tcg: define TCG_HIGHWATER

Will come in handy very soon.

Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/tcg.c

@@ -116,6 +116,8 @@ static int tcg_target_const_match(tcg_target_long val, TCGType type,
 static bool tcg_out_ldst_finalize(TCGContext *s);
 #endif
 
+#define TCG_HIGHWATER 1024
+
 static TCGRegSet tcg_target_available_regs[2];
 static TCGRegSet tcg_target_call_clobber_regs;
 
@@ -430,7 +432,7 @@ void tcg_prologue_init(TCGContext *s)
     /* Compute a high-water mark, at which we voluntarily flush the buffer
        and start over.  The size here is arbitrary, significantly larger
        than we expect the code generation for any one opcode to require.  */
-    s->code_gen_highwater = s->code_gen_buffer + (total_size - 1024);
+    s->code_gen_highwater = s->code_gen_buffer + (total_size - TCG_HIGHWATER);
 
     tcg_register_jit(s->code_gen_buffer, total_size);