From bf1ae5e254f8f6f6f3dfe9438d14bef9b955f01f Mon Sep 17 00:00:00 2001 From: Dale Johannesen Date: Tue, 20 Jul 2010 00:50:13 +0000 Subject: [PATCH] Don't hoist things out of a large switch inside a loop, for the reasons in the comments. This is a major win on 253.perlbmk on ARM Darwin. I expect it to be a good heuristic in general, but it's possible some things will regress; I'll be watching. 7940152. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108792 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/MachineLICM.cpp | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/lib/CodeGen/MachineLICM.cpp b/lib/CodeGen/MachineLICM.cpp index 4c054f51f3a..83f66ce0948 100644 --- a/lib/CodeGen/MachineLICM.cpp +++ b/lib/CodeGen/MachineLICM.cpp @@ -489,8 +489,12 @@ void MachineLICM::HoistRegion(MachineDomTreeNode *N) { } const std::vector &Children = N->getChildren(); - for (unsigned I = 0, E = Children.size(); I != E; ++I) - HoistRegion(Children[I]); + // Don't hoist things out of a large switch statement. This often causes + // code to be hoisted that wasn't going to be executed, and increases + // register pressure in a situation where it's likely to matter. + if (Children.size() < 10) + for (unsigned I = 0, E = Children.size(); I != E; ++I) + HoistRegion(Children[I]); } /// IsLICMCandidate - Returns true if the instruction may be a suitable