[RISCV][TTI] Add llvm.vp.select into canSplatOperand. (llvm#117982)

The second operand of llvm.vp.select is a splat operand , it can help
llvm.vp.select fold vv instructions to vx instructions.

llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp

@@ -2375,6 +2375,7 @@ bool RISCVTTIImpl::canSplatOperand(Instruction *I, int Operand) const {
   case Intrinsic::vp_ssub_sat:
   case Intrinsic::usub_sat:
   case Intrinsic::vp_usub_sat:
+  case Intrinsic::vp_select:
     return Operand == 1;
     // These intrinsics are commutative.
   case Intrinsic::vp_add:

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

@@ -5498,3 +5498,86 @@ vector.body:                                      ; preds = %vector.body, %entry
 for.cond.cleanup:                                 ; preds = %vector.body
   ret void
 }
+
+define void @sink_splat_vp_select_op1(ptr %a, i32 %x, i32 %vl) {
+; CHECK-LABEL: sink_splat_vp_select_op1:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    lui a4, 1
+; CHECK-NEXT:    li a3, 42
+; CHECK-NEXT:    slli a5, a2, 32
+; CHECK-NEXT:    add a2, a0, a4
+; CHECK-NEXT:    srli a4, a5, 32
+; CHECK-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
+; CHECK-NEXT:  .LBB119_1: # %vector.body
+; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    vle32.v v8, (a0)
+; CHECK-NEXT:    vmseq.vx v0, v8, a3
+; CHECK-NEXT:    vsetvli zero, a4, e32, m1, ta, ma
+; CHECK-NEXT:    vmerge.vxm v8, v8, a1, v0
+; CHECK-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
+; CHECK-NEXT:    vse32.v v8, (a0)
+; CHECK-NEXT:    addi a0, a0, 16
+; CHECK-NEXT:    bne a0, a2, .LBB119_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:
+  %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 = call <4 x i32> @llvm.vp.select(<4 x i1> %cond, <4 x i32> %broadcast.splat, <4 x i32> %load, i32 %vl)
+  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:
+  ret void
+}
+
+define void @sink_splat_vp_select_op2(ptr %a, i32 %x, i32 %vl) {
+; CHECK-LABEL: sink_splat_vp_select_op2:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
+; CHECK-NEXT:    vmv.v.x v8, a1
+; CHECK-NEXT:    lui a3, 1
+; CHECK-NEXT:    li a1, 42
+; CHECK-NEXT:    slli a4, a2, 32
+; CHECK-NEXT:    add a2, a0, a3
+; CHECK-NEXT:    srli a3, a4, 32
+; CHECK-NEXT:  .LBB120_1: # %vector.body
+; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    vle32.v v9, (a0)
+; CHECK-NEXT:    vmseq.vx v0, v9, a1
+; CHECK-NEXT:    vsetvli zero, a3, e32, m1, ta, ma
+; CHECK-NEXT:    vmerge.vvm v9, v8, v9, v0
+; CHECK-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
+; CHECK-NEXT:    vse32.v v9, (a0)
+; CHECK-NEXT:    addi a0, a0, 16
+; CHECK-NEXT:    bne a0, a2, .LBB120_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:
+  %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 = call <4 x i32> @llvm.vp.select(<4 x i1> %cond, <4 x i32> %load, <4 x i32> %broadcast.splat, i32 %vl)
+  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:
+  ret void
+}