target/nios2: Special case ipending in rdctl and wrctl

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>

diff --git a/target/nios2/translate.c b/target/nios2/translate.c
index 52965ba17ea1407ff9297b6f2d47fdf9dc607ce7..a5f8d2072932fb8c84000ac2d729cc98fbc8ad49 100644 (file)
--- 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;