Andrei Alexandrescu needs to read this

rikki cattermole rikki at
Sun Oct 27 23:04:52 UTC 2019

On 28/10/2019 9:11 AM, Mark wrote:
> On Wednesday, 23 October 2019 at 23:51:16 UTC, H. S. Teoh wrote:
>> Another recent development is the occasional divergence of performance 
>> characteristics of CPUs across members of the same family, i.e., the 
>> same instruction on two different CPU models may perform quite 
>> differently.  Meaning that this sort of low-level optimization is 
>> really best left to the optimizer to optimize for the actual target 
>> CPU, rather than to choose a fixed series of instructions in an asm 
>> block that may perform poorly on some CPUs.  (This is also where JIT 
>> compilation can win over static compilation, if you ship a generic 
>> binary that isn't specifically targeted for the customer's CPU model.)
>> T
> Would it be reasonable to say that modern CPUs basically do JIT 
> compilation of assembly instructions? Or at the very least, that they 
> have a built-in "runtime" that is responsible for all that ILP magic - 
> cache policy algorithms, MESI protocol, the branch predictor and so on. 
> If so, you could argue that the Itanium was an attempt to avoid this 
> "runtime" and transfer all these responsibilities to the compiler and/or 
> programmer. Not a very successful one, apparently.
> It is also a bit analogous to the GC vs. deterministic manual memory 
> management debate.

I have described modern x86 cpu's as an application VM, so I will agree 
with you :)

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