+static void completeEphemeralValues(SmallVector<const Value *, 16> &WorkSet,
+ SmallPtrSetImpl<const Value*> &EphValues) {
+ SmallPtrSet<const Value *, 32> Visited;
+
+ // Make sure that all of the items in WorkSet are in our EphValues set.
+ EphValues.insert(WorkSet.begin(), WorkSet.end());
+
+ // Note: We don't speculate PHIs here, so we'll miss instruction chains kept
+ // alive only by ephemeral values.
+
+ while (!WorkSet.empty()) {
+ const Value *V = WorkSet.front();
+ WorkSet.erase(WorkSet.begin());
+
+ if (!Visited.insert(V).second)
+ continue;
+
+ // If all uses of this value are ephemeral, then so is this value.
+ if (!std::all_of(V->user_begin(), V->user_end(),
+ [&](const User *U) { return EphValues.count(U); }))
+ continue;
+
+ EphValues.insert(V);
+ DEBUG(dbgs() << "Ephemeral Value: " << *V << "\n");
+
+ if (const User *U = dyn_cast<User>(V))
+ for (const Value *J : U->operands()) {
+ if (isSafeToSpeculativelyExecute(J))
+ WorkSet.push_back(J);
+ }
+ }
+}
+
+// Find all ephemeral values.
+void CodeMetrics::collectEphemeralValues(
+ const Loop *L, AssumptionCache *AC,
+ SmallPtrSetImpl<const Value *> &EphValues) {
+ SmallVector<const Value *, 16> WorkSet;
+
+ for (auto &AssumeVH : AC->assumptions()) {
+ if (!AssumeVH)
+ continue;
+ Instruction *I = cast<Instruction>(AssumeVH);
+
+ // Filter out call sites outside of the loop so we don't to a function's
+ // worth of work for each of its loops (and, in the common case, ephemeral
+ // values in the loop are likely due to @llvm.assume calls in the loop).
+ if (!L->contains(I->getParent()))
+ continue;
+
+ WorkSet.push_back(I);
+ }
+
+ completeEphemeralValues(WorkSet, EphValues);
+}
+
+void CodeMetrics::collectEphemeralValues(
+ const Function *F, AssumptionCache *AC,
+ SmallPtrSetImpl<const Value *> &EphValues) {
+ SmallVector<const Value *, 16> WorkSet;
+
+ for (auto &AssumeVH : AC->assumptions()) {
+ if (!AssumeVH)
+ continue;
+ Instruction *I = cast<Instruction>(AssumeVH);
+ assert(I->getParent()->getParent() == F &&
+ "Found assumption for the wrong function!");
+ WorkSet.push_back(I);
+ }
+
+ completeEphemeralValues(WorkSet, EphValues);
+}
+