[clang] [llvm] [Inliner] Propagate more attributes to params when inlining (PR #91101)

[via llvm-commits]

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@@ -1352,20 +1352,43 @@ static void AddParamAndFnBasicAttributes(const CallBase &CB,
   auto &Context = CalledFunction->getContext();
 
   // Collect valid attributes for all params.
-  SmallVector<AttrBuilder> ValidParamAttrs;
+  SmallVector<AttrBuilder> ValidObjParamAttrs, ValidExactParamAttrs;
   bool HasAttrToPropagate = false;
 
   for (unsigned I = 0, E = CB.arg_size(); I < E; ++I) {
-    ValidParamAttrs.emplace_back(AttrBuilder{CB.getContext()});
+    ValidObjParamAttrs.emplace_back(AttrBuilder{CB.getContext()});
+    ValidExactParamAttrs.emplace_back(AttrBuilder{CB.getContext()});
     // Access attributes can be propagated to any param with the same underlying
     // object as the argument.
     if (CB.paramHasAttr(I, Attribute::ReadNone))
-      ValidParamAttrs.back().addAttribute(Attribute::ReadNone);
+      ValidObjParamAttrs.back().addAttribute(Attribute::ReadNone);
     if (CB.paramHasAttr(I, Attribute::ReadOnly))
-      ValidParamAttrs.back().addAttribute(Attribute::ReadOnly);
+      ValidObjParamAttrs.back().addAttribute(Attribute::ReadOnly);
     if (CB.paramHasAttr(I, Attribute::WriteOnly))
-      ValidParamAttrs.back().addAttribute(Attribute::WriteOnly);
-    HasAttrToPropagate |= ValidParamAttrs.back().hasAttributes();
+      ValidObjParamAttrs.back().addAttribute(Attribute::WriteOnly);
+
+    // Attributes we can only propagate if the exact parameter is forwarded.
+
+    // We can propagate both poison generating an UB generating attributes
+    // without any extra checks. The only attribute that is tricky to propagate
+    // is `noundef` (skipped for now) as that can create new UB where previous
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goldsteinn wrote:

There definitely are cases we can propagate it, but since it need specialized logic I'm keeping separate from this patch.
Next patch hopefully can get no capture, then maybe noundef.

https://github.com/llvm/llvm-project/pull/91101