[llvm-commits] CVS: llvm/lib/Analysis/DataStructure/DataStructureOpt.cpp
Chris Lattner
lattner at cs.uiuc.edu
Sat Jun 28 16:56:02 PDT 2003
Changes in directory llvm/lib/Analysis/DataStructure:
DataStructureOpt.cpp added (r1.1)
---
Log message:
New pass to perform DSA based optimizations. Initially we just support turning
globals into constants if we can prove it's safe
---
Diffs of the changes:
Index: llvm/lib/Analysis/DataStructure/DataStructureOpt.cpp
diff -c /dev/null llvm/lib/Analysis/DataStructure/DataStructureOpt.cpp:1.1
*** /dev/null Sat Jun 28 16:55:05 2003
--- llvm/lib/Analysis/DataStructure/DataStructureOpt.cpp Sat Jun 28 16:54:55 2003
***************
*** 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;
+ }
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