An explicit representation of dependence graphs, and a pass that

computes a dependence graph for data dependences on memory locations
using interprocedural Mod/Ref information.

llvm-svn: 4957

1 files changed, 79 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/IPA/DependenceGraph.cpp b/llvm/lib/Analysis/IPA/DependenceGraph.cpp
new file mode 100644
index 00000000000..fa8f7b00041
--- /dev/null
+++ b/llvm/lib/Analysis/IPA/DependenceGraph.cpp
@@ -0,0 +1,79 @@
+//===- DependenceGraph.cpp - Dependence graph for a function ----*- C++ -*-===//
+//
+// This file implments an explicit representation for the dependence graph
+// of a function, with one node per instruction and one edge per dependence.
+// Dependences include both data and control dependences.
+// 
+// Each dep. graph node (class DepGraphNode) keeps lists of incoming and
+// outgoing dependence edges.
+// 
+// Each dep. graph edge (class Dependence) keeps a pointer to one end-point
+// of the dependence.  This saves space and is important because dep. graphs
+// can grow quickly.  It works just fine because the standard idiom is to
+// start with a known node and enumerate the dependences to or from that node.
+//===----------------------------------------------------------------------===//
+
+
+#include "llvm/Analysis/DependenceGraph.h"
+#include "llvm/Function.h"
+#include "llvm/BasicBlock.h"
+#include "llvm/Instruction.h"
+
+
+//----------------------------------------------------------------------------
+// class Dependence:
+// 
+// A representation of a simple (non-loop-related) dependence
+//----------------------------------------------------------------------------
+
+void Dependence::print(std::ostream &O) const
+{
+  assert(depType != NoDependence && "This dependence should never be created!");
+  switch (depType) {
+  case TrueDependence:    O << "TRUE dependence"; break;
+  case AntiDependence:    O << "ANTI dependence"; break;
+  case OutputDependence:  O << "OUTPUT dependence"; break;
+  case ControlDependence: O << "CONTROL dependence"; break;
+  default: assert(0 && "Invalid dependence type"); break;
+  }
+}
+
+
+//----------------------------------------------------------------------------
+// class DepGraphNode
+//----------------------------------------------------------------------------
+
+void DepGraphNode::print(std::ostream &O) const
+{
+  const_iterator DI = outDepBegin(), DE = outDepEnd();
+
+  O << "\nDeps. from instr:" << getInstr();
+
+  for ( ; DI != DE; ++DI)
+    {
+      O << "\t";
+      DI->print(O);
+      O << " to instruction:";
+      O << DI->getSink()->getInstr();
+    }
+}
+
+//----------------------------------------------------------------------------
+// class DependenceGraph
+//----------------------------------------------------------------------------
+
+DependenceGraph::~DependenceGraph()
+{
+  // Free all DepGraphNode objects created for this graph
+  for (map_iterator I = depNodeMap.begin(), E = depNodeMap.end(); I != E; ++I)
+    delete I->second;
+}
+
+void DependenceGraph::print(const Function& func, std::ostream &O) const
+{
+  O << "DEPENDENCE GRAPH FOR FUNCTION " << func.getName() << ":\n";
+  for (Function::const_iterator BB=func.begin(), FE=func.end(); BB != FE; ++BB)
+    for (BasicBlock::const_iterator II=BB->begin(), IE=BB->end(); II !=IE; ++II)
+      if (const DepGraphNode* dgNode = this->getNode(*II))
+        dgNode->print(O);
+}