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Don't hoist things out of a large switch inside a

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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
This commit is contained in:
Dale Johannesen 2010-07-20 00:50:13 +00:00
parent 7a2b701ef6
commit bf1ae5e254
1 changed files with 6 additions and 2 deletions
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8
lib/CodeGen/MachineLICM.cpp
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@ -489,8 +489,12 @@ void MachineLICM::HoistRegion(MachineDomTreeNode *N) {
}
const std::vector<MachineDomTreeNode*> &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