Revert r275027 - Let FuncAttrs infer the 'returned' argument attribute

Reverting r275027 and r275033. These seem to cause miscompiles on the AArch64 buildbot.

llvm-svn: 275042

1 files changed, 0 insertions, 50 deletions

diff --git a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
index 9c9e4822199..fff54408541 100644
--- a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -42,7 +42,6 @@ using namespace llvm;
 STATISTIC(NumReadNone, "Number of functions marked readnone");
 STATISTIC(NumReadOnly, "Number of functions marked readonly");
 STATISTIC(NumNoCapture, "Number of arguments marked nocapture");
-STATISTIC(NumReturned, "Number of arguments marked returned");
 STATISTIC(NumReadNoneArg, "Number of arguments marked readnone");
 STATISTIC(NumReadOnlyArg, "Number of arguments marked readonly");
 STATISTIC(NumNoAlias, "Number of function returns marked noalias");
@@ -484,53 +483,6 @@ determinePointerReadAttrs(Argument *A,
   return IsRead ? Attribute::ReadOnly : Attribute::ReadNone;
 }
 
-/// Deduce returned attributes for the SCC.
-static bool addArgumentReturnedAttrs(const SCCNodeSet &SCCNodes) {
-  bool Changed = false;
-
-  AttrBuilder B;
-  B.addAttribute(Attribute::Returned);
-
-  // Check each function in turn, determining if an argument is always returned.
-  for (Function *F : SCCNodes) {
-    // We can infer and propagate function attributes only when we know that the
-    // definition we'll get at link time is *exactly* the definition we see now.
-    // For more details, see GlobalValue::mayBeDerefined.
-    if (!F->hasExactDefinition())
-      continue;
-
-    if (F->getReturnType()->isVoidTy())
-      continue;
-
-    auto FindRetArg = [&]() -> Value * {
-      Value *RetArg = nullptr;
-      for (BasicBlock &BB : *F)
-        if (auto *Ret = dyn_cast<ReturnInst>(BB.getTerminator())) {
-          // Note that stripPointerCasts should look through functions with
-          // returned arguments.
-          Value *RetVal = Ret->getReturnValue()->stripPointerCasts();
-          if (RetVal->getType() == F->getReturnType() && isa<Argument>(RetVal)) {
-            if (!RetArg)
-              RetArg = RetVal;
-            else if (RetArg != RetVal)
-              return nullptr;
-          }
-        }
-
-      return RetArg;
-    };
-
-    if (Value *RetArg = FindRetArg()) {
-      auto *A = cast<Argument>(RetArg);
-      A->addAttr(AttributeSet::get(F->getContext(), A->getArgNo() + 1, B));
-      ++NumReturned;
-      Changed = true;
-    }
-  }
-
-  return Changed;
-}
-
 /// Deduce nocapture attributes for the SCC.
 static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) {
   bool Changed = false;
@@ -1072,7 +1024,6 @@ PreservedAnalyses PostOrderFunctionAttrsPass::run(LazyCallGraph::SCC &C,
   }
 
   bool Changed = false;
-  Changed |= addArgumentReturnedAttrs(SCCNodes);
   Changed |= addReadAttrs(SCCNodes, AARGetter);
   Changed |= addArgumentAttrs(SCCNodes);
 
@@ -1138,7 +1089,6 @@ static bool runImpl(CallGraphSCC &SCC, AARGetterT AARGetter) {
     SCCNodes.insert(F);
   }
 
-  Changed |= addArgumentReturnedAttrs(SCCNodes);
   Changed |= addReadAttrs(SCCNodes, AARGetter);
   Changed |= addArgumentAttrs(SCCNodes);