[clang] nonblocking/nonallocating attributes: 2nd pass caller/callee analysis (PR #99656)

[Doug Wyatt via cfe-commits]

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@@ -5137,47 +5137,41 @@ StringRef FunctionEffect::name() const {
   llvm_unreachable("unknown effect kind");
 }
 
-bool FunctionEffect::canInferOnFunction(const Decl &Callee) const {
+std::optional<FunctionEffect> FunctionEffect::effectProhibitingInference(
+    const Decl &Callee, const FunctionEffectKindSet &CalleeFX) const {
   switch (kind()) {
   case Kind::NonAllocating:
   case Kind::NonBlocking: {
-    FunctionEffectsRef CalleeFX;
-    if (auto *FD = Callee.getAsFunction())
-      CalleeFX = FD->getFunctionEffects();
-    else if (auto *BD = dyn_cast<BlockDecl>(&Callee))
-      CalleeFX = BD->getFunctionEffects();
-    else
-      return false;
-    for (const FunctionEffectWithCondition &CalleeEC : CalleeFX) {
+    for (const FunctionEffect &Effect : CalleeFX) {
       // nonblocking/nonallocating cannot call allocating.
-      if (CalleeEC.Effect.kind() == Kind::Allocating)
-        return false;
+      if (Effect.kind() == Kind::Allocating)
+        return Effect;
       // nonblocking cannot call blocking.
-      if (kind() == Kind::NonBlocking &&
-          CalleeEC.Effect.kind() == Kind::Blocking)
-        return false;
+      if (kind() == Kind::NonBlocking && Effect.kind() == Kind::Blocking)
+        return Effect;
     }
-    return true;
+    return std::nullopt;
   }
 
   case Kind::Allocating:
   case Kind::Blocking:
-    return false;
+    assert(0 && "effectProhibitingInference with non-inferable effect kind");
----------------
dougsonos wrote:

Hard experience has trained me to think of `assert()` as a potential no-op, thus the `break`, but yeah, the combination with `llvm_unreachable()` is no good.

https://github.com/llvm/llvm-project/pull/99656