[llvm] [RISCV] Reduce code duplication. NFC (PR #171577)

[Craig Topper via llvm-commits]

https://github.com/topperc created https://github.com/llvm/llvm-project/pull/171577

This code only different in the opcodes of the nodes it created.

>From 63bcb927eff87d6d14a20621264217b7e0259ef4 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Wed, 10 Dec 2025 00:09:02 -0800
Subject: [PATCH] [RISCV] Reduce code duplication. NFC

---
 llvm/lib/Target/RISCV/RISCVISelLowering.cpp | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index f28772a74d433..29fc2ddb818b5 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -9786,22 +9786,17 @@ SDValue RISCVTargetLowering::lowerSELECT(SDValue Op, SelectionDAG &DAG) const {
       SDValue ConstVal = IsCZERO_NEZ ? TrueV : FalseV;
       SDValue RegV = IsCZERO_NEZ ? FalseV : TrueV;
       int64_t RawConstVal = cast<ConstantSDNode>(ConstVal)->getSExtValue();
-      // Fall back to XORI if Const == -0x800
-      if (RawConstVal == -0x800) {
-        SDValue XorOp = DAG.getNode(ISD::XOR, DL, VT, RegV, ConstVal);
-        SDValue CMOV =
-            DAG.getNode(IsCZERO_NEZ ? RISCVISD::CZERO_NEZ : RISCVISD::CZERO_EQZ,
-                        DL, VT, XorOp, CondV);
-        return DAG.getNode(ISD::XOR, DL, VT, CMOV, ConstVal);
-      }
       // Efficient only if the constant and its negation fit into `ADDI`
       // Prefer Add/Sub over Xor since can be compressed for small immediates
       if (isInt<12>(RawConstVal)) {
-        SDValue SubOp = DAG.getNode(ISD::SUB, DL, VT, RegV, ConstVal);
-        SDValue CMOV =
+        // Fall back to XORI if Const == -0x800 since we don't have SUBI.
+        unsigned SubOpc = (RawConstVal == -0x800) ? ISD::XOR : ISD::SUB;
+        unsigned AddOpc = (RawConstVal == -0x800) ? ISD::XOR : ISD::ADD;
+        SDValue SubOp = DAG.getNode(SubOpc, DL, VT, RegV, ConstVal);
+        SDValue CZERO =
             DAG.getNode(IsCZERO_NEZ ? RISCVISD::CZERO_NEZ : RISCVISD::CZERO_EQZ,
                         DL, VT, SubOp, CondV);
-        return DAG.getNode(ISD::ADD, DL, VT, CMOV, ConstVal);
+        return DAG.getNode(AddOpc, DL, VT, CZERO, ConstVal);
       }
     }