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[RewriteStatepointsForGC] Fix another order of iteration bug

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It turns out the naming of inserted phis and selects is sensative to the order in which two sets are iterated.  We need to nail this down to avoid non-deterministic output and possible test failures.  

The modified test is the one I first noticed something odd in.  The change is making it more strict to report the error.  With the test change, but without the code change, the test fails roughly 1 in 5.  With the code change, I've run ~30 runs without error.

Long term, the right fix here is to adjust the naming scheme.  I'm checking in this hack to avoid any possible non-determinism in the tests over the weekend.  HJust because I only noticed one case doesn't mean it's actually the only case.  I hope to get to the right change Monday.

std->llvm data structure changes bugfix change #3

llvm-svn: 230835
This commit is contained in:
Philip Reames 2015-02-28 01:52:09 +00:00
parent 5658248d0a
commit 7a2e8f33b1
2 changed files with 21 additions and 5 deletions
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24
lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
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@ -776,10 +776,20 @@ static Value *findBasePointer(Value *I, DefiningValueMapTy &cache,
}
// Insert Phis for all conflicts
// Only changing keys in 'states', thus safe to keep iterators
// We want to keep naming deterministic in the loop that follows, so
// sort the keys before iteration. This is useful in allowing us to
// write stable tests. Note that there is no invalidation issue here.
SmallVector<Value*, 16> Keys;
Keys.reserve(states.size());
for (auto Pair : states) {
Instruction *v = cast<Instruction>(Pair.first);
PhiState state = Pair.second;
Value *V = Pair.first;
Keys.push_back(V);
}
std::sort(Keys.begin(), Keys.end(), order_by_name);
// TODO: adjust naming patterns to avoid this order of iteration dependency
for (Value *V : Keys) {
Instruction *v = cast<Instruction>(V);
PhiState state = states[V];
assert(!isKnownBaseResult(v) && "why did it get added?");
assert(!state.isUnknown() && "Optimistic algorithm didn't complete!");
if (!state.isConflict())
@ -974,7 +984,13 @@ static void findBasePointers(const StatepointLiveSetTy &live,
DenseMap<llvm::Value *, llvm::Value *> &PointerToBase,
DominatorTree *DT, DefiningValueMapTy &DVCache,
DenseSet<llvm::Value *> &NewInsertedDefs) {
for (Value *ptr : live) {
// For the naming of values inserted to be deterministic - which makes for
// much cleaner and more stable tests - we need to assign an order to the
// live values. DenseSets do not provide a deterministic order across runs.
SmallVector<Value*, 64> Temp;
Temp.insert(Temp.end(), live.begin(), live.end());
std::sort(Temp.begin(), Temp.end(), order_by_name);
for (Value *ptr : Temp) {
Value *base = findBasePointer(ptr, DVCache, NewInsertedDefs);
assert(base && "failed to find base pointer");
PointerToBase[ptr] = base;

2
test/Transforms/RewriteStatepointsForGC/base-pointers.ll
View File

@ -76,7 +76,7 @@ loop: ; preds = %loop, %entry
; CHECK-LABEL: loop
; CHECK: %base_phi = phi i64 addrspace(1)*
; CHECK-DAG: [ %base_obj, %entry ]
; CHECK-DAG: [ %base_select
; CHECK-DAG: [ %base_select.relocated, %loop ]
; CHECK-NOT: base_phi2
; CHECK: next = select
; CHECK: base_select