Ehhhhhhh I thought it was a bit of a mishmash, at least before ryujit?
i.e. I think the x64 framework compiler was based on MSVC, but the x86 was a bit of a different beast. That was part of why they did RyuJit in the first place, to help unify the JITs between the large divergence in how they worked [0].
One big thing being, AFAIK the old 32 bit JIT would never use SSE2 outside of some block copy type stuff. They assumed a safe baseline for most other instructions and stuck with that (although, there can be good reasons for this, e.x. consistency with x87 behavior.)
Will also add that the old x64 compiler sometimes really did do some questionable stuff, i.e. when we flipped things to use it we never really saw a perf benefit even when dealing with larger datatypes/etc that should have seen a benefit from wider registers.
RyuJit definitely has fixed that, but... again, the past is a bit hazy.
[0] - https://devblogs.microsoft.com/dotnet/ryujit-the-next-genera...
i.e. I think the x64 framework compiler was based on MSVC, but the x86 was a bit of a different beast. That was part of why they did RyuJit in the first place, to help unify the JITs between the large divergence in how they worked [0].
One big thing being, AFAIK the old 32 bit JIT would never use SSE2 outside of some block copy type stuff. They assumed a safe baseline for most other instructions and stuck with that (although, there can be good reasons for this, e.x. consistency with x87 behavior.)
Will also add that the old x64 compiler sometimes really did do some questionable stuff, i.e. when we flipped things to use it we never really saw a perf benefit even when dealing with larger datatypes/etc that should have seen a benefit from wider registers.
RyuJit definitely has fixed that, but... again, the past is a bit hazy.
[0] - https://devblogs.microsoft.com/dotnet/ryujit-the-next-genera...