[llvm] CodeGen: Use getDefBlock in MachineLoop::isLoopInvariant (PR #217018)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/217018

Look up the defining block of an operand's register directly with
getDefBlock() instead of calling getVRegDef() twice and relying on
contains() to walk to the instruction's parent. NFC.

Co-Authored-By: Claude <noreply at anthropic.com> claude-opus-4.8

>From 37d9b726ab69e6245ca9e931182f5f5e8db60010 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Tue, 18 Aug 2026 14:55:06 +0200
Subject: [PATCH] CodeGen: Use getDefBlock in MachineLoop::isLoopInvariant

Look up the defining block of an operand's register directly with
getDefBlock() instead of calling getVRegDef() twice and relying on
contains() to walk to the instruction's parent. NFC.

Co-Authored-By: Claude <noreply at anthropic.com> claude-opus-4.8
---
 llvm/lib/CodeGen/MachineLoopInfo.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/CodeGen/MachineLoopInfo.cpp b/llvm/lib/CodeGen/MachineLoopInfo.cpp
index 3fb0d043b01a1..a6daa5adfaeaa 100644
--- a/llvm/lib/CodeGen/MachineLoopInfo.cpp
+++ b/llvm/lib/CodeGen/MachineLoopInfo.cpp
@@ -286,12 +286,12 @@ bool MachineLoop::isLoopInvariant(MachineInstr &I,
     if (!MO.readsReg())
       continue;
 
-    assert(MRI->getVRegDef(Reg) &&
-           "Machine instr not mapped for this vreg?!");
+    MachineBasicBlock *DefBlock = MRI->getDefBlock(Reg);
+    assert(DefBlock && "Machine instr not mapped for this vreg?!");
 
     // If the loop contains the definition of an operand, then the instruction
     // isn't loop invariant.
-    if (contains(MRI->getVRegDef(Reg)))
+    if (contains(DefBlock))
       return false;
   }