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author | Chris Lattner <sabre@nondot.org> | 2003-06-28 21:54:55 +0000 |
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committer | Chris Lattner <sabre@nondot.org> | 2003-06-28 21:54:55 +0000 |
commit | 934fe856b58de326c9bca98b1493745d1c99727d (patch) | |
tree | e290f9e4d940ca7cf1f890035836e70c0b02ce40 | |
parent | 34e0ada19af7810934ba3a5f831a7b77a73ff62c (diff) | |
download | external_llvm-934fe856b58de326c9bca98b1493745d1c99727d.zip external_llvm-934fe856b58de326c9bca98b1493745d1c99727d.tar.gz external_llvm-934fe856b58de326c9bca98b1493745d1c99727d.tar.bz2 |
New pass to perform DSA based optimizations. Initially we just support turning
globals into constants if we can prove it's safe
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6941 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r-- | lib/Analysis/DataStructure/DataStructureOpt.cpp | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/lib/Analysis/DataStructure/DataStructureOpt.cpp b/lib/Analysis/DataStructure/DataStructureOpt.cpp new file mode 100644 index 0000000..ad5b894 --- /dev/null +++ b/lib/Analysis/DataStructure/DataStructureOpt.cpp @@ -0,0 +1,76 @@ +//===- DataStructureOpt.cpp - Data Structure Analysis Based Optimizations -===// +// +// This pass uses DSA to a series of simple optimizations, like marking +// unwritten global variables 'constant'. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Analysis/DataStructure.h" +#include "llvm/Analysis/DSGraph.h" +#include "llvm/Module.h" +#include "llvm/Constant.h" +#include "Support/Statistic.h" + +namespace { + Statistic<> + NumGlobalsConstanted("ds-opt", "Number of globals marked constant"); + + class DSOpt : public Pass { + TDDataStructures *TD; + public: + bool run(Module &M) { + TD = &getAnalysis<TDDataStructures>(); + bool Changed = OptimizeGlobals(M); + return Changed; + } + + virtual void getAnalysisUsage(AnalysisUsage &AU) const { + AU.addRequired<TDDataStructures>(); // Uses TD Datastructures + AU.addPreserved<LocalDataStructures>(); // Preserves local... + AU.addPreserved<TDDataStructures>(); // Preserves bu... + AU.addPreserved<BUDataStructures>(); // Preserves td... + } + + private: + bool OptimizeGlobals(Module &M); + }; + + RegisterOpt<DSOpt> X("ds-opt", "DSA-based simple optimizations"); +} + + +/// OptimizeGlobals - This method uses information taken from DSA to optimize +/// global variables. +/// +bool DSOpt::OptimizeGlobals(Module &M) { + DSGraph &GG = TD->getGlobalsGraph(); + const DSGraph::ScalarMapTy &SM = GG.getScalarMap(); + bool Changed = false; + + for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I) + if (!I->isExternal()) { // Loop over all of the non-external globals... + // Look up the node corresponding to this global, if it exists. + DSNode *GNode = 0; + DSGraph::ScalarMapTy::const_iterator SMI = SM.find(I); + if (SMI != SM.end()) GNode = SMI->second.getNode(); + + if (GNode == 0 && I->hasInternalLinkage()) { + // If there is no entry in the scalar map for this global, it was never + // referenced in the program. If it has internal linkage, that means we + // can delete it. We don't ACTUALLY want to delete the global, just + // remove anything that references the global: later passes will take + // care of nuking it. + I->replaceAllUsesWith(Constant::getNullValue((Type*)I->getType())); + } else if (GNode && GNode->isComplete()) { + // We expect that there will almost always be a node for this global. + // If there is, and the node doesn't have the M bit set, we can set the + // 'constant' bit on the global. + if (!GNode->isModified() && !I->isConstant()) { + I->setConstant(true); + ++NumGlobalsConstanted; + Changed = true; + } + } + } + return Changed; +} |