Revert "math: add Compare and Compare32"

This reverts CL 467515. Now that we have cmp.Compare,
we don't need math.Compare or math.Compare32 after all.

For #56491
Fixes #60519

Change-Id: I8ed33464adfc6d69bd6b328edb26aa2ee3d234d9
Reviewed-on: https://go-review.googlesource.com/c/go/+/499416
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Eli Bendersky <eliben@google.com>

api/next/56491.txt

@@ -1,2 +0,0 @@
-pkg math, func Compare(float64, float64) int #56491
-pkg math, func Compare32(float32, float32) int #56491

src/math/all_test.go

@@ -2094,67 +2094,6 @@ var sqrt32 = []float32{
 	-5.0106036182710749e+00,
 }
 
-type compareTest[F float32 | float64] struct {
-	x, y F
-	want int
-}
-
-func compareCasesFloat64() []compareTest[float64] {
-	zero, nan, inf := 0.0, NaN(), Inf(0)
-
-	// construct -NaN manually from its bit representation,
-	// since IEEE doesn't mandate negate(NaN) change the sign bit
-	unegnan := Float64bits(nan)
-	unegnan ^= 1 << 63
-	negnan := Float64frombits(unegnan)
-	return []compareTest[float64]{
-		{negnan, -inf, -1},
-		{-inf, negnan, 1},
-		{-inf, -Pi, -1},
-		{-Pi, -inf, 1},
-		{-Pi, -zero, -1},
-		{-zero, -Pi, 1},
-		{-zero, 0, -1},
-		{0, -zero, 1},
-		{0, Pi, -1},
-		{Pi, 0, 1},
-		{Pi, inf, -1},
-		{inf, Pi, 1},
-		{inf, nan, -1},
-		{nan, inf, 1},
-		{Pi, Pi, 0},
-		{negnan, negnan, 0},
-	}
-}
-
-func compareCasesFloat32() []compareTest[float32] {
-	zero, nan, inf := float32(0.0), float32(NaN()), float32(Inf(0))
-
-	// construct -NaN manually from its bit representation,
-	// since IEEE doesn't mandate negate(NaN) change the sign bit
-	unegnan := Float32bits(nan)
-	unegnan ^= 1 << 31
-	negnan := Float32frombits(unegnan)
-	return []compareTest[float32]{
-		{negnan, -inf, -1},
-		{-inf, negnan, 1},
-		{-inf, -Pi, -1},
-		{-Pi, -inf, 1},
-		{-Pi, -zero, -1},
-		{-zero, -Pi, 1},
-		{-zero, 0, -1},
-		{0, -zero, 1},
-		{0, Pi, -1},
-		{Pi, 0, 1},
-		{Pi, inf, -1},
-		{inf, Pi, 1},
-		{inf, nan, -1},
-		{nan, inf, 1},
-		{Pi, Pi, 0},
-		{negnan, negnan, 0},
-	}
-}
-
 func tolerance(a, b, e float64) bool {
 	// Multiplying by e here can underflow denormal values to zero.
 	// Check a==b so that at least if a and b are small and identical
@@ -2322,22 +2261,6 @@ func TestCeil(t *testing.T) {
 	}
 }
 
-func TestCompare(t *testing.T) {
-	// -NaN < -∞ < -3.14 < -0 < 0 < 3.14 < ∞ < NaN
-	for _, c := range compareCasesFloat64() {
-		cmp := Compare(c.x, c.y)
-		if cmp != c.want {
-			t.Errorf("Compare(%v, %v) = %d, want %v", c.x, c.y, cmp, c.want)
-		}
-	}
-	for _, c := range compareCasesFloat32() {
-		cmp := Compare32(c.x, c.y)
-		if cmp != c.want {
-			t.Errorf("Compare32(%v, %v) = %d, want %v", c.x, c.y, cmp, c.want)
-		}
-	}
-}
-
 func TestCopysign(t *testing.T) {
 	for i := 0; i < len(vf); i++ {
 		if f := Copysign(vf[i], -1); copysign[i] != f {
@@ -3397,23 +3320,6 @@ func BenchmarkCeil(b *testing.B) {
 	GlobalF = x
 }
 
-func BenchmarkCompare(b *testing.B) {
-	x := 0
-	for i := 0; i < b.N; i++ {
-		x = Compare(GlobalF, 1.5)
-	}
-	GlobalI = x
-}
-
-func BenchmarkCompare32(b *testing.B) {
-	x := 0
-	globalF32 := float32(GlobalF)
-	for i := 0; i < b.N; i++ {
-		x = Compare32(globalF32, 1.5)
-	}
-	GlobalI = x
-}
-
 var copysignNeg = -1.0
 
 func BenchmarkCopysign(b *testing.B) {

src/math/compare.go

@@ -1,53 +0,0 @@
-// Copyright 2023 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.
-
-package math
-
-func sign[I int32 | int64](a, b I) int {
-	if a < b {
-		return -1
-	}
-	if a > b {
-		return 1
-	}
-	return 0
-}
-
-// Compare compares a and b such that
-// -NaN is ordered before any other value,
-// +NaN is ordered after any other value,
-// and -0 is ordered before +0.
-// In other words, it defines a total order over floats
-// (according to the total-ordering predicate in IEEE-754, section 5.10).
-// It returns 0 if a == b, -1 if a < b, and +1 if a > b.
-func Compare(a, b float64) int {
-	// Perform a bitwise comparison (a < b) by casting the float64s into an int64s.
-	x := int64(Float64bits(a))
-	y := int64(Float64bits(b))
-
-	// If a and b are both negative, flip the comparison so that we check a > b.
-	if x < 0 && y < 0 {
-		return sign(y, x)
-	}
-	return sign(x, y)
-}
-
-// Compare32 compares a and b such that
-// -NaN is ordered before any other value,
-// +NaN is ordered after any other value,
-// and -0 is ordered before +0.
-// In other words, it defines a total order over floats
-// (according to the total-ordering predicate in IEEE-754, section 5.10).
-// It returns 0 if a == b, -1 if a < b, and +1 if a > b.
-func Compare32(a, b float32) int {
-	// Perform a bitwise comparison (a < b) by casting the float32s into an int32s.
-	x := int32(Float32bits(a))
-	y := int32(Float32bits(b))
-
-	// If a and b are both negative, flip the comparison so that we check a > b.
-	if x < 0 && y < 0 {
-		return sign(y, x)
-	}
-	return sign(x, y)
-}