[PATCH] D150994: Bump coalescing limit

[Matthias Braun via Phabricator via llvm-commits]

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This bumps the "large-interval-freq-threshold" limit in the register coalescer to 256. The limit was introduced in https://reviews.llvm.org/D59143 without much justify for the particular value "100", so I hope bumping it is ok.

This change is motivated by bad codegen for the popular crc32c algorithm; the code is often based/copied from this implementation: https://github.com/htot/crc32c/blob/master/crc32c/crc32intelc.cc which uses a duffs-device pattern with 128 switch-cases. It can be other projects such as rocksdb (https://github.com/facebook/rocksdb/blob/main/util/crc32c.cc) and folly (https://github.com/facebook/folly/blob/main/folly/hash/detail/Crc32cDetail.cpp) which are important use cases for us.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D150994

Files:
  llvm/lib/CodeGen/RegisterCoalescer.cpp


Index: llvm/lib/CodeGen/RegisterCoalescer.cpp
===================================================================
--- llvm/lib/CodeGen/RegisterCoalescer.cpp
+++ llvm/lib/CodeGen/RegisterCoalescer.cpp
@@ -116,7 +116,7 @@
     cl::desc("For a large interval, if it is coalesed with other live "
              "intervals many times more than the threshold, stop its "
              "coalescing to control the compile time. "),
-    cl::init(100));
+    cl::init(256));
 
 namespace {
 


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