target/i386/emulate: rework string_rep emulation

Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
Link: https://lore.kernel.org/r/20260223233950.96076-5-mohamed@unpredictable.fr
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/target/i386/emulate/x86_emu.c b/target/i386/emulate/x86_emu.c
index 4409f7bc134bf0b6c60dd37da9a53bd6609a408d..bf96fe06b45727f65ed0596c27193ed7fe4d307b 100644 (file)
--- a/target/i386/emulate/x86_emu.c
+++ b/target/i386/emulate/x86_emu.c
@@ -466,18 +466,25 @@ static inline void string_increment_reg(CPUX86State *env, int reg,
     write_reg(env, reg, val, decode->addressing_size);
 }
 
+static inline int get_ZF(CPUX86State *env) {
+    return env->cc_dst ? 0 : CC_Z;
+}
+
 static inline void string_rep(CPUX86State *env, struct x86_decode *decode,
                               void (*func)(CPUX86State *env,
                                            struct x86_decode *ins), int rep)
 {
     target_ulong rcx = read_reg(env, R_ECX, decode->addressing_size);
-    while (rcx--) {
+
+    while (rcx != 0) {
+        bool is_cmps_or_scas = decode->cmd == X86_DECODE_CMD_CMPS || decode->cmd == X86_DECODE_CMD_SCAS;
         func(env, decode);
+        rcx--;
         write_reg(env, R_ECX, rcx, decode->addressing_size);
-        if ((PREFIX_REP == rep) && !env->cc_dst) {
+        if ((PREFIX_REP == rep) && !get_ZF(env) && is_cmps_or_scas) {
             break;
         }
-        if ((PREFIX_REPN == rep) && env->cc_dst) {
+        if ((PREFIX_REPN == rep) && get_ZF(env)&& is_cmps_or_scas) {
             break;
         }
     }