[llvm] [AMDGPU] Compiler should synthesize private buffer resource descriptor from flat_scratch_init (PR #79586)

[Scott Linder via llvm-commits]

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@@ -485,7 +485,7 @@ void SIFrameLowering::emitEntryFunctionFlatScratchInit(
         addReg(FlatScrInitHi).
         addImm(int16_t(AMDGPU::Hwreg::ID_FLAT_SCR_HI |
                        (31 << AMDGPU::Hwreg::WIDTH_M1_SHIFT_)));
-      return;
+      return FlatScratchInitReg;
     }
 
     // For GFX9.
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slinder1 wrote:

Nit: This comment seems like it should just be an `assert` of `ST.getGeneration()`

https://github.com/llvm/llvm-project/pull/79586