Re: [Qemu-devel] [PATCH 16/17] s390x: translate engine for s390x CPU

[Peter Maydell]

On 29 March 2011 09:55, Alexander Graf <address@hidden> wrote:
> On 28.03.2011, at 17:40, Peter Maydell wrote:
>> Doesn't this take you over MAX_OP_PER_INSTR for some cases?
>
> I haven't encountered any case where it does.

This untested patch against your v2 ought to make it print
a warning if you do go over the limit:

diff --git a/target-s390x/translate.c b/target-s390x/translate.c
index 6756b84..35a2351 100644
--- a/target-s390x/translate.c
+++ b/target-s390x/translate.c
@@ -5040,7 +5040,7 @@ static inline void
gen_intermediate_code_internal(CPUState *env,
     DisasContext dc;
     target_ulong pc_start;
     uint64_t next_page_start;
-    uint16_t *gen_opc_end;
+    uint16_t *gen_opc_end, *gen_opc_insnstart;
     int j, lj = -1;
     int num_insns, max_insns;
     CPUBreakpoint *bp;
@@ -5070,6 +5070,8 @@ static inline void
gen_intermediate_code_internal(CPUState *env,
     gen_icount_start();

     do {
+        gen_opc_insnstart = gen_opc_ptr;
+
         if (unlikely(!QTAILQ_EMPTY(&env->breakpoints))) {
             QTAILQ_FOREACH(bp, &env->breakpoints, entry) {
                 if (bp->pc == dc.pc) {
@@ -5104,6 +5106,14 @@ static inline void
gen_intermediate_code_internal(CPUState *env,
         if (env->singlestep_enabled) {
             gen_debug(&dc);
         }
+
+        if (gen_opc_ptr > gen_opc_insnstart + MAX_OP_PER_INSTR) {
+            /* Codegen bug, but not a fatal one -- if we really overran the
+             * TCG buffer we will assert later. So just warn.
+             */
+            fprintf(stderr, "Too many TCG ops for insn before "
+                    TARGET_FMT_lx " \n", dc.pc);
+        }
     } while (!dc.is_jmp && gen_opc_ptr < gen_opc_end && dc.pc < next_page_start
              && num_insns < max_insns && !env->singlestep_enabled
              && !singlestep);

I'm not yet sure what the right way to do this generically would be.

-- PMM