[llvm] [RISCV] Let LiveIntervals::shrinkToUses compute dead immediate. NFC (PR #90629)

[Luke Lau via llvm-commits]

https://github.com/lukel97 created https://github.com/llvm/llvm-project/pull/90629

We can simplify removing dead AVL immediates > 31 by using the dead argument to shrinkToUses, since it will already compute dead values.


>From d25a4d23fbeec04ec261aa9c96ef43189201874a Mon Sep 17 00:00:00 2001
From: Luke Lau <luke at igalia.com>
Date: Wed, 1 May 2024 01:19:56 +0800
Subject: [PATCH] [RISCV] Let LiveIntervals::shrinkToUses compute dead
 immediate. NFC

We can simplify removing dead AVL immediates > 31 by using the dead argument to shrinkToUses, since it will already compute dead values.
---
 llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp b/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
index 216dc78085204e..f4ff17f7b65585 100644
--- a/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
+++ b/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
@@ -1648,17 +1648,9 @@ bool RISCVCoalesceVSETVLI::coalesceVSETVLIs(MachineBasicBlock &MBB) {
           if (NextMI->getOperand(1).isReg())
             NextMI->getOperand(1).setReg(RISCV::NoRegister);
 
-          if (OldVLReg && OldVLReg.isVirtual()) {
-            // NextMI no longer uses OldVLReg so shrink its LiveInterval.
-            LIS->shrinkToUses(&LIS->getInterval(OldVLReg));
-
-            MachineInstr *VLOpDef = MRI->getUniqueVRegDef(OldVLReg);
-            if (VLOpDef && TII->isAddImmediate(*VLOpDef, OldVLReg) &&
-                MRI->use_nodbg_empty(OldVLReg)) {
-              VLOpDef->eraseFromParent();
-              LIS->removeInterval(OldVLReg);
-            }
-          }
+          // NextMI no longer uses OldVLReg so shrink its LiveInterval.
+          if (OldVLReg && OldVLReg.isVirtual())
+            LIS->shrinkToUses(&LIS->getInterval(OldVLReg), &ToDelete);
           MI.setDesc(NextMI->getDesc());
         }
         MI.getOperand(2).setImm(NextMI->getOperand(2).getImm());