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Put a heuristic in place to prevent GVN from falling into bad cases with massively complicated CFGs.

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This speeds up a particular testcase from 12+ hours to 5 seconds with little perceptible loss of quality.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55391 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2008-08-26 22:07:42 +00:00
parent 3200d92947
commit 516eb1c139
1 changed files with 6 additions and 0 deletions
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6
lib/Transforms/Scalar/GVN.cpp
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@ -862,6 +862,12 @@ bool GVN::processNonLocalLoad(LoadInst* L,
DenseMap<BasicBlock*, Value*> deps;
MD.getNonLocalDependency(L, deps);
// If we had to process more than one hundred blocks to find the
// dependencies, this load isn't worth worrying about. Optimizing
// it will be too expensive.
if (deps.size() > 100)
return false;
DenseMap<BasicBlock*, Value*> repl;
// Filter out useless results (non-locals, etc)