dotnet/runtime
GitHub で見るCSE seems to fail when writing `x / cns` and `x % cns` for unsigned integers
Open
#119,131 opened on 2025年8月27日
area-CodeGen-coreclrhelp wantedtenet-performance
Repository metrics
- Stars
- (17,886 stars)
- PR merge metrics
- (平均マージ 12d 11h) (30d で 661 merged PRs)
説明
Description
CSE seems to fail if I write something like:
uint Natural(uint index)
{
uint arrIndex = index / 3;
uint bitIndex = index % 3;
return arrIndex + bitIndex;
}
(it does the division twice).
This seems to only be an issue for unsigned integers not using DivRem.
Configuration
Seems to reproduce on any .NET version on godbolt - I've only checked the issue on x64.
Regression?
Probably not.
Analysis
@tannergooding was saying it seems that UMOD might be missing early expansion altogether & it's getting carried down to rationalisation.