[llvm-branch-commits] [llvm] DAG: Add assert to getNode for EXTRACT_SUBVECTOR indexes (PR #154099)

[Matt Arsenault via llvm-branch-commits]

https://github.com/arsenm updated https://github.com/llvm/llvm-project/pull/154099

>From 3fd9c57c7993fb1ad2651a6fe8681cda289e3e27 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Mon, 18 Aug 2025 13:22:26 +0900
Subject: [PATCH] DAG: Add assert to getNode for EXTRACT_SUBVECTOR indexes

Verify it's a multiple of the result vector element count
instead of asserting this in random combines.

The testcase in #153808 fails in the wrong point. Add an
assert to getNode so the invalid extract asserts at construction
instead of use.
---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp  | 2 --
 llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 2 ++
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 43d4138df8b49..9aae043f822a3 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -26091,8 +26091,6 @@ SDValue DAGCombiner::visitEXTRACT_SUBVECTOR(SDNode *N) {
     EVT ConcatSrcVT = V.getOperand(0).getValueType();
     assert(ConcatSrcVT.getVectorElementType() == NVT.getVectorElementType() &&
            "Concat and extract subvector do not change element type");
-    assert((ExtIdx % ExtNumElts) == 0 &&
-           "Extract index is not a multiple of the input vector length.");
 
     unsigned ConcatSrcNumElts = ConcatSrcVT.getVectorMinNumElements();
     unsigned ConcatOpIdx = ExtIdx / ConcatSrcNumElts;
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 84282d8a1c37b..fadf2c7a4b9bc 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -7956,6 +7956,8 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
     assert(N2C->getAPIntValue().getBitWidth() ==
                TLI->getVectorIdxWidth(getDataLayout()) &&
            "Constant index for EXTRACT_SUBVECTOR has an invalid size");
+    assert(N2C->getZExtValue() % VT.getVectorMinNumElements() == 0 &&
+           "Extract index is not a multiple of the output vector length");
 
     // Trivial extraction.
     if (VT == N1VT)