[RISCV] Add test for vmerge.vvm that could have splat sunk. NFC

Author: lukel97

llvm/test/CodeGen/RISCV/rvv/sink-splat-operands.ll

@@ -5423,3 +5423,41 @@ vector.body:                                      ; preds = %vector.body, %entry
 for.cond.cleanup:                                 ; preds = %vector.body
   ret void
 }
+
+define void @sink_splat_select(ptr nocapture %a, i32 signext %x) {
+; CHECK-LABEL: sink_splat_select:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
+; CHECK-NEXT:    vmv.v.x v8, a1
+; CHECK-NEXT:    lui a1, 1
+; CHECK-NEXT:    add a1, a0, a1
+; CHECK-NEXT:    li a2, 42
+; CHECK-NEXT:  .LBB117_1: # %vector.body
+; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    vle32.v v9, (a0)
+; CHECK-NEXT:    vmseq.vx v0, v9, a2
+; CHECK-NEXT:    vmerge.vvm v9, v9, v8, v0
+; CHECK-NEXT:    vse32.v v9, (a0)
+; CHECK-NEXT:    addi a0, a0, 16
+; CHECK-NEXT:    bne a0, a1, .LBB117_1
+; CHECK-NEXT:  # %bb.2: # %for.cond.cleanup
+; CHECK-NEXT:    ret
+entry:
+  %broadcast.splatinsert = insertelement <4 x i32> poison, i32 %x, i32 0
+  %broadcast.splat = shufflevector <4 x i32> %broadcast.splatinsert, <4 x i32> poison, <4 x i32> zeroinitializer
+  br label %vector.body
+
+vector.body:                                      ; preds = %vector.body, %entry
+  %index = phi i64 [ 0, %entry ], [ %index.next, %vector.body ]
+  %0 = getelementptr inbounds i32, ptr %a, i64 %index
+  %load = load <4 x i32>, ptr %0, align 4
+  %cond = icmp eq <4 x i32> %load, splat (i32 42)
+  %1 = select <4 x i1> %cond, <4 x i32> %broadcast.splat, <4 x i32> %load
+  store <4 x i32> %1, ptr %0, align 4
+  %index.next = add nuw i64 %index, 4
+  %2 = icmp eq i64 %index.next, 1024
+  br i1 %2, label %for.cond.cleanup, label %vector.body
+
+for.cond.cleanup:                                 ; preds = %vector.body
+  ret void
+}