[llvm] [AMDGPU] Remove s_delay_alu for VALU->SGPR->SALU (PR #127212)

[Ana Mihajlovic via llvm-commits]

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@@ -377,6 +413,17 @@ class AMDGPUInsertDelayAlu : public MachineFunctionPass {
             }
           }
         }
+
+        if (SII->isVALU(MI.getOpcode())) {
+          for (const auto &Op : MI.defs()) {
+            Register Reg = Op.getReg();
+            if (AMDGPU::isSGPR(Reg, TRI)) {
+              lastSGPRfromVALU = *(TRI->regunits(Reg).begin());
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mihajlovicana wrote:

I tried doing that but this doesn't compile, TRI->regunits(Reg) is a range iterator and doesn't have front, and I can't seem to use [0] either since regunits is not random access

https://github.com/llvm/llvm-project/pull/127212