1, "0x1.86ap+17"},
+	{200000, 'X', -1, "0X1.86AP+17"},
 	{2000000, 'g', -1, "2e+06"},
 
 	// g conversion and zero suppression
@@ -50,6 +56,7 @@ var ftoatests = []ftoaTest{
 	{0, 'f', 5, "0.00000"},
 	{0, 'g', 5, "0"},
 	{0, 'g', -1, "0"},
+	{0, 'x', 5, "0x0.00000p+00"},
 
 	{-1, 'e', 5, "-1.00000e+00"},
 	{-1, 'f', 5, "-1.00000"},
@@ -100,7 +107,8 @@ var ftoatests = []ftoaTest{
 	{32, 'g', -1, "32"},
 	{32, 'g', 0, "3e+01"},
 
-	{100, 'x', -1, "%x"},
+	{100, 'x', -1, "0x1.9p+06"},
+	{100, 'y', -1, "%y"},
 
 	{math.NaN(), 'g', -1, "NaN"},
 	{-math.NaN(), 'g', -1, "NaN"},
@@ -128,6 +136,27 @@ var ftoatests = []ftoaTest{
 	// Issue 2625.
 	{383260575764816448, 'f', 0, "383260575764816448"},
 	{383260575764816448, 'g', -1, "3.8326057576481645e+17"},
+
+	// Issue 29491.
+	{498484681984085570, 'f', -1, "498484681984085570"},
+	{-5.8339553793802237e+23, 'g', -1, "-5.8339553793802237e+23"},
+
+	// rounding
+	{2.275555555555555, 'x', -1, "0x1.23456789abcdep+01"},
+	{2.275555555555555, 'x', 0, "0x1p+01"},
+	{2.275555555555555, 'x', 2, "0x1.23p+01"},
+	{2.275555555555555, 'x', 16, "0x1.23456789abcde000p+01"},
+	{2.275555555555555, 'x', 21, "0x1.23456789abcde00000000p+01"},
+	{2.2755555510520935, 'x', -1, "0x1.2345678p+01"},
+	{2.2755555510520935, 'x', 6, "0x1.234568p+01"},
+	{2.275555431842804, 'x', -1, "0x1.2345668p+01"},
+	{2.275555431842804, 'x', 6, "0x1.234566p+01"},
+	{3.999969482421875, 'x', -1, "0x1.ffffp+01"},
+	{3.999969482421875, 'x', 4, "0x1.ffffp+01"},
+	{3.999969482421875, 'x', 3, "0x1.000p+02"},
+	{3.999969482421875, 'x', 2, "0x1.00p+02"},
+	{3.999969482421875, 'x', 1, "0x1.0p+02"},
+	{3.999969482421875, 'x', 0, "0x1p+02"},
 }
 
 func TestFtoa(t *testing.T) {
diff --git a/libgo/go/strconv/isprint.go b/libgo/go/strconv/isprint.go
index f537ba4..a8dfdb2 100644
--- a/libgo/go/strconv/isprint.go
+++ b/libgo/go/strconv/isprint.go
@@ -6,7 +6,7 @@
 
 package strconv
 
-// (456+140+86)*2 + (396)*4 = 2948 bytes
+// (448+137+90)*2 + (418)*4 = 3022 bytes
 
 var isPrint16 = []uint16{
 	0x0020, 0x007e,
@@ -16,17 +16,17 @@ var isPrint16 = []uint16{
 	0x0559, 0x058a,
 	0x058d, 0x05c7,
 	0x05d0, 0x05ea,
-	0x05f0, 0x05f4,
+	0x05ef, 0x05f4,
 	0x0606, 0x061b,
 	0x061e, 0x070d,
 	0x0710, 0x074a,
 	0x074d, 0x07b1,
 	0x07c0, 0x07fa,
-	0x0800, 0x082d,
+	0x07fd, 0x082d,
 	0x0830, 0x085b,
 	0x085e, 0x086a,
 	0x08a0, 0x08bd,
-	0x08d4, 0x098c,
+	0x08d3, 0x098c,
 	0x098f, 0x0990,
 	0x0993, 0x09b2,
 	0x09b6, 0x09b9,
@@ -35,7 +35,7 @@ var isPrint16 = []uint16{
 	0x09cb, 0x09ce,
 	0x09d7, 0x09d7,
 	0x09dc, 0x09e3,
-	0x09e6, 0x09fd,
+	0x09e6, 0x09fe,
 	0x0a01, 0x0a0a,
 	0x0a0f, 0x0a10,
 	0x0a13, 0x0a39,
@@ -44,7 +44,7 @@ var isPrint16 = []uint16{
 	0x0a4b, 0x0a4d,
 	0x0a51, 0x0a51,
 	0x0a59, 0x0a5e,
-	0x0a66, 0x0a75,
+	0x0a66, 0x0a76,
 	0x0a81, 0x0ab9,
 	0x0abc, 0x0acd,
 	0x0ad0, 0x0ad0,
@@ -126,7 +126,7 @@ var isPrint16 = []uint16{
 	0x17f0, 0x17f9,
 	0x1800, 0x180d,
 	0x1810, 0x1819,
-	0x1820, 0x1877,
+	0x1820, 0x1878,
 	0x1880, 0x18aa,
 	0x18b0, 0x18f5,
 	0x1900, 0x192b,
@@ -149,7 +149,8 @@ var isPrint16 = []uint16{
 	0x1bfc, 0x1c37,
 	0x1c3b, 0x1c49,
 	0x1c4d, 0x1c88,
-	0x1cc0, 0x1cc7,
+	0x1c90, 0x1cba,
+	0x1cbd, 0x1cc7,
 	0x1cd0, 0x1cf9,
 	0x1d00, 0x1f15,
 	0x1f18, 0x1f1d,
@@ -170,38 +171,33 @@ var isPrint16 = []uint16{
 	0x2440, 0x244a,
 	0x2460, 0x2b73,
 	0x2b76, 0x2b95,
-	0x2b98, 0x2bb9,
-	0x2bbd, 0x2bd2,
-	0x2bec, 0x2bef,
-	0x2c00, 0x2cf3,
+	0x2b98, 0x2cf3,
 	0x2cf9, 0x2d27,
 	0x2d2d, 0x2d2d,
 	0x2d30, 0x2d67,
 	0x2d6f, 0x2d70,
 	0x2d7f, 0x2d96,
-	0x2da0, 0x2e49,
+	0x2da0, 0x2e4e,
 	0x2e80, 0x2ef3,
 	0x2f00, 0x2fd5,
 	0x2ff0, 0x2ffb,
 	0x3001, 0x3096,
 	0x3099, 0x30ff,
-	0x3105, 0x312e,
-	0x3131, 0x31ba,
+	0x3105, 0x31ba,
 	0x31c0, 0x31e3,
 	0x31f0, 0x4db5,
-	0x4dc0, 0x9fea,
+	0x4dc0, 0x9fef,
 	0xa000, 0xa48c,
 	0xa490, 0xa4c6,
 	0xa4d0, 0xa62b,
 	0xa640, 0xa6f7,
-	0xa700, 0xa7b7,
+	0xa700, 0xa7b9,
 	0xa7f7, 0xa82b,
 	0xa830, 0xa839,
 	0xa840, 0xa877,
 	0xa880, 0xa8c5,
 	0xa8ce, 0xa8d9,
-	0xa8e0, 0xa8fd,
-	0xa900, 0xa953,
+	0xa8e0, 0xa953,
 	0xa95f, 0xa97c,
 	0xa980, 0xa9d9,
 	0xa9de, 0xaa36,
@@ -245,8 +241,6 @@ var isNotPrint16 = []uint16{
 	0x038d,
 	0x03a2,
 	0x0530,
-	0x0560,
-	0x0588,
 	0x0590,
 	0x06dd,
 	0x083f,
@@ -283,14 +277,12 @@ var isNotPrint16 = []uint16{
 	0x0b9b,
 	0x0b9d,
 	0x0bc9,
-	0x0c04,
 	0x0c0d,
 	0x0c11,
 	0x0c29,
 	0x0c45,
 	0x0c49,
 	0x0c57,
-	0x0c84,
 	0x0c8d,
 	0x0c91,
 	0x0ca9,
@@ -350,6 +342,7 @@ var isNotPrint16 = []uint16{
 	0x1ff5,
 	0x208f,
 	0x2bc9,
+	0x2bff,
 	0x2c2f,
 	0x2c5f,
 	0x2d26,
@@ -363,10 +356,10 @@ var isNotPrint16 = []uint16{
 	0x2ddf,
 	0x2e9a,
 	0x3040,
+	0x3130,
 	0x318f,
 	0x321f,
 	0x32ff,
-	0xa7af,
 	0xa9ce,
 	0xa9ff,
 	0xab27,
@@ -421,9 +414,9 @@ var isPrint32 = []uint32{
 	0x010980, 0x0109b7,
 	0x0109bc, 0x0109cf,
 	0x0109d2, 0x010a06,
-	0x010a0c, 0x010a33,
+	0x010a0c, 0x010a35,
 	0x010a38, 0x010a3a,
-	0x010a3f, 0x010a47,
+	0x010a3f, 0x010a48,
 	0x010a50, 0x010a58,
 	0x010a60, 0x010a9f,
 	0x010ac0, 0x010ae6,
@@ -437,14 +430,17 @@ var isPrint32 = []uint32{
 	0x010c00, 0x010c48,
 	0x010c80, 0x010cb2,
 	0x010cc0, 0x010cf2,
-	0x010cfa, 0x010cff,
+	0x010cfa, 0x010d27,
+	0x010d30, 0x010d39,
 	0x010e60, 0x010e7e,
+	0x010f00, 0x010f27,
+	0x010f30, 0x010f59,
 	0x011000, 0x01104d,
 	0x011052, 0x01106f,
 	0x01107f, 0x0110c1,
 	0x0110d0, 0x0110e8,
 	0x0110f0, 0x0110f9,
-	0x011100, 0x011143,
+	0x011100, 0x011146,
 	0x011150, 0x011176,
 	0x011180, 0x0111cd,
 	0x0111d0, 0x0111f4,
@@ -454,8 +450,7 @@ var isPrint32 = []uint32{
 	0x0112f0, 0x0112f9,
 	0x011300, 0x01130c,
 	0x01130f, 0x011310,
-	0x011313, 0x011339,
-	0x01133c, 0x011344,
+	0x011313, 0x011344,
 	0x011347, 0x011348,
 	0x01134b, 0x01134d,
 	0x011350, 0x011350,
@@ -463,7 +458,7 @@ var isPrint32 = []uint32{
 	0x01135d, 0x011363,
 	0x011366, 0x01136c,
 	0x011370, 0x011374,
-	0x011400, 0x01145d,
+	0x011400, 0x01145e,
 	0x011480, 0x0114c7,
 	0x0114d0, 0x0114d9,
 	0x011580, 0x0115b5,
@@ -473,9 +468,10 @@ var isPrint32 = []uint32{
 	0x011660, 0x01166c,
 	0x011680, 0x0116b7,
 	0x0116c0, 0x0116c9,
-	0x011700, 0x011719,
+	0x011700, 0x01171a,
 	0x01171d, 0x01172b,
 	0x011730, 0x01173f,
+	0x011800, 0x01183b,
 	0x0118a0, 0x0118f2,
 	0x0118ff, 0x0118ff,
 	0x011a00, 0x011a47,
@@ -489,6 +485,9 @@ var isPrint32 = []uint32{
 	0x011d00, 0x011d36,
 	0x011d3a, 0x011d47,
 	0x011d50, 0x011d59,
+	0x011d60, 0x011d98,
+	0x011da0, 0x011da9,
+	0x011ee0, 0x011ef8,
 	0x012000, 0x012399,
 	0x012400, 0x012474,
 	0x012480, 0x012543,
@@ -502,11 +501,12 @@ var isPrint32 = []uint32{
 	0x016b00, 0x016b45,
 	0x016b50, 0x016b77,
 	0x016b7d, 0x016b8f,
+	0x016e40, 0x016e9a,
 	0x016f00, 0x016f44,
 	0x016f50, 0x016f7e,
 	0x016f8f, 0x016f9f,
 	0x016fe0, 0x016fe1,
-	0x017000, 0x0187ec,
+	0x017000, 0x0187f1,
 	0x018800, 0x018af2,
 	0x01b000, 0x01b11e,
 	0x01b170, 0x01b2fb,
@@ -520,8 +520,9 @@ var isPrint32 = []uint32{
 	0x01d129, 0x01d172,
 	0x01d17b, 0x01d1e8,
 	0x01d200, 0x01d245,
+	0x01d2e0, 0x01d2f3,
 	0x01d300, 0x01d356,
-	0x01d360, 0x01d371,
+	0x01d360, 0x01d378,
 	0x01d400, 0x01d49f,
 	0x01d4a2, 0x01d4a2,
 	0x01d4a5, 0x01d4a6,
@@ -538,6 +539,7 @@ var isPrint32 = []uint32{
 	0x01e900, 0x01e94a,
 	0x01e950, 0x01e959,
 	0x01e95e, 0x01e95f,
+	0x01ec71, 0x01ecb4,
 	0x01ee00, 0x01ee24,
 	0x01ee27, 0x01ee3b,
 	0x01ee42, 0x01ee42,
@@ -560,20 +562,22 @@ var isPrint32 = []uint32{
 	0x01f260, 0x01f265,
 	0x01f300, 0x01f6d4,
 	0x01f6e0, 0x01f6ec,
-	0x01f6f0, 0x01f6f8,
+	0x01f6f0, 0x01f6f9,
 	0x01f700, 0x01f773,
-	0x01f780, 0x01f7d4,
+	0x01f780, 0x01f7d8,
 	0x01f800, 0x01f80b,
 	0x01f810, 0x01f847,
 	0x01f850, 0x01f859,
 	0x01f860, 0x01f887,
 	0x01f890, 0x01f8ad,
 	0x01f900, 0x01f90b,
-	0x01f910, 0x01f94c,
-	0x01f950, 0x01f96b,
-	0x01f980, 0x01f997,
-	0x01f9c0, 0x01f9c0,
-	0x01f9d0, 0x01f9e6,
+	0x01f910, 0x01f970,
+	0x01f973, 0x01f976,
+	0x01f97a, 0x01f9a2,
+	0x01f9b0, 0x01f9b9,
+	0x01f9c0, 0x01f9c2,
+	0x01f9d0, 0x01f9ff,
+	0x01fa60, 0x01fa6d,
 	0x020000, 0x02a6d6,
 	0x02a700, 0x02b734,
 	0x02b740, 0x02b81d,
@@ -609,9 +613,9 @@ var isNotPrint32 = []uint16{ // add 0x10000 to each entry
 	0x1329,
 	0x1331,
 	0x1334,
+	0x133a,
 	0x145a,
 	0x145c,
-	0x1a9d,
 	0x1c09,
 	0x1c37,
 	0x1ca8,
@@ -619,6 +623,10 @@ var isNotPrint32 = []uint16{ // add 0x10000 to each entry
 	0x1d0a,
 	0x1d3b,
 	0x1d3e,
+	0x1d66,
+	0x1d69,
+	0x1d8f,
+	0x1d92,
 	0x246f,
 	0x6a5f,
 	0x6b5a,
@@ -668,8 +676,8 @@ var isNotPrint32 = []uint16{ // add 0x10000 to each entry
 	0xeeaa,
 	0xf0c0,
 	0xf0d0,
-	0xf12f,
 	0xf93f,
+	0xf97b,
 }
 
 // isGraphic lists the graphic runes not matched by IsPrint.
diff --git a/libgo/go/strconv/quote.go b/libgo/go/strconv/quote.go
index 6cd2f93..b50496a 100644
--- a/libgo/go/strconv/quote.go
+++ b/libgo/go/strconv/quote.go
@@ -11,7 +11,10 @@ import (
 	"unicode/utf8"
 )
 
-const lowerhex = "0123456789abcdef"
+const (
+	lowerhex = "0123456789abcdef"
+	upperhex = "0123456789ABCDEF"
+)
 
 func quoteWith(s string, quote byte, ASCIIonly, graphicOnly bool) string {
 	return string(appendQuotedWith(make([]byte, 0, 3*len(s)/2), s, quote, ASCIIonly, graphicOnly))
@@ -22,6 +25,13 @@ func quoteRuneWith(r rune, quote byte, ASCIIonly, graphicOnly bool) string {
 }
 
 func appendQuotedWith(buf []byte, s string, quote byte, ASCIIonly, graphicOnly bool) []byte {
+	// Often called with big strings, so preallocate. If there's quoting,
+	// this is conservative but still helps a lot.
+	if cap(buf)-len(buf) < len(s) {
+		nBuf := make([]byte, len(buf), len(buf)+1+len(s)+1)
+		copy(nBuf, buf)
+		buf = nBuf
+	}
 	buf = append(buf, quote)
 	for width := 0; len(s) > 0; s = s[width:] {
 		r := rune(s[0])
diff --git a/libgo/go/strconv/strconv_test.go b/libgo/go/strconv/strconv_test.go
index ebec0cc..7619f90 100644
--- a/libgo/go/strconv/strconv_test.go
+++ b/libgo/go/strconv/strconv_test.go
@@ -30,6 +30,9 @@ var (
 			AppendFloat(localBuf[:0], 1.23, 'g', 5, 64)
 		}},
 		{0, `AppendFloat(globalBuf[:0], 1.23, 'g', 5, 64)`, func() { AppendFloat(globalBuf[:0], 1.23, 'g', 5, 64) }},
+		// In practice we see 7 for the next one, but allow some slop.
+		// Before pre-allocation in appendQuotedWith, we saw 39.
+		{10, `AppendQuoteToASCII(nil, oneMB)`, func() { AppendQuoteToASCII(nil, string(oneMB)) }},
 		{0, `ParseFloat("123.45", 64)`, func() { ParseFloat("123.45", 64) }},
 		{0, `ParseFloat("123.456789123456789", 64)`, func() { ParseFloat("123.456789123456789", 64) }},
 		{0, `ParseFloat("1.000000000000000111022302462515654042363166809082031251", 64)`, func() {
@@ -41,6 +44,8 @@ var (
 	}
 )
 
+var oneMB []byte // Will be allocated to 1MB of random data by TestCountMallocs.
+
 func TestCountMallocs(t *testing.T) {
 	if runtime.Compiler == "gccgo" {
 		t.Skip("skipping on gccgo until escape analysis is turned on")
@@ -51,6 +56,11 @@ func TestCountMallocs(t *testing.T) {
 	if runtime.GOMAXPROCS(0) > 1 {
 		t.Skip("skipping; GOMAXPROCS>1")
 	}
+	// Allocate a big messy buffer for AppendQuoteToASCII's test.
+	oneMB = make([]byte, 1e6)
+	for i := range oneMB {
+		oneMB[i] = byte(i)
+	}
 	for _, mt := range mallocTest {
 		allocs := testing.AllocsPerRun(100, mt.fn)
 		if max := float64(mt.count); allocs > max {