[LegalizeVectorTypes] Allow illegal indices when splitting extract_vector_elt

[tlively]

Summary

Fixes PR40267, in which the removed assertion was triggering on
perfectly valid IR. As far as I can tell, constant out of bounds
indices should be allowed when splitting extract_vector_elt, since
they will simply be propagated as out of bounds indices in the
resulting split vector and handled appropriately elsewhere.

llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

 
 SDValue DAGTypeLegalizer::SplitVecOp_EXTRACT_VECTOR_ELT(SDNode *N) {
   SDValue Vec = N->getOperand(0);
   SDValue Idx = N->getOperand(1);
   EVT VecVT = Vec.getValueType();
 
   if (isa<ConstantSDNode>(Idx)) {
     uint64_t IdxVal = cast<ConstantSDNode>(Idx)->getZExtValue();
-    assert(IdxVal < VecVT.getVectorNumElements() && "Invalid vector index!");
 
     SDValue Lo, Hi;
     GetSplitVector(Vec, Lo, Hi);
 
     uint64_t LoElts = Lo.getValueType().getVectorNumElements();
 
     if (IdxVal < LoElts)
       return SDValue(DAG.UpdateNodeOperands(N, Lo, Idx), 0);

llvm/trunk/test/CodeGen/WebAssembly/PR40267.ll

+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers
+
+; Regression test for PR40267. Tests that invalid indices in
+; extract_vector_elt can be handled when vectors ops are split. Notice
+; that SIMD is not enabled for this test. Check only that llc does not
+; crash, since it would previously trigger an assertion.
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown"
+
+define void @foo() {
+  %L6 = load i32, i32* undef
+  br label %BB1
+
+BB1:                                              ; preds = %BB1, %0
+  %bj = select <4 x i1> <i1 true, i1 true, i1 false, i1 false>, <4 x i32> <i32 55, i32 21, i32 92, i32 68>, <4 x i32> <i32 51, i32 61, i32 62, i32 39>
+  %E1 = extractelement <4 x i32> %bj, i32 0
+  %E23 = extractelement <4 x i32> zeroinitializer, i32 %E1
+  %I33 = insertelement <4 x i32> undef, i32 %E23, i1 undef
+  store <4 x i32> %I33, <4 x i32>* undef
+  br label %BB1
+}