perf: optimize math.Int.Size for small values (#17497)

math/CHANGELOG.md

@@ -34,6 +34,12 @@ Ref: https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.j
 
 # Changelog
 
+## [Unreleased]
+
+### Improvements
+
+* [#17497](https://github.com/cosmos/cosmos-sdk/pull/17497) Optimize math.Int.Size for values that fit in 53 bits.
+
 ## [math/v1.1.2](https://github.com/cosmos/cosmos-sdk/releases/tag/math/v1.1.2) - 2023-08-21
 
 ### Bug Fixes

math/fuzz_test.go

@@ -22,3 +22,15 @@ func FuzzLegacyNewDecFromStr(f *testing.F) {
 		}
 	})
 }
+
+func FuzzSmallIntSize(f *testing.F) {
+	f.Add(int64(2<<53 - 1))
+	f.Add(-int64(2<<53 - 1))
+	f.Fuzz(func(t *testing.T, input int64) {
+		i := NewInt(input)
+		exp, _ := i.Marshal()
+		if i.Size() != len(exp) {
+			t.Fatalf("input %d: i.Size()=%d, len(input)=%d", input, i.Size(), len(exp))
+		}
+	})
+}

math/int.go

@@ -4,6 +4,7 @@ import (
 	"encoding"
 	"encoding/json"
 	"fmt"
+	stdmath "math"
 	"math/big"
 	"strings"
 	"sync"
@@ -429,6 +430,24 @@ func (i *Int) Unmarshal(data []byte) error {
 
 // Size implements the gogo proto custom type interface.
 func (i *Int) Size() int {
+	if i.i == nil {
+		return 1
+	}
+	// A float64 can store 52 bits exactly, which allows us to use
+	// math.Log10 to compute the size fast and garbage free.
+	if i.i.BitLen() <= 52 {
+		i64 := i.i.Int64()
+		if i64 == 0 {
+			return 1
+		}
+		size := 0
+		if i64 < 0 {
+			i64 = -i64
+			size++
+		}
+		return size + 1 + int(stdmath.Log10(float64(i64)))
+	}
+	// Slow path.
 	bz, _ := i.Marshal()
 	return len(bz)
 }

math/int_test.go

@@ -592,14 +592,16 @@ func TestNewIntFromString(t *testing.T) {
 }
 
 func BenchmarkIntSize(b *testing.B) {
+	var tests []math.Int
+	for _, st := range sizeTests {
+		ii, _ := math.NewIntFromString(st.s)
+		tests = append(tests, ii)
+	}
+	b.ResetTimer()
 	b.ReportAllocs()
 	for i := 0; i < b.N; i++ {
-		for _, st := range sizeTests {
-			ii, _ := math.NewIntFromString(st.s)
+		for _, ii := range tests {
 			got := ii.Size()
-			if got != st.want {
-				b.Errorf("%q:: got=%d, want=%d", st.s, got, st.want)
-			}
 			sink = got
 		}
 	}