diff --git a/tcg/riscv/tcg-target.c.inc b/tcg/riscv/tcg-target.c.inc
index 191197853f..2a84c57bec 100644
--- a/tcg/riscv/tcg-target.c.inc
+++ b/tcg/riscv/tcg-target.c.inc
@@ -700,9 +700,15 @@ static void tcg_out_addsub2(TCGContext *s,
         if (cbl) {
             tcg_out_opc_imm(s, opc_addi, rl, al, bl);
             tcg_out_opc_imm(s, OPC_SLTIU, TCG_REG_TMP0, rl, bl);
-        } else if (rl == al && rl == bl) {
+        } else if (al == bl) {
+            /*
+             * If the input regs overlap, this is a simple doubling
+             * and carry-out is the input msb.  This special case is
+             * required when the output reg overlaps the input,
+             * but we might as well use it always.
+             */
             tcg_out_opc_imm(s, OPC_SLTI, TCG_REG_TMP0, al, 0);
-            tcg_out_opc_reg(s, opc_addi, rl, al, bl);
+            tcg_out_opc_reg(s, opc_add, rl, al, al);
         } else {
             tcg_out_opc_reg(s, opc_add, rl, al, bl);
             tcg_out_opc_reg(s, OPC_SLTU, TCG_REG_TMP0,