target/microblaze: avoid integer overflow in next_page PC check

If the PC is in the last page of the address space, next_page_start
overflows to 0. Fix it.
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Cc: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
Signed-off-by: NEmilio G. Cota <cota@braap.org>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>

target/microblaze/translate.c

@@ -1635,7 +1635,7 @@ void gen_intermediate_code(CPUState *cs, struct TranslationBlock *tb)
     uint32_t pc_start;
     struct DisasContext ctx;
     struct DisasContext *dc = &ctx;
-    uint32_t next_page_start, org_flags;
+    uint32_t page_start, org_flags;
     target_ulong npc;
     int num_insns;
     int max_insns;
@@ -1661,7 +1661,7 @@ void gen_intermediate_code(CPUState *cs, struct TranslationBlock *tb)
         cpu_abort(cs, "Microblaze: unaligned PC=%x\n", pc_start);
     }
 
-    next_page_start = (pc_start & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE;
+    page_start = pc_start & TARGET_PAGE_MASK;
     num_insns = 0;
     max_insns = tb_cflags(tb) & CF_COUNT_MASK;
     if (max_insns == 0) {
@@ -1747,7 +1747,7 @@ void gen_intermediate_code(CPUState *cs, struct TranslationBlock *tb)
     } while (!dc->is_jmp && !dc->cpustate_changed
              && !tcg_op_buf_full()
              && !singlestep
-             && (dc->pc < next_page_start)
+             && (dc->pc - page_start < TARGET_PAGE_SIZE)
              && num_insns < max_insns);
 
     npc = dc->pc;