[llvm] [AMDGPU] Support bottom-up postRA scheduing. (PR #135295)

[Harrison Hao via llvm-commits]

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@@ -69,6 +69,10 @@ class GCNHazardRecognizer final : public ScheduleHazardRecognizer {
   // Advance over a MachineInstr bundle. Look for hazards in the bundled
   // instructions.
   void processBundle();
+  // Recede over a MachineInstr bundle. Adds bundled instructions to the
+  // EmittedInstrs queue in bottom-up scheduling mode.
+  // TODO: Hazard detection is not yet implemented.
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harrisonGPU wrote:

Thanks! Should I support all hazard recognizers? I think some older architectures may not need to be supported, since this scheduler is mainly used for graphics. We may only need to support GFX11 and above.
Also, I noticed that some hazard recognizers are specific to older architectures.

https://github.com/llvm/llvm-project/pull/135295