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Fix bug: test/Regression/Transforms/ADCE/2002-01-31-UseStuckAround.ll

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Cleanup code a lot


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2547 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-05-07 22:11:39 +00:00
parent 9d5adb0e11
commit ea54ab9cd2
1 changed files with 31 additions and 46 deletions
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69
lib/Transforms/Scalar/ADCE.cpp
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@ -1,12 +1,13 @@
//===- ADCE.cpp - Code to perform agressive dead code elimination ---------===//
//===- ADCE.cpp - Code to perform aggressive dead code elimination --------===//
//
// This file implements "agressive" dead code elimination. ADCE is DCe where
// This file implements "aggressive" dead code elimination. ADCE is DCe where
// values are assumed to be dead until proven otherwise. This is similar to
// SCCP, except applied to the liveness of values.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Type.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/Writer.h"
@ -26,7 +27,7 @@ namespace {
//===----------------------------------------------------------------------===//
// ADCE Class
//
// This class does all of the work of Agressive Dead Code Elimination.
// This class does all of the work of Aggressive Dead Code Elimination.
// It's public interface consists of a constructor and a doADCE() method.
//
class ADCE : public FunctionPass {
@ -41,7 +42,7 @@ class ADCE : public FunctionPass {
public:
const char *getPassName() const { return "Aggressive Dead Code Elimination"; }
// doADCE - Execute the Agressive Dead Code Elimination Algorithm
// doADCE - Execute the Aggressive Dead Code Elimination Algorithm
//
virtual bool runOnFunction(Function *F) {
Func = F; MadeChanges = false;
@ -61,7 +62,7 @@ public:
// The implementation of this class
//
private:
// doADCE() - Run the Agressive Dead Code Elimination algorithm, returning
// doADCE() - Run the Aggressive Dead Code Elimination algorithm, returning
// true if the function was modified.
//
void doADCE(DominanceFrontier &CDG);
@ -91,12 +92,12 @@ private:
} // End of anonymous namespace
Pass *createAgressiveDCEPass() {
Pass *createAggressiveDCEPass() {
return new ADCE();
}
// doADCE() - Run the Agressive Dead Code Elimination algorithm, returning
// doADCE() - Run the Aggressive Dead Code Elimination algorithm, returning
// true if the function was modified.
//
void ADCE::doADCE(DominanceFrontier &CDG) {
@ -118,19 +119,16 @@ void ADCE::doADCE(DominanceFrontier &CDG) {
if (I->hasSideEffects() || I->getOpcode() == Instruction::Ret) {
markInstructionLive(I);
} else {
// Check to see if anything is trivially dead
if (I->use_size() == 0 && I->getType() != Type::VoidTy) {
++II; // Increment the inst iterator if the inst wasn't deleted
} else if (isInstructionTriviallyDead(I)) {
// Remove the instruction from it's basic block...
delete BB->getInstList().remove(II);
MadeChanges = true;
continue; // Don't increment the iterator past the current slot
}
}
} else {
++II; // Increment the inst iterator if the inst wasn't deleted
}
}
}
#ifdef DEBUG_ADCE
cerr << "Processing work list\n";
@ -170,11 +168,10 @@ void ADCE::doADCE(DominanceFrontier &CDG) {
// Loop over all of the operands of the live instruction, making sure that
// they are known to be alive as well...
//
for (unsigned op = 0, End = I->getNumOperands(); op != End; ++op) {
for (unsigned op = 0, End = I->getNumOperands(); op != End; ++op)
if (Instruction *Operand = dyn_cast<Instruction>(I->getOperand(op)))
markInstructionLive(Operand);
}
}
#ifdef DEBUG_ADCE
cerr << "Current Function: X = Live\n";
@ -192,30 +189,20 @@ void ADCE::doADCE(DominanceFrontier &CDG) {
std::set<BasicBlock*> VisitedBlocks;
BasicBlock *EntryBlock = fixupCFG(Func->front(), VisitedBlocks, AliveBlocks);
if (EntryBlock && EntryBlock != Func->front()) {
if (isa<PHINode>(EntryBlock->front())) {
// Cannot make the first block be a block with a PHI node in it! Instead,
// strip the first basic block of the function to contain no instructions,
// then add a simple branch to the "real" entry node...
//
BasicBlock *E = Func->front();
if (!isa<TerminatorInst>(E->front()) || // Check for an actual change...
cast<TerminatorInst>(E->front())->getNumSuccessors() != 1 ||
cast<TerminatorInst>(E->front())->getSuccessor(0) != EntryBlock) {
E->getInstList().delete_all(); // Delete all instructions in block
E->getInstList().push_back(new BranchInst(EntryBlock));
MadeChanges = true;
}
AliveBlocks.insert(E);
// Next we need to change any PHI nodes in the entry block to refer to the
// new predecessor node...
} else {
// We need to move the new entry block to be the first bb of the function
Function::iterator EBI = find(Func->begin(), Func->end(), EntryBlock);
std::swap(*EBI, *Func->begin()); // Exchange old location with start of fn
MadeChanges = true;
while (PHINode *PN = dyn_cast<PHINode>(EntryBlock->front())) {
assert(PN->getNumIncomingValues() == 1 &&
"Can only have a single incoming value at this point...");
// The incoming value must be outside of the scope of the function, a
// global variable, constant or parameter maybe...
//
PN->replaceAllUsesWith(PN->getIncomingValue(0));
// Nuke the phi node...
delete EntryBlock->getInstList().remove(EntryBlock->begin());
}
}
@ -271,14 +258,12 @@ BasicBlock *ADCE::fixupCFG(BasicBlock *BB, std::set<BasicBlock*> &VisitedBlocks,
if (AliveBlocks.count(BB)) { // Is the block alive?
// Yes it's alive: loop through and eliminate all dead instructions in block
for (BasicBlock::iterator II = BB->begin(); II != BB->end()-1; ) {
Instruction *I = *II;
if (!LiveSet.count(I)) { // Is this instruction alive?
for (BasicBlock::iterator II = BB->begin(); II != BB->end()-1; )
if (!LiveSet.count(*II)) { // Is this instruction alive?
// Nope... remove the instruction from it's basic block...
delete BB->getInstList().remove(II);
MadeChanges = true;
continue; // Don't increment II
}
} else {
++II;
}