Add RISC-V test case

Author: lukel97

llvm/test/Transforms/VectorCombine/RISCV/binop-scalarize.ll

@@ -0,0 +1,16 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -S -p vector-combine -mtriple=riscv64 -mattr=+v | FileCheck %s
+
+define <4 x i32> @add_constant_load(ptr %p) {
+; CHECK-LABEL: define <4 x i32> @add_constant_load(
+; CHECK-SAME: ptr [[P:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:    [[X:%.*]] = load i32, ptr [[P]], align 4
+; CHECK-NEXT:    [[V_SCALAR:%.*]] = add i32 [[X]], 42
+; CHECK-NEXT:    [[V:%.*]] = insertelement <4 x i32> poison, i32 [[V_SCALAR]], i64 0
+; CHECK-NEXT:    ret <4 x i32> [[V]]
+;
+  %x = load i32, ptr %p
+  %ins = insertelement <4 x i32> poison, i32 %x, i32 0
+  %v = add <4 x i32> %ins, splat (i32 42)
+  ret <4 x i32> %v
+}