[Attributor] Provide easier checkForallReturnedValues functionality

Summary:
So far, whenever one wants to look at returned values, one had to deal
with the AAReturnedValues and potentially with the AAIsDead attribute.
In the same spirit as other checkForAllXXX methods, we add this
functionality now to the Attributor. By adopting the use sites we got
better results when return instructions were dead.

Reviewers: sstefan1, uenoku

Subscribers: hiraditya, bollu, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65733

llvm-svn: 368222

1 files changed, 85 insertions, 59 deletions

diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
index d25d532d3ef..46dd8b447ec 100644
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -444,6 +444,9 @@ ChangeStatus AANoUnwindImpl::updateImpl(Attributor &A,
 ///
 /// If there is a unique returned value R, the manifest method will:
 ///   - mark R with the "returned" attribute, if R is an argument.
+///
+/// TODO: We should use liveness during construction of the returned values map
+///       and before we set HasOverdefinedReturnedCalls.
 class AAReturnedValuesImpl : public AAReturnedValues, public AbstractState {
 
   /// Mapping of values potentially returned by the associated function to the
@@ -539,13 +542,12 @@ public:
   /// Return an assumed unique return value if a single candidate is found. If
   /// there cannot be one, return a nullptr. If it is not clear yet, return the
   /// Optional::NoneType.
-  Optional<Value *>
-  getAssumedUniqueReturnValue(const AAIsDead *LivenessAA) const;
+  Optional<Value *> getAssumedUniqueReturnValue(Attributor &A) const;
 
-  /// See AbstractState::checkForallReturnedValues(...).
-  bool checkForallReturnedValues(
-      std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)> &Pred)
-      const override;
+  /// See AbstractState::checkForAllReturnedValues(...).
+  bool checkForAllReturnedValuesAndReturnInsts(
+      const function_ref<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)>
+          &Pred) const override;
 
   /// Pretty print the attribute similar to the IR representation.
   const std::string getAsStr() const override;
@@ -582,10 +584,8 @@ ChangeStatus AAReturnedValuesImpl::manifest(Attributor &A) {
   assert(isValidState());
   NumFnKnownReturns++;
 
-  auto *LivenessAA = A.getAAFor<AAIsDead>(*this, getAnchorScope());
-
   // Check if we have an assumed unique return value that we could manifest.
-  Optional<Value *> UniqueRV = getAssumedUniqueReturnValue(LivenessAA);
+  Optional<Value *> UniqueRV = getAssumedUniqueReturnValue(A);
 
   if (!UniqueRV.hasValue() || !UniqueRV.getValue())
     return Changed;
@@ -609,23 +609,16 @@ const std::string AAReturnedValuesImpl::getAsStr() const {
          ")[OD: " + std::to_string(HasOverdefinedReturnedCalls) + "]";
 }
 
-Optional<Value *> AAReturnedValuesImpl::getAssumedUniqueReturnValue(
-    const AAIsDead *LivenessAA) const {
-  // If checkForallReturnedValues provides a unique value, ignoring potential
+Optional<Value *>
+AAReturnedValuesImpl::getAssumedUniqueReturnValue(Attributor &A) const {
+  // If checkForAllReturnedValues provides a unique value, ignoring potential
   // undef values that can also be present, it is assumed to be the actual
   // return value and forwarded to the caller of this method. If there are
   // multiple, a nullptr is returned indicating there cannot be a unique
   // returned value.
   Optional<Value *> UniqueRV;
 
-  std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)> Pred =
-      [&](Value &RV, const SmallPtrSetImpl<ReturnInst *> &RetInsts) -> bool {
-    // If all ReturnInsts are dead, then ReturnValue is dead as well
-    // and can be ignored.
-    if (LivenessAA &&
-        !LivenessAA->isLiveInstSet(RetInsts.begin(), RetInsts.end()))
-      return true;
-
+  auto Pred = [&](Value &RV) -> bool {
     // If we found a second returned value and neither the current nor the saved
     // one is an undef, there is no unique returned value. Undefs are special
     // since we can pretend they have any value.
@@ -642,15 +635,15 @@ Optional<Value *> AAReturnedValuesImpl::getAssumedUniqueReturnValue(
     return true;
   };
 
-  if (!checkForallReturnedValues(Pred))
+  if (!A.checkForAllReturnedValues(getAnchorScope(), Pred, *this))
     UniqueRV = nullptr;
 
   return UniqueRV;
 }
 
-bool AAReturnedValuesImpl::checkForallReturnedValues(
-    std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)> &Pred)
-    const {
+bool AAReturnedValuesImpl::checkForAllReturnedValuesAndReturnInsts(
+    const function_ref<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)>
+        &Pred) const {
   if (!isValidState())
     return false;
 
@@ -728,11 +721,8 @@ ChangeStatus AAReturnedValuesImpl::updateImpl(Attributor &A,
       continue;
     }
 
-    auto *LivenessCSAA = A.getAAFor<AAIsDead>(*this, RetCSAA->getAnchorScope());
-
     // Try to find a assumed unique return value for the called function.
-    Optional<Value *> AssumedUniqueRV =
-        RetCSAA->getAssumedUniqueReturnValue(LivenessCSAA);
+    Optional<Value *> AssumedUniqueRV = RetCSAA->getAssumedUniqueReturnValue(A);
 
     // If no assumed unique return value was found due to the lack of
     // candidates, we may need to resolve more calls (through more update
@@ -1101,14 +1091,10 @@ ChangeStatus AANonNullReturned::updateImpl(Attributor &A,
                                            InformationCache &InfoCache) {
   Function &F = getAnchorScope();
 
-  auto *AARetVal = A.getAAFor<AAReturnedValues>(*this, F);
-  if (!AARetVal)
-    return indicatePessimisticFixpoint();
-
   std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)> Pred =
       this->generatePredicate(A);
 
-  if (!AARetVal->checkForallReturnedValues(Pred))
+  if (!A.checkForAllReturnedValuesAndReturnInsts(F, Pred, *this))
     return indicatePessimisticFixpoint();
   return ChangeStatus::UNCHANGED;
 }
@@ -1342,12 +1328,7 @@ ChangeStatus AANoAliasReturned::updateImpl(Attributor &A,
                                            InformationCache &InfoCache) {
   Function &F = getAnchorScope();
 
-  auto *AARetValImpl = A.getAAFor<AAReturnedValuesImpl>(*this, F);
-  if (!AARetValImpl)
-    return indicatePessimisticFixpoint();
-
-  std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)> Pred =
-      [&](Value &RV, const SmallPtrSetImpl<ReturnInst *> &RetInsts) -> bool {
+  auto CheckReturnValue = [&](Value &RV) -> bool {
     if (Constant *C = dyn_cast<Constant>(&RV))
       if (C->isNullValue() || isa<UndefValue>(C))
         return true;
@@ -1358,11 +1339,11 @@ ChangeStatus AANoAliasReturned::updateImpl(Attributor &A,
     if (!ICS)
       return false;
 
-    auto *NoAliasAA = A.getAAFor<AANoAlias>(*this, RV);
-
-    if (!ICS.returnDoesNotAlias() &&
-        (!NoAliasAA || !NoAliasAA->isAssumedNoAlias()))
-      return false;
+    if (!ICS.returnDoesNotAlias()) {
+      auto *NoAliasAA = A.getAAFor<AANoAlias>(*this, RV);
+      if (!NoAliasAA || !NoAliasAA->isAssumedNoAlias())
+        return false;
+    }
 
     /// FIXME: We can improve capture check in two ways:
     /// 1. Use the AANoCapture facilities.
@@ -1374,7 +1355,7 @@ ChangeStatus AANoAliasReturned::updateImpl(Attributor &A,
     return true;
   };
 
-  if (!AARetValImpl->checkForallReturnedValues(Pred))
+  if (!A.checkForAllReturnedValues(F, CheckReturnValue, *this))
     return indicatePessimisticFixpoint();
 
   return ChangeStatus::UNCHANGED;
@@ -1853,21 +1834,16 @@ AADereferenceableReturned::updateImpl(Attributor &A,
 
   syncNonNull(A.getAAFor<AANonNull>(*this, F));
 
-  auto *AARetVal = A.getAAFor<AAReturnedValues>(*this, F);
-  if (!AARetVal)
-    return indicatePessimisticFixpoint();
-
   bool IsNonNull = isAssumedNonNull();
   bool IsGlobal = isAssumedGlobal();
 
-  std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)> Pred =
-      [&](Value &RV, const SmallPtrSetImpl<ReturnInst *> &RetInsts) -> bool {
+  auto CheckReturnValue = [&](Value &RV) -> bool {
     takeAssumedDerefBytesMinimum(
         computeAssumedDerefenceableBytes(A, RV, IsNonNull, IsGlobal));
     return isValidState();
   };
 
-  if (AARetVal->checkForallReturnedValues(Pred)) {
+  if (A.checkForAllReturnedValues(F, CheckReturnValue, *this)) {
     updateAssumedNonNullGlobalState(IsNonNull, IsGlobal);
     return BeforeState == static_cast<DerefState>(*this)
                ? ChangeStatus::UNCHANGED
@@ -2035,9 +2011,6 @@ struct AAAlignReturned final : AAAlignImpl {
 ChangeStatus AAAlignReturned::updateImpl(Attributor &A,
                                          InformationCache &InfoCache) {
   Function &F = getAnchorScope();
-  auto *AARetValImpl = A.getAAFor<AAReturnedValuesImpl>(*this, F);
-  if (!AARetValImpl)
-    return indicatePessimisticFixpoint();
 
   // Currently, align<n> is deduced if alignments in return values are assumed
   // as greater than n. We reach pessimistic fixpoint if any of the return value
@@ -2045,7 +2018,7 @@ ChangeStatus AAAlignReturned::updateImpl(Attributor &A,
   // optimistic fixpoint is reached earlier.
 
   base_t BeforeState = getAssumed();
-  std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)> Pred =
+  auto CheckReturnValue =
       [&](Value &RV, const SmallPtrSetImpl<ReturnInst *> &RetInsts) -> bool {
     auto *AlignAA = A.getAAFor<AAAlign>(*this, RV);
 
@@ -2059,7 +2032,7 @@ ChangeStatus AAAlignReturned::updateImpl(Attributor &A,
     return isValidState();
   };
 
-  if (!AARetValImpl->checkForallReturnedValues(Pred))
+  if (!A.checkForAllReturnedValuesAndReturnInsts(F, CheckReturnValue, *this))
     return indicatePessimisticFixpoint();
 
   return (getAssumed() != BeforeState) ? ChangeStatus::CHANGED
@@ -2201,7 +2174,7 @@ struct AANoReturnFunction final : AANoReturnImpl {
 
 bool Attributor::checkForAllCallSites(Function &F,
                                       std::function<bool(CallSite)> &Pred,
-                                      AbstractAttribute &QueryingAA,
+                                      const AbstractAttribute &QueryingAA,
                                       bool RequireAllCallSites) {
   // We can try to determine information from
   // the call sites. However, this is only possible all call sites are known,
@@ -2245,9 +2218,62 @@ bool Attributor::checkForAllCallSites(Function &F,
   return true;
 }
 
+bool Attributor::checkForAllReturnedValuesAndReturnInsts(
+    const Function &F,
+    const function_ref<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)>
+        &Pred,
+    const AbstractAttribute &QueryingAA) {
+
+  auto *AARetVal = getAAFor<AAReturnedValues>(QueryingAA, F);
+  if (!AARetVal)
+    return false;
+
+  auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, F);
+  if (!LivenessAA)
+    return AARetVal->checkForAllReturnedValuesAndReturnInsts(Pred);
+
+  auto LivenessFilter = [&](Value &RV,
+                            const SmallPtrSetImpl<ReturnInst *> &ReturnInsts) {
+    SmallPtrSet<ReturnInst *, 4> FilteredReturnInsts;
+    for (ReturnInst *RI : ReturnInsts)
+      if (!LivenessAA->isAssumedDead(RI))
+        FilteredReturnInsts.insert(RI);
+    if (!FilteredReturnInsts.empty())
+      return Pred(RV, FilteredReturnInsts);
+    return true;
+  };
+
+  return AARetVal->checkForAllReturnedValuesAndReturnInsts(LivenessFilter);
+}
+
+bool Attributor::checkForAllReturnedValues(
+    const Function &F, const function_ref<bool(Value &)> &Pred,
+    const AbstractAttribute &QueryingAA) {
+
+  auto *AARetVal = getAAFor<AAReturnedValues>(QueryingAA, F);
+  if (!AARetVal)
+    return false;
+
+  auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, F);
+  if (!LivenessAA)
+    return AARetVal->checkForAllReturnedValuesAndReturnInsts(
+        [&](Value &RV, const SmallPtrSetImpl<ReturnInst *> &) {
+          return Pred(RV);
+        });
+
+  auto LivenessFilter = [&](Value &RV,
+                            const SmallPtrSetImpl<ReturnInst *> &ReturnInsts) {
+    if (LivenessAA->isLiveInstSet(ReturnInsts.begin(), ReturnInsts.end()))
+      return Pred(RV);
+    return true;
+  };
+
+  return AARetVal->checkForAllReturnedValuesAndReturnInsts(LivenessFilter);
+}
+
 bool Attributor::checkForAllInstructions(
     const Function &F, const llvm::function_ref<bool(Instruction &)> &Pred,
-    AbstractAttribute &QueryingAA, InformationCache &InfoCache,
+    const AbstractAttribute &QueryingAA, InformationCache &InfoCache,
     const ArrayRef<unsigned> &Opcodes) {
 
   auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, F);