[llvm] PeepholeOpt: Remove pointless check for subregister def (PR #128850)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/128850

Subregister defs are illegal in SSA

>From fdbc30bc9aa5a8e4f53767fc23ff09d47fa5ac69 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Wed, 26 Feb 2025 16:36:05 +0700
Subject: [PATCH] PeepholeOpt: Remove pointless check for subregister def

Subregister defs are illegal in SSA
---
 llvm/lib/CodeGen/PeepholeOptimizer.cpp | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/llvm/lib/CodeGen/PeepholeOptimizer.cpp b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
index 44aec9bd0f157..cced54fa72819 100644
--- a/llvm/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
@@ -2125,11 +2125,6 @@ ValueTrackerResult ValueTracker::getNextSourceFromPHI() {
   assert(Def->isPHI() && "Invalid definition");
   ValueTrackerResult Res;
 
-  // If we look for a different subreg, bail as we do not support composing
-  // subregs yet.
-  if (Def->getOperand(0).getSubReg() != DefSubReg)
-    return ValueTrackerResult();
-
   // Return all register sources for PHI instructions.
   for (unsigned i = 1, e = Def->getNumOperands(); i < e; i += 2) {
     const MachineOperand &MO = Def->getOperand(i);