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By default, use Early-CSE instead of GVN for vectorization cleanup.

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As has been suggested by Duncan and others, Early-CSE and GVN should
do similar redundancy elimination, but Early-CSE is much less expensive.
Most of my autovectorization benchmarks show a performance regresion, but
all of these are < 0.1%, and so I think that it is still worth using
the less expensive pass.

llvm-svn: 154673
This commit is contained in:
Hal Finkel 2012-04-13 17:15:33 +00:00
parent 53db93eead
commit f8611de2a6
1 changed files with 9 additions and 2 deletions
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11
lib/Transforms/IPO/PassManagerBuilder.cpp
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@ -35,6 +35,11 @@ using namespace llvm;
static cl::opt<bool>
RunVectorization("vectorize", cl::desc("Run vectorization passes"));
static cl::opt<bool>
UseGVNAfterVectorization("use-gvn-after-vectorization",
cl::init(false), cl::Hidden,
cl::desc("Run GVN instead of Early CSE after vectorization passes"));
PassManagerBuilder::PassManagerBuilder() {
OptLevel = 2;
SizeLevel = 0;
@ -182,8 +187,10 @@ void PassManagerBuilder::populateModulePassManager(PassManagerBase &MPM) {
if (Vectorize) {
MPM.add(createBBVectorizePass());
MPM.add(createInstructionCombiningPass());
if (OptLevel > 1)
MPM.add(createGVNPass()); // Remove redundancies
if (OptLevel > 1 && UseGVNAfterVectorization)
MPM.add(createGVNPass()); // Remove redundancies
else
MPM.add(createEarlyCSEPass()); // Catch trivial redundancies
}
MPM.add(createAggressiveDCEPass()); // Delete dead instructions