Re: [PATCH] target/i386: Fix incorrect tcg generation for RCR & RCL instructions

On 5/28/26 8:14 PM, Abhigyan Kumar wrote:
> RCR and RCL instructions of a count of 9 is meaningless for 8-bit
> operands. In gen_RCR and gen_RCL functions, gen_rotc_mod converts a
> rotation of 9 to 0. But, the can_be_zero flag wasn't updated and hence
> we skip the immediate if branch. This causes 0 to underflow into -1 at
> tcg_gen_subi_tl(count, count, 1);
> 
> Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3452
> Signed-off-by: Abhigyan Kumar <[email protected]>
> ---
>   target/i386/tcg/emit.c.inc | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/target/i386/tcg/emit.c.inc b/target/i386/tcg/emit.c.inc
> index ce636b6c5..a71af846d 100644
> --- a/target/i386/tcg/emit.c.inc
> +++ b/target/i386/tcg/emit.c.inc
> @@ -3452,6 +3452,7 @@ static void gen_RCL(DisasContext *s, X86DecodedInsn *decode)
>       low_count = tcg_temp_new();
>   
>       gen_rotc_mod(ot, count);
> +    can_be_zero = (ot == MO_8 || ot == MO_16);
>       have_1bit_cin = gen_eflags_adcox(s, decode, true, can_be_zero);
>       if (can_be_zero) {
>           zero_label = gen_new_label();
> @@ -3504,6 +3505,7 @@ static void gen_RCR(DisasContext *s, X86DecodedInsn *decode)
>       high_count = tcg_temp_new();
>   
>       gen_rotc_mod(ot, count);
> +    can_be_zero = (ot == MO_8 || ot == MO_16);
>       have_1bit_cin = gen_eflags_adcox(s, decode, true, can_be_zero);
>       if (can_be_zero) {
>           zero_label = gen_new_label();

Greetings. It has been over two and a half months since I submitted this 
patch. It's my humble request to know the status of the 
review/acceptance for my patch. Please inform me about any required amends.

Thank you for your patience and attention.

-- 
Abhigyan Kumar