The add2 code in the tcg_out_addsub2 function doesn't take into account
the case where rl == al == bl. In that case we can't compute the carry
after the addition. As it corresponds to a multiplication by 2, the
carry bit is the bit 31.
While this is a corner case, this prevents x86-64 guests to boot on a
MIPS host.
Cc: Richard Henderson <r...@twiddle.net>
Signed-off-by: Aurelien Jarno <aurel...@aurel32.net>
---
tcg/mips/tcg-target.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/tcg/mips/tcg-target.c b/tcg/mips/tcg-target.c
index 064db46..e97980d 100644
--- a/tcg/mips/tcg-target.c
+++ b/tcg/mips/tcg-target.c
@@ -1271,6 +1271,9 @@ static void tcg_out_addsub2(TCGContext *s, TCGReg rl,
TCGReg rh, TCGReg al,
if (cbl) {
tcg_out_opc_imm(s, OPC_ADDIU, rl, al, bl);
tcg_out_opc_imm(s, OPC_SLTIU, TCG_TMP0, rl, bl);
+ } else if (rl == al && rl == bl) {
+ tcg_out_opc_sa(s, OPC_SRL, TCG_TMP0, al, 31);
+ tcg_out_opc_reg(s, OPC_ADDU, rl, al, bl);
} else {
tcg_out_opc_reg(s, OPC_ADDU, rl, al, bl);
tcg_out_opc_reg(s, OPC_SLTU, TCG_TMP0, rl, (rl == bl ? al : bl));
--
2.1.4
