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JIT should be able to elide zeroing of fields after allocations #96942
Description
using System;
class Program
{
static void Main()
{
Program p = new();
p.Test = false;
}
public bool Test;
}Codegen:
call CORINFO_HELP_NEWSFAST
mov byte ptr [rax+0x08], 0Expected:
call CORINFO_HELP_NEWSFASTI looked at representing this in VN once, but it seemed hard with how we represent memory in VN.
Activity
EgorBo commentedon Jan 13, 2024
... and remove the allocation after it 🙂
jakobbotsch commentedon May 28, 2025
I am not totally convinced this is a good idea anymore since removing explicit stores can break store-to-load forwarding done by the CPU, which comes with a large penalty. I will move this to future as something to potentially investigate.
EgorBo commentedon May 28, 2025
It's cool that your initial snippet is now optimized to just
no-opwith help of EA 🙂 I know it's not what the issue is about, but still..