Add fast paths for array's fill method (#2307)

Author: MaxGraey

Diff for: std/assembly/array.ts

@@ -173,6 +173,34 @@ export class Array<T> {
         );
       }
     } else {
+      if (ASC_SHRINK_LEVEL <= 1) {
+        if (isInteger<T>()) {
+          // @ts-ignore
+          if (value == <T>0 | value == <T>-1) {
+            if (start < end) {
+              memory.fill(
+                ptr + (<usize>start << alignof<T>()),
+                u8(value),
+                <usize>(end - start) << alignof<T>()
+              );
+            }
+            return this;
+          }
+        } else if (isFloat<T>()) {
+          // for floating non-negative zeros we can use fast memory.fill
+          if ((sizeof<T>() == 4 && reinterpret<u32>(f32(value)) == 0) ||
+              (sizeof<T>() == 8 && reinterpret<u64>(f64(value)) == 0)) {
+            if (start < end) {
+              memory.fill(
+                ptr + (<usize>start << alignof<T>()),
+                0,
+                <usize>(end - start) << alignof<T>()
+              );
+            }
+            return this;
+          }
+        }
+      }
       for (; start < end; ++start) {
         store<T>(ptr + (<usize>start << alignof<T>()), value);
       }

Diff for: std/assembly/staticarray.ts

@@ -160,6 +160,34 @@ export class StaticArray<T> {
         );
       }
     } else {
+      if (ASC_SHRINK_LEVEL <= 1) {
+        if (isInteger<T>()) {
+          // @ts-ignore
+          if (value == <T>0 | value == <T>-1) {
+            if (start < end) {
+              memory.fill(
+                ptr + (<usize>start << alignof<T>()),
+                u8(value),
+                <usize>(end - start) << alignof<T>()
+              );
+            }
+            return this;
+          }
+        } else if (isFloat<T>()) {
+          // for floating non-negative zeros we can use fast memory.fill
+          if ((sizeof<T>() == 4 && reinterpret<u32>(f32(value)) == 0) ||
+              (sizeof<T>() == 8 && reinterpret<u64>(f64(value)) == 0)) {
+            if (start < end) {
+              memory.fill(
+                ptr + (<usize>start << alignof<T>()),
+                0,
+                <usize>(end - start) << alignof<T>()
+              );
+            }
+            return this;
+          }
+        }
+      }
       for (; start < end; ++start) {
         store<T>(ptr + (<usize>start << alignof<T>()), value);
       }

Diff for: std/assembly/typedarray.ts

@@ -1571,6 +1571,34 @@ function FILL<TArray extends ArrayBufferView, T extends number>(
   if (sizeof<T>() == 1) {
     if (start < end) memory.fill(ptr + <usize>start, <u8>value, <usize>(end - start));
   } else {
+    if (ASC_SHRINK_LEVEL <= 1) {
+      if (isInteger<T>()) {
+        // @ts-ignore
+        if (value == <T>0 | value == <T>-1) {
+          if (start < end) {
+            memory.fill(
+              ptr + (<usize>start << alignof<T>()),
+              u8(value),
+              <usize>(end - start) << alignof<T>()
+            );
+          }
+          return array;
+        }
+      } else if (isFloat<T>()) {
+        // for floating non-negative zeros we can use fast memory.fill
+        if ((sizeof<T>() == 4 && reinterpret<u32>(f32(value)) == 0) ||
+            (sizeof<T>() == 8 && reinterpret<u64>(f64(value)) == 0)) {
+          if (start < end) {
+            memory.fill(
+              ptr + (<usize>start << alignof<T>()),
+              0,
+              <usize>(end - start) << alignof<T>()
+            );
+          }
+          return array;
+        }
+      }
+    }
     for (; start < end; ++start) {
       store<T>(ptr + (<usize>start << alignof<T>()), value);
     }

Diff for: tests/compiler/std-wasi/crypto.debug.wat

@@ -4920,7 +4920,7 @@
   if
    i32.const 448
    i32.const 656
-   i32.const 1870
+   i32.const 1898
    i32.const 5
    call $~lib/wasi/index/abort
    unreachable
@@ -4939,7 +4939,7 @@
     if
      i32.const 144
      i32.const 656
-     i32.const 1875
+     i32.const 1903
      i32.const 9
      call $~lib/wasi/index/abort
      unreachable
@@ -4951,7 +4951,7 @@
    else
     i32.const 144
     i32.const 656
-    i32.const 1879
+    i32.const 1907
     i32.const 7
     call $~lib/wasi/index/abort
     unreachable
@@ -4969,7 +4969,7 @@
    if
     i32.const 144
     i32.const 656
-    i32.const 1884
+    i32.const 1912
     i32.const 7
     call $~lib/wasi/index/abort
     unreachable

Diff for: tests/compiler/std-wasi/crypto.release.wat

@@ -3717,7 +3717,7 @@
   if
    i32.const 1472
    i32.const 1680
-   i32.const 1870
+   i32.const 1898
    i32.const 5
    call $~lib/wasi/index/abort
    unreachable
@@ -3736,7 +3736,7 @@
    else
     i32.const 1168
     i32.const 1680
-    i32.const 1879
+    i32.const 1907
     i32.const 7
     call $~lib/wasi/index/abort
     unreachable
@@ -3751,7 +3751,7 @@
    if
     i32.const 1168
     i32.const 1680
-    i32.const 1884
+    i32.const 1912
     i32.const 7
     call $~lib/wasi/index/abort
     unreachable