[PULL v2 05/45] tcg/riscv: Fix reg overlap case in tcg_out_addsub2

[Alistair Francis]

From: Richard Henderson <richard.hender...@linaro.org>

There was a typo using opc_addi instead of opc_add with the
two registers.  While we're at it, simplify the gating test
to al == bl to improve dynamic scheduling even when the
output register does not overlap the inputs.

Reported-by: LIU Zhiwei <zhiwei_...@linux.alibaba.com>
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
Reviewed-by: Alistair Francis <alistair.fran...@wdc.com>
Message-Id: <20221020233836.2341671-1-richard.hender...@linaro.org>
Signed-off-by: Alistair Francis <alistair.fran...@wdc.com>
---
 tcg/riscv/tcg-target.c.inc | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

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,
-- 
2.38.1