[PULL 6/7] target/nios2: Special case ipending in rdctl and wrctl

[Richard Henderson <richard.henderson@linaro.org>]

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.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/nios2/translate.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/target/nios2/translate.c b/target/nios2/translate.c
index 52965ba17e..a5f8d20729 100644
--- a/target/nios2/translate.c
+++ b/target/nios2/translate.c
@@ -452,6 +452,17 @@ 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, and so we
+         * must perform the AND here, and anywhere else we need the
+         * guest value of ipending.
+         */
+        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 +488,9 @@ 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