JIT: Block clonning for subsequent bounds checks #112524
Description
If we have:
void Test(int[] arr, int i)
{
arr[i + 0] = 0;
arr[i + 1] = 0;
arr[i + 2] = 0;
arr[i + 3] = 0;
}Which generates a single BasicBlock with either multiple statements or a single statement with multiple COMMAs containing STOREIND node, we should be able to just clone it and remove all bound checks in the fast path:
public void Test(int[] arr, int i)
{
if (i >= 0 && i < arr.Length - 3)
{
// Fast path: no bounds checks
arr[i + 0] = 0;
arr[i + 1] = 0;
arr[i + 2] = 0;
arr[i + 3] = 0;
}
else
{
// Slow fallback
arr[i + 0] = 0;
arr[i + 1] = 0;
arr[i + 2] = 0;
arr[i + 3] = 0;
}
}So, essentially, a loop clonning but for non-loop stuff.
cc @dotnet/jit-contrib opinions? such patterns aren't uncommon in BCL