[llvm] [IR][CodeGen] Specify llvm.gcroot contents are an opaque zero-initialized blob (PR #222333)

[via llvm-commits]

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@@ -6514,14 +6514,10 @@ void Verifier::visitIntrinsicCall(Intrinsic::ID ID, CallBase &Call) {
       auto *AI =
           dyn_cast<AllocaInst>(Call.getArgOperand(0)->stripPointerCasts());
       Check(AI, "llvm.gcroot parameter #1 must be an alloca.", Call);
+      Check(AI->isStaticAlloca(),
+            "llvm.gcroot parameter #1 must be a static alloca.", Call);
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isuckatcs wrote:

These 2 could possible be combined. Also, this now suggests that non-pointer allocas are allowed without metadata, which is once again a behavioral change.

Previously we had an invariant that said "if a root doesn't have a metadata, it is always a pointer". Now that invariant is gone, and the GC has no way to tell what a root without a metadata is.

https://github.com/llvm/llvm-project/pull/222333