Andrei Alexandrescu needs to read this

drug drug2004 at
Sun Oct 27 20:39:45 UTC 2019

27.10.2019 23:11, Mark пишет:
> 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.
Wasn't Itanium fail be caused that AMD suggested another architecture 
that was capable to run existing software while in case of Itanium users 
was forced to recompile their source code? So Itanium failed just 
because it was incompatible to x86?

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