[llvm] a8610d7 - [Attributor] Move recursion reasoning into `AA::isPotentiallyReachable`

[Johannes Doerfert via llvm-commits]

Author: Johannes Doerfert
Date: 2022-04-05T20:49:03-05:00
New Revision: a8610d752306b48f914eb21108f2d1cb1fd6b710

URL: https://github.com/llvm/llvm-project/commit/a8610d752306b48f914eb21108f2d1cb1fd6b710
DIFF: https://github.com/llvm/llvm-project/commit/a8610d752306b48f914eb21108f2d1cb1fd6b710.diff

LOG: [Attributor] Move recursion reasoning into `AA::isPotentiallyReachable`

With D106397 we ensured that `AAReachability` will not answer queries for
potentially recursive functions. This was necessary as we did not treat
recursion explicitly otherwise. Now that we have
`AA::isPotentiallyReachable` we can make `AAReachability` a purely
intra-procedural AA which does not care about recursion.
`AA::isPotentiallyReachable`, however, does already deal with "going
back" the call graph and can now do so for potentially recursive
functions.

Added: 
    

Modified: 
    llvm/lib/Transforms/IPO/Attributor.cpp
    llvm/lib/Transforms/IPO/AttributorAttributes.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
index d2c965308cb6c..489914b27ccae 100644
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -519,6 +519,8 @@ isPotentiallyReachable(Attributor &A, const Instruction &FromI,
   SmallVector<const Instruction *> Worklist;
   Worklist.push_back(&FromI);
 
+  const auto &NoRecurseAA = A.getAAFor<AANoRecurse>(
+      QueryingAA, IRPosition::function(ToFn), DepClassTy::OPTIONAL);
   while (!Worklist.empty()) {
     const Instruction *CurFromI = Worklist.pop_back_val();
     if (!Visited.insert(CurFromI).second)
@@ -538,7 +540,8 @@ isPotentiallyReachable(Attributor &A, const Instruction &FromI,
                         << *ToI << " [Intra]\n");
       if (Result)
         return true;
-      continue;
+      if (NoRecurseAA.isAssumedNoRecurse())
+        continue;
     }
 
     // TODO: If we can go arbitrarily backwards we will eventually reach an

diff  --git a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
index fc9794632e19d..b8c48648d24c8 100644
--- a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
+++ b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
@@ -3071,10 +3071,6 @@ struct AAReachabilityImpl : AAReachability {
 
   /// See AbstractAttribute::updateImpl(...).
   ChangeStatus updateImpl(Attributor &A) override {
-    const auto &NoRecurseAA = A.getAAFor<AANoRecurse>(
-        *this, IRPosition::function(*getAnchorScope()), DepClassTy::REQUIRED);
-    if (!NoRecurseAA.isAssumedNoRecurse())
-      return indicatePessimisticFixpoint();
     return ChangeStatus::UNCHANGED;
   }
 };
@@ -3306,12 +3302,6 @@ struct AANoAliasCallSiteArgument final : AANoAliasImpl {
         return true;
 
       if (ScopeFn) {
-        const auto &ReachabilityAA = A.getAAFor<AAReachability>(
-            *this, IRPosition::function(*ScopeFn), DepClassTy::OPTIONAL);
-
-        if (!ReachabilityAA.isAssumedReachable(A, *UserI, *getCtxI()))
-          return true;
-
         if (auto *CB = dyn_cast<CallBase>(UserI)) {
           if (CB->isArgOperand(&U)) {
 
@@ -3325,6 +3315,9 @@ struct AANoAliasCallSiteArgument final : AANoAliasImpl {
               return true;
           }
         }
+
+        if (!AA::isPotentiallyReachable(A, *UserI, *getCtxI(), *this))
+          return true;
       }
 
       // For cases which can potentially have more users