[llvm] [RISCV] Reverse iteration/deletion structure in vsetvli coalescing [NFC] (PR #98936)

[Philip Reames via llvm-commits]

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@@ -1645,24 +1645,23 @@ void RISCVInsertVSETVLI::coalesceVSETVLIs(MachineBasicBlock &MBB) const {
   Used.demandVTYPE();
   SmallVector<MachineInstr*> ToDelete;
 
-  // Update LIS and cleanup dead AVLs given a value which has
-  // has had one use (as an AVL) removed.
-  auto afterDroppedAVLUse = [&](Register OldVLReg) {
+  auto dropAVLUse = [&](MachineOperand &MO) {
+    if (!MO.isReg() || !MO.getReg().isVirtual())
+      return;
+    Register OldVLReg = MO.getReg();
+    MO.setReg(RISCV::NoRegister);
+
     if (LIS)
       LIS->shrinkToUses(&LIS->getInterval(OldVLReg));
 
     MachineInstr *VLOpDef = MRI->getUniqueVRegDef(OldVLReg);
     if (VLOpDef && TII->isAddImmediate(*VLOpDef, OldVLReg) &&
-        MRI->use_nodbg_empty(OldVLReg)) {
-      if (LIS) {
-        LIS->removeInterval(OldVLReg);
-        LIS->RemoveMachineInstrFromMaps(*VLOpDef);
-      }
-      VLOpDef->eraseFromParent();
-    }
+        MRI->use_nodbg_empty(OldVLReg))
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preames wrote:

I believe so.  RegAllocBase.cpp does so, and if that wasn't valid, I imagine we'd have figured that out by now.  

https://github.com/llvm/llvm-project/pull/98936