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

[Nikita Popov via cfe-commits]

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@@ -1358,18 +1360,37 @@ 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;
 
+  // Attributes we can only propagate if the exact parameter is forwarded.
+  // We can propagate both poison generating and 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
+  // behavior was just using a poison value.
+  static const Attribute::AttrKind ExactAttrsToPropagate[] = {
+      Attribute::Dereferenceable, Attribute::DereferenceableOrNull,
+      Attribute::NonNull, Attribute::Alignment, Attribute::Range};
+
   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);
-    HasAttrToPropagate |= ValidParamAttrs.back().hasAttributes();
+      ValidObjParamAttrs.back().addAttribute(Attribute::ReadOnly);
+    HasAttrToPropagate |= ValidObjParamAttrs.back().hasAttributes();
+
+    for (Attribute::AttrKind AK : ExactAttrsToPropagate) {
+      Attribute Attr = CB.getParamAttr(I, AK);
+      if (Attr.isValid())
+        ValidExactParamAttrs.back().addAttribute(Attr);
+    }
+
+    HasAttrToPropagate |= ValidObjParamAttrs.back().hasAttributes();
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nikic wrote:

This is already done above, drop one of them.

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