[llvm] [AArch64] Change IssueWidth to 6 in AArch64SchedNeoverseV2.td (PR #142565)

[Sjoerd Meijer via llvm-commits]

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@@ -14,7 +14,7 @@
 //===----------------------------------------------------------------------===//
 
 def NeoverseV2Model : SchedMachineModel {
-  let IssueWidth            =  16; // Micro-ops dispatched at a time.
+  let IssueWidth            =   6; // Micro-ops dispatched at a time.
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sjoerdmeijer wrote:

Nit: can we update the comment, and try to be more specific what we mean here, because things are all a bit vague in the SWOG and here too. So a bit more rationale that we are now more modelling the dispatch constraints rather than the issue width, and that 6 is better than 8 because that's what benchmarks shows. 
If we get it right here, we might get it right elsewhere too, because these things tend to be copied from one scheduling file to the next one. ;-) 

https://github.com/llvm/llvm-project/pull/142565