perf(gnolang): improve print and println performance (gnolang#3952)

This change is the result of seeing print/println being reported in bugs
as needing gas metering but on examination, noticed that the code causes
a RAM and CPU bloat, so this makes an improvement in all dimensions by
invoking:
* io.WriteString(m.Output, segments) instead of
m.Output.Write([]byte(segments))
* in cases where `!debug`, we don't need to construct the concatenated 
  string delimited by " " and can instead write the Sprint-ed string 
segments as we encounter them

```shell
$ benchstat before_println.txt after_println3.txt
name          old time/op    new time/op    delta
GnoPrintln-8    1.94ms ± 2%    1.86ms ± 4%   -4.02%  (p=0.001 n=9+9)

name          old alloc/op   new alloc/op   delta
GnoPrintln-8    1.92MB ± 0%    1.81MB ± 0%   -5.92%  (p=0.000 n=10+10)

name          old allocs/op  new allocs/op  delta
GnoPrintln-8     19.0k ± 0%     16.0k ± 0%  -15.76%  (p=0.002 n=8+10)
```

Fixes gnolang#3951

---------

Co-authored-by: Morgan Bazalgette <[email protected]>

Author: odeke-em

gnovm/pkg/gnolang/machine_test.go

@@ -9,7 +9,6 @@ import (
 	"github.com/gnolang/gno/tm2/pkg/store/dbadapter"
 	"github.com/gnolang/gno/tm2/pkg/store/iavl"
 	stypes "github.com/gnolang/gno/tm2/pkg/store/types"
-	"github.com/google/go-cmp/cmp"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -109,9 +108,7 @@ func TestMachineString(t *testing.T) {
 	for _, tt := range cases {
 		t.Run(tt.name, func(t *testing.T) {
 			got := tt.in.String()
-			if diff := cmp.Diff(got, tt.want); diff != "" {
-				t.Fatalf("Mismatch: got - want +\n%s", diff)
-			}
+			assert.Equal(t, tt.want, got)
 		})
 	}
 }

gnovm/pkg/gnolang/uverse.go

@@ -1,8 +1,9 @@
 package gnolang
 
 import (
+	"bytes"
 	"fmt"
-	"strings"
+	"io"
 
 	bm "github.com/gnolang/gno/gnovm/pkg/benchops"
 )
@@ -708,6 +709,7 @@ func makeUverseNode() {
 			return
 		},
 	)
+
 	// NOTE: panic is its own statement type, and is not defined as a function.
 	defNative("print",
 		Flds( // params
@@ -716,18 +718,7 @@ func makeUverseNode() {
 		nil, // results
 		func(m *Machine) {
 			arg0 := m.LastBlock().GetParams1()
-			xv := arg0
-			xvl := xv.TV.GetLength()
-			ss := make([]string, xvl)
-			for i := 0; i < xvl; i++ {
-				ev := xv.TV.GetPointerAtIndexInt(m.Store, i).Deref()
-				ss[i] = ev.Sprint(m)
-			}
-			rs := strings.Join(ss, " ")
-			if debug {
-				print(rs)
-			}
-			m.Output.Write([]byte(rs))
+			uversePrint(m, arg0, false)
 		},
 	)
 	defNative("println",
@@ -737,18 +728,7 @@ func makeUverseNode() {
 		nil, // results
 		func(m *Machine) {
 			arg0 := m.LastBlock().GetParams1()
-			xv := arg0
-			xvl := xv.TV.GetLength()
-			ss := make([]string, xvl)
-			for i := 0; i < xvl; i++ {
-				ev := xv.TV.GetPointerAtIndexInt(m.Store, i).Deref()
-				ss[i] = ev.Sprint(m)
-			}
-			rs := strings.Join(ss, " ") + "\n"
-			if debug {
-				println("DEBUG/stdout: " + rs)
-			}
-			m.Output.Write([]byte(rs))
+			uversePrint(m, arg0, true)
 		},
 	)
 	defNative("recover",
@@ -786,3 +766,38 @@ func copyListToRunes(dst []rune, tvs []TypedValue) {
 		dst[i] = tvs[i].GetInt32()
 	}
 }
+
+// uversePrint is used for the print and println functions.
+// println passes newline = true.
+// xv contains the variadic argument passed to the function.
+func uversePrint(m *Machine, xv PointerValue, newline bool) {
+	xvl := xv.TV.GetLength()
+	switch xvl {
+	case 0:
+		if newline {
+			m.Output.Write(bNewline)
+		}
+	case 1:
+		ev := xv.TV.GetPointerAtIndexInt(m.Store, 0).Deref()
+		res := ev.Sprint(m)
+		io.WriteString(m.Output, res)
+		if newline {
+			m.Output.Write(bNewline)
+		}
+	default:
+		var buf bytes.Buffer
+		for i := 0; i < xvl; i++ {
+			if i != 0 { // Not the last item.
+				buf.WriteByte(' ')
+			}
+			ev := xv.TV.GetPointerAtIndexInt(m.Store, i).Deref()
+			buf.WriteString(ev.Sprint(m))
+		}
+		if newline {
+			buf.WriteByte('\n')
+		}
+		m.Output.Write(buf.Bytes())
+	}
+}
+
+var bNewline = []byte("\n")

gnovm/pkg/gnolang/uverse_test.go

@@ -1,7 +1,15 @@
 package gnolang
 
 import (
+	"bytes"
 	"testing"
+
+	"github.com/gnolang/gno/gnovm"
+	"github.com/gnolang/gno/tm2/pkg/db/memdb"
+	"github.com/gnolang/gno/tm2/pkg/store/dbadapter"
+	"github.com/gnolang/gno/tm2/pkg/store/iavl"
+	stypes "github.com/gnolang/gno/tm2/pkg/store/types"
+	"github.com/stretchr/testify/assert"
 )
 
 type uverseTestCases struct {
@@ -158,3 +166,135 @@ func TestIssue1337PrintNilSliceAsUndefined(t *testing.T) {
 		})
 	}
 }
+
+var pSink any = nil
+
+func BenchmarkGnoPrintln(b *testing.B) {
+	var buf bytes.Buffer
+	db := memdb.NewMemDB()
+	baseStore := dbadapter.StoreConstructor(db, stypes.StoreOptions{})
+	iavlStore := iavl.StoreConstructor(db, stypes.StoreOptions{})
+	store := NewStore(nil, baseStore, iavlStore)
+
+	m := NewMachineWithOptions(MachineOptions{
+		Output: &buf,
+		Store:  store,
+	})
+
+	program := `package p
+				func main() {
+					for i := 0; i < 1000; i++ {
+						println("abcdeffffffffffffffff1222 11111   11111")
+					}
+				}`
+	m.RunMemPackage(&gnovm.MemPackage{
+		Name: "p",
+		Path: "p",
+		Files: []*gnovm.MemFile{
+			{Name: "a.gno", Body: program},
+		},
+	}, false)
+
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		m.RunStatement(S(Call(Nx("main"))))
+		pSink = buf.String()
+	}
+
+	if pSink == nil {
+		b.Fatal("Benchmark did not run!")
+	}
+	pSink = nil
+}
+
+func TestGnoPrintAndPrintln(t *testing.T) {
+	tests := []struct {
+		name    string
+		srcArgs string
+		want    string
+	}{
+		{
+			"print with no args",
+			"print()",
+			"",
+		},
+		{
+			"print with 1 arg",
+			`print("1")`,
+			"1",
+		},
+		{
+			"print with 2 args",
+			`print("1", 2)`,
+			"1 2",
+		},
+		{
+			"print with 3 args",
+			`print("1", 2, "*")`,
+			"1 2 *",
+		},
+		{
+			"print with own spaces",
+			`print("1 ", 2, "*")`,
+			"1  2 *",
+		},
+		{
+			"println with no args",
+			"println()",
+			"\n",
+		},
+		{
+			"print with 1 arg",
+			`println("1")`,
+			"1\n",
+		},
+		{
+			"println with 2 args",
+			`println("1", 2)`,
+			"1 2\n",
+		},
+		{
+			"println with 3 args",
+			`println("1", 2, "*")`,
+			"1 2 *\n",
+		},
+		{
+			"println with own spaces",
+			`println("1 ", 2, "*")`,
+			"1  2 *\n",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var buf bytes.Buffer
+			db := memdb.NewMemDB()
+			baseStore := dbadapter.StoreConstructor(db, stypes.StoreOptions{})
+			iavlStore := iavl.StoreConstructor(db, stypes.StoreOptions{})
+			store := NewStore(nil, baseStore, iavlStore)
+
+			m := NewMachineWithOptions(MachineOptions{
+				Output: &buf,
+				Store:  store,
+			})
+
+			program := `package p
+				func main() {` + tt.srcArgs + "\n}"
+			m.RunMemPackage(&gnovm.MemPackage{
+				Name: "p",
+				Path: "p",
+				Files: []*gnovm.MemFile{
+					{Name: "a.gno", Body: program},
+				},
+			}, false)
+
+			buf.Reset()
+			m.RunStatement(S(Call(Nx("main"))))
+			got := buf.String()
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}

go.mod

@@ -14,7 +14,6 @@ require (
 	github.com/davecgh/go-spew v1.1.1
 	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.3.0
 	github.com/fortytw2/leaktest v1.3.0
-	github.com/google/go-cmp v0.6.0
 	github.com/google/gofuzz v1.2.0
 	github.com/gorilla/websocket v1.5.3
 	github.com/libp2p/go-buffer-pool v0.1.0

tm2/pkg/bft/rpc/lib/server/write_endpoints_test.go

@@ -6,7 +6,6 @@ import (
 	"net/http/httptest"
 	"testing"
 
-	"github.com/google/go-cmp/cmp"
 	"github.com/stretchr/testify/assert"
 
 	types "github.com/gnolang/gno/tm2/pkg/bft/rpc/lib/types"
@@ -27,7 +26,5 @@ func TestWriteListOfEndpoints(t *testing.T) {
 	assert.NoError(t, err)
 	gotResp := string(blob)
 	wantResp := `<html><body><br>Available endpoints:<br><a href="//localhost/d">//localhost/d</a></br><br>Endpoints that require arguments:<br><a href="//localhost/c?s=_&i=_">//localhost/c?s=_&i=_</a></br></body></html>`
-	if diff := cmp.Diff(gotResp, wantResp); diff != "" {
-		t.Fatalf("Mismatch response: got - want +\n%s", diff)
-	}
+	assert.Equal(t, wantResp, gotResp)
 }

tm2/pkg/sdk/auth/params_test.go

@@ -4,7 +4,7 @@ import (
 	"reflect"
 	"testing"
 
-	"github.com/google/go-cmp/cmp"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -123,9 +123,7 @@ func TestParamsString(t *testing.T) {
 	for _, tt := range cases {
 		t.Run(tt.name, func(t *testing.T) {
 			got := tt.params.String()
-			if diff := cmp.Diff(got, tt.want); diff != "" {
-				t.Fatalf("Mismatch: got - want +\n%s", diff)
-			}
+			assert.Equal(t, tt.want, got)
 		})
 	}
 }