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Reapply "[PR16756] Use SSAUpdaterBulk in JumpThreading."

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Stage3/stage4 bootstrap miscompares should be fixed by a non-determinism
fix in IDF (r332167).

This reverts commit r330446.

llvm-svn: 332168
This commit is contained in:
Michael Zolotukhin 2018-05-12 01:52:36 +00:00
parent 92ef96c2e3
commit d5d6cef4d5
1 changed files with 30 additions and 26 deletions
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56
lib/Transforms/Scalar/JumpThreading.cpp
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@ -66,6 +66,7 @@
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#include "llvm/Transforms/Utils/SSAUpdaterBulk.h"
#include "llvm/Transforms/Utils/ValueMapper.h"
#include <algorithm>
#include <cassert>
@ -1996,19 +1997,33 @@ bool JumpThreadingPass::ThreadEdge(BasicBlock *BB,
// PHI nodes for NewBB now.
AddPHINodeEntriesForMappedBlock(SuccBB, BB, NewBB, ValueMapping);
// Update the terminator of PredBB to jump to NewBB instead of BB. This
// eliminates predecessors from BB, which requires us to simplify any PHI
// nodes in BB.
TerminatorInst *PredTerm = PredBB->getTerminator();
for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i)
if (PredTerm->getSuccessor(i) == BB) {
BB->removePredecessor(PredBB, true);
PredTerm->setSuccessor(i, NewBB);
}
// If there were values defined in BB that are used outside the block, then we
// now have to update all uses of the value to use either the original value,
// the cloned value, or some PHI derived value. This can require arbitrary
// PHI insertion, of which we are prepared to do, clean these up now.
SSAUpdater SSAUpdate;
SmallVector<Use*, 16> UsesToRename;
SSAUpdaterBulk SSAUpdate;
for (Instruction &I : *BB) {
SmallVector<Use*, 16> UsesToRename;
// Scan all uses of this instruction to see if it is used outside of its
// block, and if so, record them in UsesToRename.
// block, and if so, record them in UsesToRename. Also, skip phi operands
// from PredBB - we'll remove them anyway.
for (Use &U : I.uses()) {
Instruction *User = cast<Instruction>(U.getUser());
if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
if (UserPN->getIncomingBlock(U) == BB)
if (UserPN->getIncomingBlock(U) == BB ||
UserPN->getIncomingBlock(U) == PredBB)
continue;
} else if (User->getParent() == BB)
continue;
@ -2019,35 +2034,24 @@ bool JumpThreadingPass::ThreadEdge(BasicBlock *BB,
// If there are no uses outside the block, we're done with this instruction.
if (UsesToRename.empty())
continue;
unsigned VarNum = SSAUpdate.AddVariable(I.getName(), I.getType());
DEBUG(dbgs() << "JT: Renaming non-local uses of: " << I << "\n");
// We found a use of I outside of BB. Rename all uses of I that are outside
// its block to be uses of the appropriate PHI node etc. See ValuesInBlocks
// with the two values we know.
SSAUpdate.Initialize(I.getType(), I.getName());
SSAUpdate.AddAvailableValue(BB, &I);
SSAUpdate.AddAvailableValue(NewBB, ValueMapping[&I]);
while (!UsesToRename.empty())
SSAUpdate.RewriteUse(*UsesToRename.pop_back_val());
DEBUG(dbgs() << "\n");
// We found a use of I outside of BB - we need to rename all uses of I that
// are outside its block to be uses of the appropriate PHI node etc.
SSAUpdate.AddAvailableValue(VarNum, BB, &I);
SSAUpdate.AddAvailableValue(VarNum, NewBB, ValueMapping[&I]);
for (auto *U : UsesToRename)
SSAUpdate.AddUse(VarNum, U);
}
// Ok, NewBB is good to go. Update the terminator of PredBB to jump to
// NewBB instead of BB. This eliminates predecessors from BB, which requires
// us to simplify any PHI nodes in BB.
TerminatorInst *PredTerm = PredBB->getTerminator();
for (unsigned i = 0, e = PredTerm->getNumSuccessors(); i != e; ++i)
if (PredTerm->getSuccessor(i) == BB) {
BB->removePredecessor(PredBB, true);
PredTerm->setSuccessor(i, NewBB);
}
DDT->applyUpdates({{DominatorTree::Insert, NewBB, SuccBB},
{DominatorTree::Insert, PredBB, NewBB},
{DominatorTree::Delete, PredBB, BB}});
// Apply all updates we queued with DDT and get the updated Dominator Tree.
DominatorTree *DT = &DDT->flush();
SSAUpdate.RewriteAllUses(DT);
// At this point, the IR is fully up to date and consistent. Do a quick scan
// over the new instructions and zap any that are constants or dead. This
// frequently happens because of phi translation.