[PATCH] D73000: [InstCombine] Optimize strchr(cststr, C)

[Hans Wennborg via Phabricator via llvm-commits]

hans added inline comments.


================
Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:948
     // target.
-    // FIXME: On a 64 bit architecture this prevents us from using the
-    // interesting range of alpha ascii chars. We could do better by emitting
-    // two bitfields or shifting the range by 64 if no lower chars are used.
-    if (!DL.fitsInLegalInteger(Max + 1))
-      return nullptr;
+    if (!DL.fitsInLegalInteger(Max + 1)) {
+      // Build chain of OR comparisons
----------------
xbolva00 wrote:
> joerg wrote:
> > The switch table logic is fine with lowering it to a multiple tests, isn't it?
> Hmm.. building switch directly is for some cases* better choice** than ORs, but I am wondering if this is best solution here -  Maybe @hans could give us some recommendations here?
> 
> * https://godbolt.org/z/BuR6St (switch is faster than ors).
> ** Ideally, we should turn chain of ORs to switch too.
> 
> Ideas?
> 
> 
I think we (SimplifyCFG) does turn a chain of ORs into a switch, but only logical or, not bitwise. Maybe emitting  a chain of logical or would be good here?


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  https://reviews.llvm.org/D73000/new/

https://reviews.llvm.org/D73000