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Fix a bug in Phi-noded insertion. Also, update some comments to reflect what's

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actually going on.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28677 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2006-06-03 23:22:50 +00:00
parent 98bb297da0
commit 30019c88f4
1 changed files with 21 additions and 12 deletions
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33
lib/Transforms/Utils/LCSSA.cpp
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@ -36,9 +36,7 @@
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Support/CFG.h"
#include <algorithm>
#include <cassert>
#include <map>
#include <vector>
using namespace llvm;
@ -69,7 +67,6 @@ namespace {
AU.addRequiredID(LoopSimplifyID);
AU.addPreservedID(LoopSimplifyID);
AU.addRequired<LoopInfo>();
AU.addPreserved<LoopInfo>();
AU.addRequired<DominatorTree>();
AU.addRequired<DominanceFrontier>();
}
@ -137,6 +134,10 @@ void LCSSA::processInstruction(Instruction* Instr,
++NumLCSSA; // We are applying the transformation
std::map<BasicBlock*, Instruction*> Phis;
// Add the base instruction to the Phis list. This makes tracking down
// the dominating values easier when we're filling in Phi nodes. This will
// be removed later, before we perform use replacement.
Phis[Instr->getParent()] = Instr;
// Phi nodes that need to be IDF-processed
@ -150,12 +151,19 @@ void LCSSA::processInstruction(Instruction* Instr,
Phis[*BBI] = phi;
}
// Phi nodes that need to have their incoming values filled.
std::vector<PHINode*> needIncomingValues;
// Calculate the IDF of these LCSSA Phi nodes, inserting new Phi's where
// necessary. Keep track of these new Phi's in Phis.
while (!workList.empty()) {
PHINode *CurPHI = workList.back();
workList.pop_back();
// Even though we've removed this Phi from the work list, we still need
// to fill in its incoming values.
needIncomingValues.push_back(CurPHI);
// Get the current Phi's DF, and insert Phi nodes. Add these new
// nodes to our worklist.
DominanceFrontier::const_iterator it = DF->find(CurPHI->getParent());
@ -172,14 +180,14 @@ void LCSSA::processInstruction(Instruction* Instr,
}
}
}
// Get the predecessor blocks of the current Phi, and use them to hook up
// the operands of the current Phi to any members of DFPhis that dominate
// it. This is a nop for the Phis inserted directly in the exit blocks,
// since they are not dominated by any members of DFPhis.
for (pred_iterator PI = pred_begin(CurPHI->getParent()),
E = pred_end(CurPHI->getParent()); PI != E; ++PI)
CurPHI->addIncoming(getValueDominatingBlock(*PI, Phis),
}
// Fill in all Phis we've inserted that need their incoming values filled in.
for (std::vector<PHINode*>::iterator IVI = needIncomingValues.begin(),
IVE = needIncomingValues.end(); IVI != IVE; ++IVI) {
for (pred_iterator PI = pred_begin((*IVI)->getParent()),
E = pred_end((*IVI)->getParent()); PI != E; ++PI)
(*IVI)->addIncoming(getValueDominatingBlock(*PI, Phis),
*PI);
}
@ -197,7 +205,8 @@ void LCSSA::processInstruction(Instruction* Instr,
Uses.push_back(use);
}
// Deliberately remove the initial instruction from Phis set.
// Deliberately remove the initial instruction from Phis set. It would mess
// up use-replacement.
Phis.erase(Instr->getParent());
for (std::vector<Instruction*>::iterator II = Uses.begin(), IE = Uses.end();