DAG: Add assert to getNode for EXTRACT_SUBVECTOR indexes

[arsenm]

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.

[arsenm]

• DAG: Handle half spanning extract_subvector in type legalization #154101
• DAG: Avoid creating illegal extract_subvector in legalizer #154100
• DAG: Add assert to getNode for EXTRACT_SUBVECTOR indexes #154099 👈 (View in Graphite)
• AMDGPU: Fix using illegal extract_subvector indexes #154098
• main

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[llvmbot]

@llvm/pr-subscribers-llvm-selectiondag

@llvm/pr-subscribers-backend-amdgpu

Author: Matt Arsenault (arsenm)

Changes

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.

---

Full diff: https://github.com/llvm/llvm-project/pull/154099.diff

2 Files Affected:

• (modified) llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (-2)
• (modified) llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (+2)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 785245b2d9e74..a8985b0a0fd56 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -26094,8 +26094,6 @@ 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)

[RKSimon]

LGTM

[topperc]

LGTM