1 files changed, 45 insertions, 1 deletions

diff --git a/contrib/llvm-project/llvm/lib/Transforms/IPO/FunctionAttrs.cpp b/contrib/llvm-project/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
index 7c277518b21d..7ebf265e17ba 100644
--- a/contrib/llvm-project/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/contrib/llvm-project/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -76,6 +76,7 @@ STATISTIC(NumReadOnlyArg, "Number of arguments marked readonly");
 STATISTIC(NumWriteOnlyArg, "Number of arguments marked writeonly");
 STATISTIC(NumNoAlias, "Number of function returns marked noalias");
 STATISTIC(NumNonNullReturn, "Number of function returns marked nonnull");
+STATISTIC(NumNoUndefReturn, "Number of function returns marked noundef");
 STATISTIC(NumNoRecurse, "Number of functions marked as norecurse");
 STATISTIC(NumNoUnwind, "Number of functions marked as nounwind");
 STATISTIC(NumNoFree, "Number of functions marked as nofree");
@@ -1279,6 +1280,45 @@ static void addNonNullAttrs(const SCCNodeSet &SCCNodes,
   }
 }
 
+/// Deduce noundef attributes for the SCC.
+static void addNoUndefAttrs(const SCCNodeSet &SCCNodes,
+                            SmallSet<Function *, 8> &Changed) {
+  // Check each function in turn, determining which functions return noundef
+  // values.
+  for (Function *F : SCCNodes) {
+    // Already noundef.
+    if (F->getAttributes().hasRetAttr(Attribute::NoUndef))
+      continue;
+
+    // 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())
+      return;
+
+    // MemorySanitizer assumes that the definition and declaration of a
+    // function will be consistent. A function with sanitize_memory attribute
+    // should be skipped from inference.
+    if (F->hasFnAttribute(Attribute::SanitizeMemory))
+      continue;
+
+    if (F->getReturnType()->isVoidTy())
+      continue;
+
+    if (all_of(*F, [](BasicBlock &BB) {
+          if (auto *Ret = dyn_cast<ReturnInst>(BB.getTerminator())) {
+            // TODO: perform context-sensitive analysis?
+            return isGuaranteedNotToBeUndefOrPoison(Ret->getReturnValue());
+          }
+          return true;
+        })) {
+      F->addRetAttr(Attribute::NoUndef);
+      ++NumNoUndefReturn;
+      Changed.insert(F);
+    }
+  }
+}
+
 namespace {
 
 /// Collects a set of attribute inference requests and performs them all in one
@@ -1629,7 +1669,10 @@ static void addNoRecurseAttrs(const SCCNodeSet &SCCNodes,
     for (auto &I : BB.instructionsWithoutDebug())
       if (auto *CB = dyn_cast<CallBase>(&I)) {
         Function *Callee = CB->getCalledFunction();
-        if (!Callee || Callee == F || !Callee->doesNotRecurse())
+        if (!Callee || Callee == F ||
+            (!Callee->doesNotRecurse() &&
+             !(Callee->isDeclaration() &&
+               Callee->hasFnAttribute(Attribute::NoCallback))))
           // Function calls a potentially recursive function.
           return;
       }
@@ -1785,6 +1828,7 @@ deriveAttrsInPostOrder(ArrayRef<Function *> Functions, AARGetterT &&AARGetter,
   inferConvergent(Nodes.SCCNodes, Changed);
   addNoReturnAttrs(Nodes.SCCNodes, Changed);
   addWillReturn(Nodes.SCCNodes, Changed);
+  addNoUndefAttrs(Nodes.SCCNodes, Changed);
 
   // If we have no external nodes participating in the SCC, we can deduce some
   // more precise attributes as well.