[Torque] Do Witness Rechecks() at loop starts

Since these Recheck() calls are usually combined with a bailout,
doing them at the end of loops means we have to increment one or
more bailout variables, which is hard to understand.

Change-Id: I595ea592f31762da5abd85bfa7556eb39e3c9430
Reviewed-on: https://chromium-review.googlesource.com/c/1478694
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59727}

src/builtins/array-every.tq

@@ -92,6 +92,8 @@ namespace array {
 
     // Build a fast loop over the smi array.
     for (; k < len; k++) {
+      fastO.Recheck() otherwise goto Bailout(k);
+
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastO.Get().length) goto Bailout(k);
 
@@ -105,7 +107,6 @@ namespace array {
         }
       }
       label FoundHole {}
-      fastO.Recheck() otherwise goto Bailout(k + 1);
     }
     return True;
   }

src/builtins/array-filter.tq

@@ -107,6 +107,8 @@ namespace array_filter {
 
     // Build a fast loop over the smi array.
     for (; k < len; k++) {
+      fastO.Recheck() otherwise goto Bailout(k, to);
+
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastO.Get().length) goto Bailout(k, to);
       const value: Object = LoadElementNoHole<FixedArrayType>(fastO.Get(), k)
@@ -128,7 +130,6 @@ namespace array_filter {
         }
         to = to + 1;
       }
-      fastO.Recheck() otherwise goto Bailout(k + 1, to);
     }
   }
 

src/builtins/array-foreach.tq

@@ -77,12 +77,13 @@ namespace array_foreach {
 
     // Build a fast loop over the smi array.
     for (; k < len; k++) {
+      fastO.Recheck() otherwise goto Bailout(k);
+
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastO.Get().length) goto Bailout(k);
       const value: Object = LoadElementNoHole<FixedArrayType>(fastO.Get(), k)
           otherwise continue;
       Call(context, callbackfn, thisArg, value, k, fastO.Get());
-      fastO.Recheck() otherwise goto Bailout(k + 1);
     }
   }
 

src/builtins/array-map.tq

@@ -191,6 +191,8 @@ namespace array_map {
     // Build a fast loop over the smi array.
     // 7. Repeat, while k < len.
     for (; k < len; k++) {
+      fastO.Recheck() otherwise goto Bailout(v, k);
+
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastO.Get().length) goto Bailout(v, k);
 
@@ -200,7 +202,6 @@ namespace array_map {
         const result: Object =
             Call(context, callbackfn, thisArg, value, k, fastO.Get());
         v.StoreResult(k, result);
-        fastO.Recheck() otherwise goto Bailout(v, k + 1);
       }
       label FoundHole {
         // Our output array must necessarily be holey because of holes in

src/builtins/array-some.tq

@@ -92,6 +92,8 @@ namespace array {
 
     // Build a fast loop over the smi array.
     for (; k < len; k++) {
+      fastO.Recheck() otherwise goto Bailout(k);
+
       // Ensure that we haven't walked beyond a possibly updated length.
       if (k >= fastO.Get().length) goto Bailout(k);
 
@@ -105,7 +107,6 @@ namespace array {
         }
       }
       label FoundHole {}
-      fastO.Recheck() otherwise goto Bailout(k + 1);
     }
     return False;
   }