[llvm] [RISCV] Use vnclip for scalable vector saturating truncation. (PR #88648)

[Luke Lau via llvm-commits]

================
@@ -1166,6 +1166,56 @@ defm : VPatBinarySDNode_VV_VX<usubsat, "PseudoVSSUBU">;
 defm : VPatAVGADD_VV_VX_RM<avgflooru, 0b10>;
 defm : VPatAVGADD_VV_VX_RM<avgceilu, 0b00>;
 
+// 12.5. Vector Narrowing Fixed-Point Clip Instructions
+class VPatTruncSatClipMaxMinSDNodeBase<VTypeInfo vti,
+                                       VTypeInfo wti,
+                                       SDPatternOperator op1,
+                                       int op1_value,
+                                       SDPatternOperator op2,
+                                       int op2_value> :
+  Pat<(vti.Vector (riscv_trunc_vector_vl
+        (wti.Vector (op1
+          (wti.Vector (op2 (wti.Vector wti.RegClass:$rs1),
+            (wti.Vector (riscv_vmv_v_x_vl (wti.Vector undef), op2_value, (XLenVT srcvalue))))),
+          (wti.Vector (riscv_vmv_v_x_vl (wti.Vector undef), op1_value, (XLenVT srcvalue))))),
+        (vti.Mask V0), VLOpFrag)),
+      (!cast<Instruction>("PseudoVNCLIP_WI_"#vti.LMul.MX#"_MASK")
+        (vti.Vector (IMPLICIT_DEF)), wti.RegClass:$rs1, 0,
+        (vti.Mask V0), 0, GPR:$vl, vti.Log2SEW, TA_MA)>;
+
+class VPatTruncSatClipUMinSDNode<VTypeInfo vti,
+                                 VTypeInfo wti,
+                                 int uminval> :
+  Pat<(vti.Vector (riscv_trunc_vector_vl
+        (wti.Vector (umin (wti.Vector wti.RegClass:$rs1),
+          (wti.Vector (riscv_vmv_v_x_vl (wti.Vector undef), uminval, (XLenVT srcvalue))))), (vti.Mask V0), VLOpFrag)),
+      (!cast<Instruction>("PseudoVNCLIPU_WI_"#vti.LMul.MX#"_MASK")
+        (vti.Vector (IMPLICIT_DEF)), wti.RegClass:$rs1, 0,
+        (vti.Mask V0), 0, GPR:$vl, vti.Log2SEW, TA_MA)>;
+
+multiclass VPatTruncSatClipMaxMinSDNode<VTypeInfo vti, VTypeInfo wti,
+  SDPatternOperator max, int maxval, SDPatternOperator min, int minval> {
+    def : VPatTruncSatClipMaxMinSDNodeBase<vti, wti, max, maxval, min, minval>;
+    def : VPatTruncSatClipMaxMinSDNodeBase<vti, wti, min, minval, max, maxval>;
----------------
lukel97 wrote:

Nit, do we need this base multiclass? Would it be easier to just move these two defs inline beside the VPatTruncSatClipUMinSDNode def?

https://github.com/llvm/llvm-project/pull/88648