tcg: Check for overflow via highwater mark

We currently pre-compute an worst case code size for any TB, which
works out to be 122kB.  Since the average TB size is near 1kB, this
wastes quite a lot of storage.

Instead, check for overflow in between generating code for each opcode.
The overhead of the check isn't measurable and wastage is minimized.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/tcg/tcg.h b/tcg/tcg.h
index 5fbbd15660..a696922420 100644
--- a/tcg/tcg.h
+++ b/tcg/tcg.h
@@ -559,10 +559,11 @@ struct TCGContext {
     void *code_gen_prologue;
     void *code_gen_buffer;
     size_t code_gen_buffer_size;
-    /* threshold to flush the translated code buffer */
-    size_t code_gen_buffer_max_size;
     void *code_gen_ptr;
 
+    /* Threshold to flush the translated code buffer.  */
+    void *code_gen_highwater;
+
     TBContext tb_ctx;
 
     /* The TCGBackendData structure is private to tcg-target.c.  */