[llvm] [X86] combineINSERT_SUBVECTOR - use peekThroughBitcastsAndExtracts helper to match target shuffles as well. NFC. (PR #209803)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon created https://github.com/llvm/llvm-project/pull/209803

We were always checking if the result of peekThroughBitcastsAndExtracts was a target shuffle - so let the helper do it for us.

Makes it easier for future handling of faux shuffles as well.

>From d56f72f31ab3d448a18ba965906762d58bc1a2c7 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev at redking.me.uk>
Date: Wed, 15 Jul 2026 16:49:06 +0100
Subject: [PATCH] [X86] combineINSERT_SUBVECTOR - use
 peekThroughBitcastsAndExtracts helper to match target shuffles as well. NFC.

We were always checking if the result of peekThroughBitcastsAndExtracts was a target shuffle - so let the helper do it for us.

Makes it easier for future handling of faux shuffles as well.
---
 llvm/lib/Target/X86/X86ISelLowering.cpp | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index e02129525dd00..bb4b13e4feca4 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -61527,11 +61527,11 @@ static SDValue combineINSERT_SUBVECTOR(SDNode *N, SelectionDAG &DAG,
     }
   }
 
-  auto peekThroughBitcastsAndExtracts = [](SDValue V) {
+  auto isFoldableAsShuffle = [](SDValue V) {
     while (V.getOpcode() == ISD::BITCAST ||
            V.getOpcode() == ISD::EXTRACT_SUBVECTOR)
       V = V.getOperand(0);
-    return V;
+    return isTargetShuffle(V.getOpcode());
   };
 
   // Match concat_vector style patterns.
@@ -61553,10 +61553,7 @@ static SDValue combineINSERT_SUBVECTOR(SDNode *N, SelectionDAG &DAG,
                          SubVectorOps[0], DAG.getVectorIdxConstant(0, dl));
 
     // Attempt to recursively combine to a shuffle.
-    if (all_of(SubVectorOps, [&](SDValue SubOp) {
-          SubOp = peekThroughBitcastsAndExtracts(SubOp);
-          return isTargetShuffle(SubOp.getOpcode());
-        })) {
+    if (all_of(SubVectorOps, isFoldableAsShuffle)) {
       SDValue Op(N, 0);
       if (SDValue Res = combineX86ShufflesRecursively(Op, DAG, Subtarget))
         return Res;
@@ -61610,8 +61607,7 @@ static SDValue combineINSERT_SUBVECTOR(SDNode *N, SelectionDAG &DAG,
   }
 
   // Attempt to recursively combine to a shuffle.
-  if (isTargetShuffle(peekThroughBitcastsAndExtracts(Vec).getOpcode()) &&
-      isTargetShuffle(peekThroughBitcastsAndExtracts(SubVec).getOpcode())) {
+  if (isFoldableAsShuffle(Vec) && isFoldableAsShuffle(SubVec)) {
     SDValue Op(N, 0);
     if (SDValue Res = combineX86ShufflesRecursively(Op, DAG, Subtarget))
       return Res;