From 14e99eab84426fede2d56ee2076ec25c5d729e73 Mon Sep 17 00:00:00 2001
From: Shenghui Wu <793703860@qq.com>
Date: Wed, 20 Nov 2024 13:19:57 +0800
Subject: [PATCH] Revert "util: fix codec for negative zero (#57343)" (#57525)

ref pingcap/tidb#57500
---
 pkg/util/codec/codec_test.go                  | 19 -------------------
 pkg/util/codec/float.go                       | 10 +---------
 .../r/expression/issues.result                |  6 ------
 .../integrationtest/t/expression/issues.test  |  6 ------
 4 files changed, 1 insertion(+), 40 deletions(-)

diff --git a/pkg/util/codec/codec_test.go b/pkg/util/codec/codec_test.go
index 1e0222233605e..6abc1c382c16f 100644
--- a/pkg/util/codec/codec_test.go
+++ b/pkg/util/codec/codec_test.go
@@ -1333,22 +1333,3 @@ func TestDatumHashEquals(t *testing.T) {
 	require.NotEqual(t, hasher1.Sum64(), hasher2.Sum64())
 	require.False(t, tests[len(tests)-1].d1.Equals(tests[len(tests)-1].d2))
 }
-
-func TestEncodeFloatForNegativeZero(t *testing.T) {
-	floatNum := 0.0
-	floatNum = -floatNum
-
-	b := EncodeFloat(nil, floatNum)
-	_, v, err := DecodeFloat(b)
-	require.NoError(t, err)
-	require.Equal(t, floatNum, v)
-	require.Equal(t, math.Signbit(floatNum), math.Signbit(v))
-	require.Equal(t, math.Atan2(0, v), math.Pi)
-
-	b = EncodeFloatDesc(nil, floatNum)
-	_, v, err = DecodeFloatDesc(b)
-	require.NoError(t, err)
-	require.Equal(t, floatNum, v)
-	require.Equal(t, math.Signbit(floatNum), math.Signbit(v))
-	require.Equal(t, math.Atan2(0, v), math.Pi)
-}
diff --git a/pkg/util/codec/float.go b/pkg/util/codec/float.go
index 9301db3e93ca0..df8d697463cbe 100644
--- a/pkg/util/codec/float.go
+++ b/pkg/util/codec/float.go
@@ -22,17 +22,9 @@ import (
 
 func encodeFloatToCmpUint64(f float64) uint64 {
 	u := math.Float64bits(f)
-	// Check the sign bit (the highest bit in the IEEE 754 representation).
-	// If the sign bit is 0, the number is non-negative (+0 is considered non-negative).
-	if u&signMask == 0 {
-		// For non-negative numbers (+0 included), set the sign bit to 1.
-		// This ensures non-negative numbers are ordered after negative numbers
-		// when compared as unsigned integers.
+	if f >= 0 {
 		u |= signMask
 	} else {
-		// For negative numbers (-0 included), invert all bits.
-		// This reorders negative numbers so that the smallest (closest to 0)
-		// has the smallest encoded value, and the most negative has the largest.
 		u = ^u
 	}
 	return u
diff --git a/tests/integrationtest/r/expression/issues.result b/tests/integrationtest/r/expression/issues.result
index 0a6bbf58f7988..f9d88b654e683 100644
--- a/tests/integrationtest/r/expression/issues.result
+++ b/tests/integrationtest/r/expression/issues.result
@@ -3230,12 +3230,6 @@ INSERT INTO test.t VALUES (1234567890123456);
 SELECT IFNULL(id, 'abcdef') FROM test.t;
 IFNULL(id, 'abcdef')
 1234567890123456
-DROP TABLE IF EXISTS test.t;
-CREATE TABLE test.t (c0 decimal(10,0));
-INSERT INTO test.t VALUES (0);
-SELECT c0 FROM test.t WHERE CAST(ATAN2(((t.c0) IS NULL), (- (''))) AS TIME);
-c0
-0
 drop table if exists test.t;
 create table test.t(a double);
 insert into test.t values('20000102030405.0078125');
diff --git a/tests/integrationtest/t/expression/issues.test b/tests/integrationtest/t/expression/issues.test
index 28dfc33368890..3eb6bcb0ead50 100644
--- a/tests/integrationtest/t/expression/issues.test
+++ b/tests/integrationtest/t/expression/issues.test
@@ -2183,12 +2183,6 @@ CREATE TABLE test.t (id bigint(11) UNSIGNED PRIMARY KEY);
 INSERT INTO test.t VALUES (1234567890123456);
 SELECT IFNULL(id, 'abcdef') FROM test.t;
 
-# TestIssue41878
-DROP TABLE IF EXISTS test.t;
-CREATE TABLE test.t (c0 decimal(10,0));
-INSERT INTO test.t VALUES (0);
-SELECT c0 FROM test.t WHERE CAST(ATAN2(((t.c0) IS NULL), (- (''))) AS TIME);
-
 # TestIssue56339
 drop table if exists test.t;
 create table test.t(a double);