[llvm] SelectionDAG: Don't pad the source of ADDRSPACECAST if it's legal. (PR #225390)

[via llvm-commits]

https://github.com/sujianIBM created https://github.com/llvm/llvm-project/pull/225390

With this use case `%out = addrspacecast <2 x ptr> %in to <2 x ptr addrspace(1)>` on z/OS, the res type is `v2i32` (illegal) and the source type is `v2i64` (legal).
Padding the source up to `v4i64` makes it illegal on z/OS and breaks the type legalization. 

>From daea9f84eeab62ce29482eb31c34594ec42c6a72 Mon Sep 17 00:00:00 2001
From: Jian Su <jian.su at ibm.com>
Date: Tue, 22 Sep 2026 12:35:16 +0000
Subject: [PATCH] Don't pad the source of ADDRSPACECAST if it's legal.

---
 llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
index 48fc990700b3c..624fa69a6e023 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -6333,12 +6333,13 @@ SDValue DAGTypeLegalizer::WidenVecRes_ADDRSPACECAST(SDNode *N) {
 
   // The source has the same number of elements as the result, so widen it to
   // match WidenVT. It only lives in the widened-vector map if it is itself
-  // widened; otherwise pad it up to the widened element count.
+  // widened; otherwise pad it up to the widened element count
+  // when it is illegal.
   SDValue InOp = N->getOperand(0);
   EVT InVT = InOp.getValueType();
   if (getTypeAction(InVT) == TargetLowering::TypeWidenVector) {
     InOp = GetWidenedVector(InOp);
-  } else {
+  } else if (getTypeAction(InVT) != TargetLowering::TypeLegal) {
     EVT InWidenVT = EVT::getVectorVT(*DAG.getContext(),
                                      InVT.getVectorElementType(), WidenEC);
     InOp = DAG.getInsertSubvector(DL, DAG.getPOISON(InWidenVT), InOp, 0);