From f9043c84a7afee524650fca9c93d9940fc9f4d8c Mon Sep 17 00:00:00 2001
From: Delyan Angelov <delian66@gmail.com>
Date: Thu, 22 Dec 2022 20:08:05 +0200
Subject: [PATCH] builtin: optimise the initialisation of the common 1 byte
 element arrays `[]u8`

---
 vlib/builtin/array.v               | 53 +++++++++++++++++++-----------
 vlib/builtin/array_d_gcboehm_opt.v | 16 +++++++--
 2 files changed, 47 insertions(+), 22 deletions(-)

diff --git a/vlib/builtin/array.v b/vlib/builtin/array.v
index 7d9deb2c58..9a006aaecf 100644
--- a/vlib/builtin/array.v
+++ b/vlib/builtin/array.v
@@ -56,9 +56,18 @@ fn __new_array_with_default(mylen int, cap int, elm_size int, val voidptr) array
 	if val != 0 {
 		mut eptr := &u8(arr.data)
 		unsafe {
-			for _ in 0 .. arr.len {
-				vmemcpy(eptr, val, arr.element_size)
-				eptr += arr.element_size
+			if eptr != nil {
+				if arr.element_size == 1 {
+					byte_value := *(&u8(val))
+					for i in 0 .. arr.len {
+						eptr[i] = byte_value
+					}
+				} else {
+					for _ in 0 .. arr.len {
+						vmemcpy(eptr, val, arr.element_size)
+						eptr += arr.element_size
+					}
+				}
 			}
 		}
 	}
@@ -75,10 +84,12 @@ fn __new_array_with_array_default(mylen int, cap int, elm_size int, val array, d
 	}
 	mut eptr := &u8(arr.data)
 	unsafe {
-		for _ in 0 .. arr.len {
-			val_clone := val.clone_to_depth(depth)
-			vmemcpy(eptr, &val_clone, arr.element_size)
-			eptr += arr.element_size
+		if eptr != nil {
+			for _ in 0 .. arr.len {
+				val_clone := val.clone_to_depth(depth)
+				vmemcpy(eptr, &val_clone, arr.element_size)
+				eptr += arr.element_size
+			}
 		}
 	}
 	return arr
@@ -94,10 +105,12 @@ fn __new_array_with_map_default(mylen int, cap int, elm_size int, val map) array
 	}
 	mut eptr := &u8(arr.data)
 	unsafe {
-		for _ in 0 .. arr.len {
-			val_clone := val.clone()
-			vmemcpy(eptr, &val_clone, arr.element_size)
-			eptr += arr.element_size
+		if eptr != nil {
+			for _ in 0 .. arr.len {
+				val_clone := val.clone()
+				vmemcpy(eptr, &val_clone, arr.element_size)
+				eptr += arr.element_size
+			}
 		}
 	}
 	return arr
@@ -191,14 +204,16 @@ pub fn (a array) repeat_to_depth(count int, depth int) array {
 		arr_step_size := u64(a.len) * u64(arr.element_size)
 		mut eptr := &u8(arr.data)
 		unsafe {
-			for _ in 0 .. count {
-				if depth > 0 {
-					ary_clone := a.clone_to_depth(depth)
-					vmemcpy(eptr, &u8(ary_clone.data), a_total_size)
-				} else {
-					vmemcpy(eptr, &u8(a.data), a_total_size)
+			if eptr != nil {
+				for _ in 0 .. count {
+					if depth > 0 {
+						ary_clone := a.clone_to_depth(depth)
+						vmemcpy(eptr, &u8(ary_clone.data), a_total_size)
+					} else {
+						vmemcpy(eptr, &u8(a.data), a_total_size)
+					}
+					eptr += arr_step_size
 				}
-				eptr += arr_step_size
 			}
 		}
 	}
@@ -661,7 +676,7 @@ pub fn (mut a3 array) push_many(val voidptr, size int) {
 
 // reverse_in_place reverses existing array data, modifying original array.
 pub fn (mut a array) reverse_in_place() {
-	if a.len < 2 {
+	if a.len < 2 || a.element_size == 0 {
 		return
 	}
 	unsafe {
diff --git a/vlib/builtin/array_d_gcboehm_opt.v b/vlib/builtin/array_d_gcboehm_opt.v
index 6522fa269f..70f24ab7ba 100644
--- a/vlib/builtin/array_d_gcboehm_opt.v
+++ b/vlib/builtin/array_d_gcboehm_opt.v
@@ -24,9 +24,19 @@ fn __new_array_with_default_noscan(mylen int, cap int, elm_size int, val voidptr
 		len: mylen
 		cap: cap_
 	}
-	if val != 0 {
-		for i in 0 .. arr.len {
-			unsafe { arr.set_unsafe(i, val) }
+	if val != 0 && arr.data != unsafe { nil } {
+		if elm_size == 1 {
+			byte_value := *(&u8(val))
+			dptr := &u8(arr.data)
+			for i in 0 .. arr.len {
+				unsafe {
+					dptr[i] = byte_value
+				}
+			}
+		} else {
+			for i in 0 .. arr.len {
+				unsafe { arr.set_unsafe(i, val) }
+			}
 		}
 	}
 	return arr