[RISCV][NFC] Use sub to construct RVV registers without V0

[wangpc-pp]

This reduces some lines.

[llvmbot]

@llvm/pr-subscribers-backend-risc-v

Author: Wang Pengcheng (wangpc-pp)

Changes

This reduces some lines.

---

Full diff: https://github.com/llvm/llvm-project/pull/82962.diff

1 Files Affected:

• (modified) llvm/lib/Target/RISCV/RISCVRegisterInfo.td (+6-10)

diff --git a/llvm/lib/Target/RISCV/RISCVRegisterInfo.td b/llvm/lib/Target/RISCV/RISCVRegisterInfo.td
index 193b85e2818607..381e0082c49b0b 100644
--- a/llvm/lib/Target/RISCV/RISCVRegisterInfo.td
+++ b/llvm/lib/Target/RISCV/RISCVRegisterInfo.td
@@ -512,25 +512,21 @@ def VR : VReg<!listconcat(VM1VTs, VMaskVTs),
               (add (sequence "V%u", 8, 31),
                    (sequence "V%u", 0, 7)), 1>;
 
-def VRNoV0 : VReg<!listconcat(VM1VTs, VMaskVTs),
-                  (add (sequence "V%u", 8, 31),
-                       (sequence "V%u", 1, 7)), 1>;
+def VRNoV0 : VReg<!listconcat(VM1VTs, VMaskVTs), (sub VR, V0), 1>;
 
 def VRM2 : VReg<VM2VTs, (add (sequence "V%uM2", 8, 31, 2),
                              (sequence "V%uM2", 0, 7, 2)), 2>;
 
-def VRM2NoV0 : VReg<VM2VTs, (add (sequence "V%uM2", 8, 31, 2),
-                                 (sequence "V%uM2", 2, 7, 2)), 2>;
+def VRM2NoV0 : VReg<VM2VTs, (sub VRM2, V0M2), 2>;
 
-def VRM4 : VReg<VM4VTs,
-             (add V8M4, V12M4, V16M4, V20M4, V24M4, V28M4, V0M4, V4M4), 4>;
+def VRM4 : VReg<VM4VTs, (add V8M4, V12M4, V16M4, V20M4,
+                             V24M4, V28M4, V0M4, V4M4), 4>;
 
-def VRM4NoV0 : VReg<VM4VTs,
-             (add V8M4, V12M4, V16M4, V20M4, V24M4, V28M4, V4M4), 4>;
+def VRM4NoV0 : VReg<VM4VTs, (sub VRM4, V0M4), 4>;
 
 def VRM8 : VReg<VM8VTs, (add V8M8, V16M8, V24M8, V0M8), 8>;
 
-def VRM8NoV0 : VReg<VM8VTs, (add V8M8, V16M8, V24M8), 8>;
+def VRM8NoV0 : VReg<VM8VTs, (sub VRM8, V0M8), 8>;
 
 def VMV0 : RegisterClass<"RISCV", VMaskVTs, 64, (add V0)> {
   let Size = 64;

[lukel97]

LGTM