[llvm] [AMDGPU] Change handling of unsupported non-compute shaders with HSA (PR #126798)

[Robert Imschweiler via llvm-commits]

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@@ -2933,7 +2937,7 @@ SDValue SITargetLowering::LowerFormalArguments(
 
   for (unsigned i = 0, e = Ins.size(), ArgIdx = 0; i != e; ++i) {
     const ISD::InputArg &Arg = Ins[i];
-    if (Arg.isOrigArg() && Skipped[Arg.getOrigArgIndex()]) {
+    if ((Arg.isOrigArg() && Skipped[Arg.getOrigArgIndex()]) || IsUnsupportedHsa) {
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ro-i wrote:

> However, I think it would be cleaner to just have a separate loop populating InVals in the error case with the undefs

When I do this:
```c++
  if (Subtarget->isAmdHsaOS() && AMDGPU::isGraphics(CallConv)) {
    DiagnosticInfoUnsupported NoGraphicsHSA(
        Fn, "unsupported non-compute shaders with HSA", DL.getDebugLoc());
    DAG.getContext()->diagnose(NoGraphicsHSA);
    for (unsigned i = 0, e = Ins.size(); i != e; ++i) {
      const ISD::InputArg &Arg = Ins[i];
      InVals.push_back(DAG.getUNDEF(Arg.VT));
    }
    return Chain;
  }
```
I get the following error later:
```llc: ~/git/trunk21.0/llvm-project/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.h:945: void llvm::SIMachineFunctionInfo::setScratchRSrcReg(llvm::Register): Assertion `Reg != 0 && "Should never be unset"' failed.```
I suspect the problem is that the other initialization stuff isn't done because of the early return.

Or are you thinking about something else?

https://github.com/llvm/llvm-project/pull/126798