Added the CloneTrace function which clones traces. It takes a vector of basic blocks, removes

internal phi nodes, and returns a new vector of basic blocks.

llvm-svn: 6431

lib/Transforms/Utils/CloneTrace.cpp

@@ -0,0 +1,83 @@
+//===- CloneTrace.cpp - Clone a trace ---------===//
+//
+// This file implements the CloneTrace interface, which is used 
+// when writing runtime optimizations. It takes a vector of basic blocks
+// removes internal phi nodes, clones the basic blocks, and returns the new
+// vector of basic blocks.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Instruction.h"
+#include "llvm/BasicBlock.h"
+#include "llvm/iPHINode.h"
+#include "llvm/Function.h"
+#include "llvm/Transforms/Utils/Cloning.h"
+#include <map>
+
+
+//Clones the trace (a vector of basic blocks)
+std::vector<BasicBlock *> CloneTrace(std::vector<BasicBlock*> &origTrace) {
+
+  std::vector<BasicBlock *> clonedTrace;
+  std::map<const Value*, Value*> ValueMap;
+  
+  //First, loop over all the Basic Blocks in the trace and copy
+  //them using CloneBasicBlock. Also fix the phi nodes during
+  //this loop. To fix the phi nodes, we delete incoming branches
+  //that are not in the trace.
+  for(std::vector<BasicBlock *>::const_iterator T = origTrace.begin(),
+	End = origTrace.end(); T != End; ++T) {
+
+    //Clone Basic Block
+    BasicBlock *clonedBlock = CloneBasicBlock(*T, ValueMap);
+    
+    //Add it to our new trace
+    clonedTrace.push_back(clonedBlock);
+
+    //Add this new mapping to our Value Map
+    ValueMap[*T] = clonedBlock;
+
+    //Add this cloned BB to the old BB's function
+    (*T)->getParent()->getBasicBlockList().push_back(clonedBlock);
+
+    //Loop over the phi instructions and delete operands
+    //that are from blocks not in the trace
+    //only do this if we are NOT the first block
+    if(T != origTrace.begin()) {
+      for (BasicBlock::iterator I = clonedBlock->begin();
+	   PHINode *PN = dyn_cast<PHINode>(I); ++I) {
+	//get incoming value for the previous BB
+	Value *V = PN->getIncomingValueForBlock(*(T-1));
+	assert(V && "No incoming value from a BasicBlock in our trace!");
+	
+	//remap our phi node to point to incoming value
+	ValueMap[*&I] = V;
+	
+	//remove phi node
+	clonedBlock->getInstList().erase(PN);
+      }
+    }
+  }
+
+  //Second loop to do the remapping
+  for(std::vector<BasicBlock *>::const_iterator BB = clonedTrace.begin(),
+	BE = clonedTrace.end(); BB != BE; ++BB) {
+    for(BasicBlock::iterator I = (*BB)->begin(); I != (*BB)->end(); ++I) {
+      
+      //Loop over all the operands of the instruction
+      for(unsigned op=0, E = I->getNumOperands(); op != E; ++op) {
+	const Value *Op = I->getOperand(op);
+	
+	//Get it out of the value map
+	Value *V = ValueMap[Op];
+
+	//If not in the value map, then its outside our trace so ignore
+	if(V != 0)
+	  I->setOperand(op,V);
+      }
+    }
+  }
+  
+  //return new vector of basic blocks
+  return clonedTrace;
+}