[VP][DAGCombine] Use simplifySelect when combining vp.select.

Author: AinsleySnow

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -12056,6 +12056,13 @@ SDValue DAGCombiner::foldVSelectOfConstants(SDNode *N) {
 }
 
 SDValue DAGCombiner::visitVP_SELECT(SDNode *N) {
+  SDValue N0 = N->getOperand(0);
+  SDValue N1 = N->getOperand(1);
+  SDValue N2 = N->getOperand(2);
+
+  if (SDValue V = DAG.simplifySelect(N0, N1, N2))
+    return V;
+
   if (SDValue V = foldBoolSelectToLogic<VPMatchContext>(N, DAG))
     return V;
 

llvm/test/CodeGen/RISCV/rvv/vselect-vp.ll

@@ -825,3 +825,56 @@ define <vscale x 2 x i1> @select_cond_x_cond(<vscale x 2 x i1> %x, <vscale x 2 x
   %a = call <vscale x 2 x i1> @llvm.vp.select.nxv2i1(<vscale x 2 x i1> %x, <vscale x 2 x i1> %y, <vscale x 2 x i1> %x, i32 %evl)
   ret <vscale x 2 x i1> %a
 }
+
+define <vscale x 2 x i1> @select_undef_T_F(<vscale x 2 x i1> %x, <vscale x 2 x i1> %y, i32 zeroext %evl) {
+; CHECK-LABEL: select_undef_T_F:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vmv1r.v v0, v8
+; CHECK-NEXT:    ret
+  %a = call <vscale x 2 x i1> @llvm.vp.select.nxv2i1(<vscale x 2 x i1> undef, <vscale x 2 x i1> %x, <vscale x 2 x i1> %y, i32 %evl)
+  ret <vscale x 2 x i1> %a
+}
+
+define <vscale x 2 x i1> @select_undef_undef_F(<vscale x 2 x i1> %x, i32 zeroext %evl) {
+; CHECK-LABEL: select_undef_undef_F:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    ret
+  %a = call <vscale x 2 x i1> @llvm.vp.select.nxv2i1(<vscale x 2 x i1> undef, <vscale x 2 x i1> undef, <vscale x 2 x i1> %x, i32 %evl)
+  ret <vscale x 2 x i1> %a
+}
+
+define <vscale x 2 x i1> @select_unknown_undef_F(<vscale x 2 x i1> %x, <vscale x 2 x i1> %y, i32 zeroext %evl) {
+; CHECK-LABEL: select_unknown_undef_F:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vmv1r.v v0, v8
+; CHECK-NEXT:    ret
+  %a = call <vscale x 2 x i1> @llvm.vp.select.nxv2i1(<vscale x 2 x i1> %x, <vscale x 2 x i1> undef, <vscale x 2 x i1> %y, i32 %evl)
+  ret <vscale x 2 x i1> %a
+}
+
+define <vscale x 2 x i1> @select_unknown_T_undef(<vscale x 2 x i1> %x, <vscale x 2 x i1> %y, i32 zeroext %evl) {
+; CHECK-LABEL: select_unknown_T_undef:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vmv1r.v v0, v8
+; CHECK-NEXT:    ret
+  %a = call <vscale x 2 x i1> @llvm.vp.select.nxv2i1(<vscale x 2 x i1> %x, <vscale x 2 x i1> %y, <vscale x 2 x i1> undef, i32 %evl)
+  ret <vscale x 2 x i1> %a
+}
+
+define <vscale x 2 x i1> @select_false_T_F(<vscale x 2 x i1> %x, <vscale x 2 x i1> %y, <vscale x 2 x i1> %z, i32 zeroext %evl) {
+; CHECK-LABEL: select_false_T_F:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vmv1r.v v0, v9
+; CHECK-NEXT:    ret
+  %a = call <vscale x 2 x i1> @llvm.vp.select.nxv2i1(<vscale x 2 x i1> zeroinitializer, <vscale x 2 x i1> %y, <vscale x 2 x i1> %z, i32 %evl)
+  ret <vscale x 2 x i1> %a
+}
+
+define <vscale x 2 x i1> @select_unknown_T_T(<vscale x 2 x i1> %x, <vscale x 2 x i1> %y, i32 zeroext %evl) {
+; CHECK-LABEL: select_unknown_T_T:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vmv1r.v v0, v8
+; CHECK-NEXT:    ret
+  %a = call <vscale x 2 x i1> @llvm.vp.select.nxv2i1(<vscale x 2 x i1> %x, <vscale x 2 x i1> %y, <vscale x 2 x i1> %y, i32 %evl)
+  ret <vscale x 2 x i1> %a
+}