[RS4GC] Revert optimization attempt due to memory corruption
This change reverts "246133 [RewriteStatepointsForGC] Reduce the number of new instructions for base pointers" and a follow on bugfix 12575.
As pointed out in pr25846, this code suffers from a memory corruption bug. Since I'm (empirically) not going to get back to this any time soon, simply reverting the problematic change is the right answer.
llvm-svn: 261565
diff --git a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
index 4c86eeb..d2eac91 100644
--- a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
+++ b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
@@ -14,7 +14,6 @@
#include "llvm/Pass.h"
#include "llvm/Analysis/CFG.h"
-#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/ADT/SetOperations.h"
#include "llvm/ADT/Statistic.h"
@@ -1025,68 +1024,6 @@
}
- // Now that we're done with the algorithm, see if we can optimize the
- // results slightly by reducing the number of new instructions needed.
- // Arguably, this should be integrated into the algorithm above, but
- // doing as a post process step is easier to reason about for the moment.
- DenseMap<Value *, Value *> ReverseMap;
- SmallPtrSet<Instruction *, 16> NewInsts;
- SmallSetVector<AssertingVH<Instruction>, 16> Worklist;
- // Note: We need to visit the states in a deterministic order. We uses the
- // Keys we sorted above for this purpose. Note that we are papering over a
- // bigger problem with the algorithm above - it's visit order is not
- // deterministic. A larger change is needed to fix this.
- for (auto Pair : States) {
- auto *BDV = Pair.first;
- auto State = Pair.second;
- Value *Base = State.getBase();
- assert(BDV && Base);
- assert(!isKnownBaseResult(BDV) && "why did it get added?");
- assert(isKnownBaseResult(Base) &&
- "must be something we 'know' is a base pointer");
- if (!State.isConflict())
- continue;
-
- ReverseMap[Base] = BDV;
- if (auto *BaseI = dyn_cast<Instruction>(Base)) {
- NewInsts.insert(BaseI);
- Worklist.insert(BaseI);
- }
- }
- auto ReplaceBaseInstWith = [&](Value *BDV, Instruction *BaseI,
- Value *Replacement) {
- // Add users which are new instructions (excluding self references)
- for (User *U : BaseI->users())
- if (auto *UI = dyn_cast<Instruction>(U))
- if (NewInsts.count(UI) && UI != BaseI)
- Worklist.insert(UI);
- // Then do the actual replacement
- NewInsts.erase(BaseI);
- ReverseMap.erase(BaseI);
- BaseI->replaceAllUsesWith(Replacement);
- assert(States.count(BDV));
- assert(States[BDV].isConflict() && States[BDV].getBase() == BaseI);
- States[BDV] = BDVState(BDVState::Conflict, Replacement);
- BaseI->eraseFromParent();
- };
- const DataLayout &DL = cast<Instruction>(def)->getModule()->getDataLayout();
- while (!Worklist.empty()) {
- Instruction *BaseI = Worklist.pop_back_val();
- assert(NewInsts.count(BaseI));
- Value *Bdv = ReverseMap[BaseI];
- if (auto *BdvI = dyn_cast<Instruction>(Bdv))
- if (BaseI->isIdenticalTo(BdvI)) {
- DEBUG(dbgs() << "Identical Base: " << *BaseI << "\n");
- ReplaceBaseInstWith(Bdv, BaseI, Bdv);
- continue;
- }
- if (Value *V = SimplifyInstruction(BaseI, DL)) {
- DEBUG(dbgs() << "Base " << *BaseI << " simplified to " << *V << "\n");
- ReplaceBaseInstWith(Bdv, BaseI, V);
- continue;
- }
- }
-
// Cache all of our results so we can cheaply reuse them
// NOTE: This is actually two caches: one of the base defining value
// relation and one of the base pointer relation! FIXME
@@ -1094,6 +1031,7 @@
auto *BDV = Pair.first;
Value *base = Pair.second.getBase();
assert(BDV && base);
+ assert(!isKnownBaseResult(BDV) && "why did it get added?");
std::string fromstr = cache.count(BDV) ? cache[BDV]->getName() : "none";
DEBUG(dbgs() << "Updating base value cache"
@@ -1102,6 +1040,8 @@
<< " to: " << base->getName() << "\n");
if (cache.count(BDV)) {
+ assert(isKnownBaseResult(base) &&
+ "must be something we 'know' is a base pointer");
// Once we transition from the BDV relation being store in the cache to
// the base relation being stored, it must be stable
assert((!isKnownBaseResult(cache[BDV]) || cache[BDV] == base) &&