perf(gnovm/pkg/gnolang): make ReadMemPackageFromList singly use byteslices from os.ReadFile

gnovm/pkg/gnolang/bench_test.go

@@ -1,6 +1,8 @@
 package gnolang
 
 import (
+	"path/filepath"
+	"runtime"
 	"testing"
 )
 
@@ -29,3 +31,25 @@ func BenchmarkPkgIDFromPkgPath(b *testing.B) {
 	}
 	sink = nil
 }
+
+func BenchmarkReadMemPackage(b *testing.B) {
+	_, currentFile, _, ok := runtime.Caller(0)
+	_ = ok // Appease golang-ci
+	rootOfRepo, err := filepath.Abs(filepath.Join(filepath.Dir(currentFile), "..", "..", ".."))
+	if err != nil {
+		b.Fatal(err)
+	}
+	demoDir := filepath.Join(rootOfRepo, "examples", "gno.land", "p", "demo")
+	ufmtDir := filepath.Join(demoDir, "ufmt")
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		sink = MustReadMemPackage(ufmtDir, "ufmt")
+	}
+
+	if sink == nil {
+		b.Fatal("Benchmark did not run!")
+	}
+	sink = nil
+}

gnovm/pkg/gnolang/nodes.go

@@ -11,6 +11,7 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"unsafe"
 
 	"github.com/gnolang/gno/gnovm"
 	"go.uber.org/multierr"
@@ -1317,7 +1318,10 @@ func ReadMemPackageFromList(list []string, pkgPath string) (*gnovm.MemPackage, e
 		}
 		// XXX: should check that all pkg names are the same (else package is invalid)
 		if pkgName == "" && strings.HasSuffix(fname, ".gno") {
-			pkgName, err = PackageNameFromFileBody(fname, string(bz))
+			// The string derived from bz is never modified inside PackageNameFromFileBody
+			// hence shave these unnecessary allocations by an unsafe
+			// byteslice->string conversion per https://github.com/gnolang/gno/issues/3598
+			pkgName, err = PackageNameFromFileBody(fname, unsafeBytesliceToStr(bz))
 			if err != nil {
 				return nil, err
 			}
@@ -1328,7 +1332,12 @@ func ReadMemPackageFromList(list []string, pkgPath string) (*gnovm.MemPackage, e
 		memPkg.Files = append(memPkg.Files,
 			&gnovm.MemFile{
 				Name: fname,
-				Body: string(bz),
+				// The string derived from bz is never modified, hence to shave
+				// unnecessary allocations, perform this unsafe byteslice->string
+				// conversion per https://github.com/gnolang/gno/issues/3598
+				// and the Go garbage collector will knows to garbage collect
+				// bz when no other object points to that memory.
+				Body: unsafeBytesliceToStr(bz),
 			})
 	}
 
@@ -1343,6 +1352,13 @@ func ReadMemPackageFromList(list []string, pkgPath string) (*gnovm.MemPackage, e
 	return memPkg, nil
 }
 
+// unsafeBytesliceToStr helps rid the unnecessary byteslice->string conversion
+// in instances where we definitely would not be modifying the input byteslice
+// such as in ReadMemPackageFromList.
+func unsafeBytesliceToStr(bz []byte) string {
+	return unsafe.String(&bz[0], len(bz))
+}
+
 // MustReadMemPackageFromList is a wrapper around [ReadMemPackageFromList] that panics on error.
 func MustReadMemPackageFromList(list []string, pkgPath string) *gnovm.MemPackage {
 	pkg, err := ReadMemPackageFromList(list, pkgPath)