Ensure that GT_CNS_VEC is handled in LinearScan::isMatchingConstant (dotnet#70171)

* Ensure that GT_CNS_VEC is handled in LinearScan::isMatchingConstant

* Ensure an Arm64 assert includes GT_CNS_VEC

* Update src/coreclr/jit/codegenarmarch.cpp

Co-authored-by: Egor Bogatov <egorbo@gmail.com>

Co-authored-by: Egor Bogatov <egorbo@gmail.com>

Author: tannergooding

src/coreclr/jit/codegenarmarch.cpp

@@ -144,7 +144,7 @@ void CodeGen::genCodeForTreeNode(GenTree* treeNode)
     if (treeNode->IsReuseRegVal())
     {
         // For now, this is only used for constant nodes.
-        assert((treeNode->OperGet() == GT_CNS_INT) || (treeNode->OperGet() == GT_CNS_DBL));
+        assert(treeNode->OperIs(GT_CNS_INT, GT_CNS_DBL, GT_CNS_VEC));
         JITDUMP("  TreeNode is marked ReuseReg\n");
         return;
     }

src/coreclr/jit/lsra.cpp

@@ -2695,6 +2695,7 @@ bool LinearScan::isMatchingConstant(RegRecord* physRegRecord, RefPosition* refPo
             }
             break;
         }
+
         case GT_CNS_DBL:
         {
             // For floating point constants, the values must be identical, not simply compare
@@ -2706,6 +2707,12 @@ bool LinearScan::isMatchingConstant(RegRecord* physRegRecord, RefPosition* refPo
             }
             break;
         }
+
+        case GT_CNS_VEC:
+        {
+            return GenTreeVecCon::Equals(refPosition->treeNode->AsVecCon(), otherTreeNode->AsVecCon());
+        }
+
         default:
             break;
     }

src/coreclr/jit/lsraxarch.cpp

@@ -147,6 +147,7 @@ int LinearScan::BuildNode(GenTree* tree)
         case GT_CNS_INT:
         case GT_CNS_LNG:
         case GT_CNS_DBL:
+        case GT_CNS_VEC:
         {
             srcCount = 0;
             assert(dstCount == 1);