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Use the CDG to mark branches alive on demand.

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llvm-svn: 159
This commit is contained in:
Chris Lattner 2001-07-08 18:38:36 +00:00
parent 246d869f71
commit acc906f1de
1 changed files with 42 additions and 18 deletions
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46
lib/Transforms/Scalar/ADCE.cpp
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@ -10,9 +10,10 @@
#include "llvm/Instruction.h"
#include "llvm/Type.h"
#include "llvm/Analysis/Dominators.h"
#include <set>
#include "llvm/Tools/STLExtras.h"
#include "llvm/Analysis/Writer.h"
#include <set>
#include <algorithm>
//===----------------------------------------------------------------------===//
// ADCE Class
@ -47,7 +48,10 @@ private:
WorkList.push_back(I);
}
inline void markTerminatorLive(const BasicBlock *BB) {
cerr << "Marking Term Live\n";
markInstructionLive((Instruction*)BB->back());
}
};
@ -63,15 +67,14 @@ bool ADCE::doADCE() {
for (Method::inst_iterator II = M->inst_begin(); II != M->inst_end(); ) {
Instruction *I = *II;
switch (I->getInstType()) {
case Instruction::Ret:
case Instruction::Call:
case Instruction::Store:
markInstructionLive(I);
break;
default:
if (I->getType() == Type::VoidTy) {
markInstructionLive(I); // Catches terminators and friends
} else {
if (I->use_size() == 0) { // Check to see if anything is trivially dead
// Check to see if anything is trivially dead
if (I->use_size() == 0 && I->getType() != Type::VoidTy) {
// Remove the instruction from it's basic block...
BasicBlock *BB = I->getParent();
delete BB->getInstList().remove(II.getInstructionIterator());
@ -81,24 +84,45 @@ bool ADCE::doADCE() {
continue; // Don't increment the iterator past the current slot
}
}
}
++II; // Increment the iterator
}
// Compute the control dependence graph...
cfg::DominanceFrontier CDG(cfg::DominatorSet(M, true));
cerr << "Processing work list\n";
// AliveBlocks - Set of basic blocks that we know have instructions that are
// alive in them...
//
set<BasicBlock*> AliveBlocks;
// Process the work list of instructions that just became live... if they
// became live, then that means that all of their operands are neccesary as
// well... make them live as well.
//
while (!WorkList.empty()) {
Instruction *I = WorkList.back();
Instruction *I = WorkList.back(); // Get an instruction that became live...
WorkList.pop_back();
for (unsigned op = 0; Value *Op = I->getOperand(op); ++op) {
Instruction *Operand = Op->castInstruction();
BasicBlock *BB = I->getParent();
if (AliveBlocks.count(BB) == 0) { // Basic block not alive yet...
// Mark the basic block as being newly ALIVE... and mark all branches that
// this block is control dependant on as being alive also...
//
AliveBlocks.insert(BB); // Block is now ALIVE!
cfg::DominanceFrontier::const_iterator It = CDG.find(BB);
if (It != CDG.end()) {
// Get the blocks that this node is control dependant on...
const cfg::DominanceFrontier::DomSetType &CDB = It->second;
for_each(CDB.begin(), CDB.end(), // Mark all their terminators as live
bind_obj(this, &ADCE::markTerminatorLive));
}
}
for (unsigned op = 0, End = I->getNumOperands(); op != End; ++op) {
Instruction *Operand = I->getOperand(op)->castInstruction();
if (Operand) markInstructionLive(Operand);
}
}