[llvm] [llubi] Add support for byval pointer arguments (PR #201852)

[Antonio Frighetto via llvm-commits]

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@@ -1826,10 +1830,61 @@ class InstExecutor : public InstVisitor<InstExecutor, void>,
     for (auto [I, Arg] : enumerate(CB.args())) {
       Type *ArgTy = Arg->getType();
       AnyValue &ArgVal = CalleeArgs[I];
+
       // CallBase::paramHasAttr also checks parameter attributes at known
       // callee. We do it explicitly to avoid duplication.
       AttributeSet AttrsAtCallSite = CB.getParamAttributes(I);
       AttributeSet AttrsAtCallee = Callee->getAttributes().getParamAttrs(I);
+
+      if (ArgTy->isPointerTy()) {
+        auto *ByValTy = AttrsAtCallSite.getByValType();
+        auto *ByValTyFromCallee = AttrsAtCallee.getByValType();
+        if (ByValTy != ByValTyFromCallee) {
+          reportImmediateUB()
+              << "Mismatched byval attribute between callee and callsite.";
+          return;
+        }
+        if (ByValTy) {
+          if (ArgVal.isPoison()) {
+            reportImmediateUB() << "Invalid poison byval pointer argument.";
+            return;
+          }
+
+          uint64_t Size = Ctx.getEffectiveTypeAllocSize(ByValTy);
+          MaybeAlign AllocAlign = AttrsAtCallSite.getAlignment();
+          // Ignore the alignment at the callsite when it is set on the callee.
+          if (MaybeAlign CalleeAlign = AttrsAtCallee.getAlignment())
+            AllocAlign = CalleeAlign;
+          if (!AllocAlign.has_value()) {
+            // If the alignment is not specified, we use the default ABI
+            // alignment. This is the default behavior of
+            // TargetLoweringBase::getByValTypeAlignment.
+            AllocAlign = DL.getABITypeAlign(ByValTy);
+          }
+          // Byval pointers cannot be passed via variadic arguments.
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antoniofrighetto wrote:

Should we assert that byval cannot be on a variadic arg?

https://github.com/llvm/llvm-project/pull/201852