From: Laurent Vivier <laurent@vivier.eu>

According to Programmer's Reference Manual, if Dc1 and Dc2 specify the
same data register and the comparison fails, memory operand 1 is stored
in the data register.

The current helpers wrote Dc1 then Dc2, leaving operand 2 in the shared
register.

Swap the writeback order for cas2w/cas2l so memory operand 1 wins.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20251226213707.331741-1-laurent@vivier.eu>
(cherry picked from commit 11dac41f2e830bcd7ba74969dc50f5740e3ce7e7)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/target/m68k/op_helper.c b/target/m68k/op_helper.c
index f29ae12af8..b40cc02c65 100644
--- a/target/m68k/op_helper.c
+++ b/target/m68k/op_helper.c
@@ -777,8 +777,8 @@ void HELPER(cas2w)(CPUM68KState *env, uint32_t regs, uint32_t a1, uint32_t a2)
         env->cc_v = c2;
     }
     env->cc_op = CC_OP_CMPW;
-    env->dregs[Dc1] = deposit32(env->dregs[Dc1], 0, 16, l1);
     env->dregs[Dc2] = deposit32(env->dregs[Dc2], 0, 16, l2);
+    env->dregs[Dc1] = deposit32(env->dregs[Dc1], 0, 16, l1);
 }
 
 static void do_cas2l(CPUM68KState *env, uint32_t regs, uint32_t a1, uint32_t a2,
@@ -839,8 +839,8 @@ static void do_cas2l(CPUM68KState *env, uint32_t regs, uint32_t a1, uint32_t a2,
         env->cc_v = c2;
     }
     env->cc_op = CC_OP_CMPL;
-    env->dregs[Dc1] = l1;
     env->dregs[Dc2] = l2;
+    env->dregs[Dc1] = l1;
 }
 
 void HELPER(cas2l)(CPUM68KState *env, uint32_t regs, uint32_t a1, uint32_t a2)
-- 
2.47.3