[clang] Propagate lifetimebound from formal parameters to those in the canonical declaration and use that for analysis (PR #107627)

[via cfe-commits]

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@@ -266,6 +262,20 @@ void Sema::inferLifetimeBoundAttribute(FunctionDecl *FD) {
               LifetimeBoundAttr::CreateImplicit(Context, FD->getLocation()));
       }
     }
+  } else if (auto *CanonDecl = FD->getCanonicalDecl(); FD != CanonDecl) {
+    // Propagate the lifetimebound attribute from parameters to the canonical
+    // declaration.
+    // Note that this doesn't include the implicit 'this' parameter, as the
+    // attribute is applied to the function type in that case.
+    const unsigned int NP = std::min(NumParams, CanonDecl->getNumParams());
+    for (unsigned int I = 0; I < NP; ++I) {
+      auto *CanonParam = CanonDecl->getParamDecl(I);
+      if (!CanonParam->hasAttr<LifetimeBoundAttr>() &&
+          FD->getParamDecl(I)->hasAttr<LifetimeBoundAttr>()) {
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higher-performance wrote:

I just tried this but I realized it doesn't work because we want backward propagation to the canonical declaration (since that's what we'll use), rather than forward propagation to the latest one. Unless you're suggesting I change that logic?

https://github.com/llvm/llvm-project/pull/107627