It was never correct to be able to write to ipending.
Until the rest of the irq code is tidied, the read of ipending
will generate an "unnecessary" mask.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/nios2/translate.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/target/nios2/translate.c b/target/nios2/translate.c
index 52965ba17e..b17ce25a36 100644
--- a/target/nios2/translate.c
+++ b/target/nios2/translate.c
@@ -452,6 +452,15 @@ static void rdctl(DisasContext *dc, uint32_t code, uint32_t flags)
     }
 
     switch (instr.imm5 + CR_BASE) {
+    case CR_IPENDING:
+        /*
+         * The value of the ipending register is synthetic.
+         * In hw, this is the AND of a set of hardware irq lines
+         * with the ienable register.  In qemu, we re-use the space
+         * of CR_IPENDING to store the set of irq lines.
+         */
+        tcg_gen_and_tl(cpu_R[instr.c], cpu_R[CR_IPENDING], cpu_R[CR_IENABLE]);
+        break;
     default:
         tcg_gen_mov_tl(cpu_R[instr.c], cpu_R[instr.imm5 + CR_BASE]);
         break;
@@ -477,6 +486,9 @@ static void wrctl(DisasContext *dc, uint32_t code, uint32_t flags)
     case CR_TLBMISC:
         gen_helper_mmu_write_tlbmisc(cpu_env, v);
         break;
+    case CR_IPENDING:
+        /* ipending is read only, writes ignored. */
+        break;
     default:
         tcg_gen_mov_tl(cpu_R[instr.imm5 + CR_BASE], v);
         break;
-- 
2.25.1

On 27/2/22 19:21, Richard Henderson wrote:
> It was never correct to be able to write to ipending.
> Until the rest of the irq code is tidied, the read of ipending
> will generate an "unnecessary" mask.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   target/nios2/translate.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

On Sun, 27 Feb 2022 at 18:25, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> It was never correct to be able to write to ipending.
> Until the rest of the irq code is tidied, the read of ipending
> will generate an "unnecessary" mask.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  target/nios2/translate.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/target/nios2/translate.c b/target/nios2/translate.c
> index 52965ba17e..b17ce25a36 100644
> --- a/target/nios2/translate.c
> +++ b/target/nios2/translate.c
> @@ -452,6 +452,15 @@ static void rdctl(DisasContext *dc, uint32_t code, uint32_t flags)
>      }
>
>      switch (instr.imm5 + CR_BASE) {
> +    case CR_IPENDING:
> +        /*
> +         * The value of the ipending register is synthetic.
> +         * In hw, this is the AND of a set of hardware irq lines
> +         * with the ienable register.  In qemu, we re-use the space
> +         * of CR_IPENDING to store the set of irq lines.

maybe add
"and so we must perform the AND here, and anywhere else we need
the guest value of CR_IPENDING" ?

> +         */
> +        tcg_gen_and_tl(cpu_R[instr.c], cpu_R[CR_IPENDING], cpu_R[CR_IENABLE]);
> +        break;

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM