[llvm] [AMDGPU] Fix hidden kernarg preload count inconsistency (PR #116759)

[Matt Arsenault via llvm-commits]

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@@ -3020,6 +3021,21 @@ SDValue SITargetLowering::LowerFormalArguments(
           NewArg = DAG.getMergeValues({NewArg, Chain}, DL);
         }
       } else {
+        // Hidden arguments that are in the kernel signature must be preloded to
+        // user SGPRs, or loaded via the implicit_arg ptr. Print a diagnostic
+        // error if a hidden argument is in the argument list and is not
+        // preloaded.
+        if (Arg.isOrigArg()) {
+          Argument *OrigArg = Fn.getArg(Arg.getOrigArgIndex());
+          if (OrigArg->hasAttribute("amdgpu-hidden-argument")) {
+            DiagnosticInfoUnsupported NonPreloadHiddenArg(
+                *OrigArg->getParent(),
+                "Hidden argument in kernel signature was not preloaded",
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arsenm wrote:

Start messages with lowercase 

https://github.com/llvm/llvm-project/pull/116759