[PATCH] D100691: [TableGen] Store predicates in PatternToMatch as ListInit *. Add string for HwModeFeatures

[Paul C. Anagnostopoulos via Phabricator via llvm-commits]

Paul-C-Anagnostopoulos added inline comments.


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Comment at: llvm/utils/TableGen/CodeGenDAGPatterns.cpp:1477
+    PredicateCheck += HwModeFeatures;
+    PredicateCheck += "\"))";
   }
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craig.topper wrote:
> Paul-C-Anagnostopoulos wrote:
> > Any reason you didn't combine the catenations with '+' ?
> Concatenating them would produce a temporary std::string that would need a heap allocation. That would then need to be copied into the SmallString. If the total string is small enough the SmallString won't heap allocate. If we copy each piece in separately we avoid heap allocations for temporaries.
Sounds like there's room for an optimization that looks at the complete sequence of catenations to decide whether there is room in the SmallString. But good to know.


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  https://reviews.llvm.org/D100691/new/

https://reviews.llvm.org/D100691