[llvm] [GlobalISel] Fix null deref when target has no stack guard variable (PR #224252)

[via llvm-commits]

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@@ -4907,10 +4907,9 @@ bool IRTranslatorImpl::emitSPDescriptorParent(StackProtectorDescriptor &SPD,
   } else {
     // TODO: test using android subtarget when we support @llvm.thread.pointer.
     const Value *IRGuard = TLI->getSDagStackGuard(M, *Libcalls);
-    if (!IRGuard) {
-      LLVM_DEBUG(dbgs() << "Failed to lower call to stack protector check\n");
-      return false;
-    }
+    if (!IRGuard)
+      reportFatalUsageError("unable to lower stackguard for this backend");
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tfzee wrote:

I didn't see any actual way to construct a poison register but from the lowering of the DAG poison and the code higher up I assume you mean the  buildUndef + getReg.

https://github.com/llvm/llvm-project/pull/224252