tcg: Re-order tcg_region_init vs tcg_prologue_init

Instead of delaying tcg_region_init until after tcg_prologue_init
is complete, do tcg_region_init first and let tcg_prologue_init
shrink the first region by the size of the generated prologue.

Reviewed-by: Luis Pires <luis.pires@eldorado.org.br>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

accel/tcg/tcg-all.c

@@ -111,17 +111,6 @@ static int tcg_init(MachineState *ms)
 
     tcg_exec_init(s->tb_size * 1024 * 1024, s->splitwx_enabled);
     mttcg_enabled = s->mttcg_enabled;
-
-    /*
-     * Initialize TCG regions only for softmmu.
-     *
-     * This needs to be done later for user mode, because the prologue
-     * generation needs to be delayed so that GUEST_BASE is already set.
-     */
-#ifndef CONFIG_USER_ONLY
-    tcg_region_init();
-#endif /* !CONFIG_USER_ONLY */
-
     return 0;
 }
 

accel/tcg/translate-all.c

@@ -1339,6 +1339,9 @@ void tcg_exec_init(unsigned long tb_size, int splitwx)
                                splitwx, &error_fatal);
     assert(ok);
 
+    /* TODO: allocating regions is hand-in-glove with code_gen_buffer. */
+    tcg_region_init();
+
 #if defined(CONFIG_SOFTMMU)
     /* There's no guest base to take into account, so go ahead and
        initialize the prologue now.  */

bsd-user/main.c

@@ -879,7 +879,6 @@ int main(int argc, char **argv)
      * the real value of GUEST_BASE into account.
      */
     tcg_prologue_init(tcg_ctx);
-    tcg_region_init();
 
     /* build Task State */
     memset(ts, 0, sizeof(TaskState));

linux-user/main.c

@@ -868,7 +868,6 @@ int main(int argc, char **argv, char **envp)
        generating the prologue until now so that the prologue can take
        the real value of GUEST_BASE into account.  */
     tcg_prologue_init(tcg_ctx);
-    tcg_region_init();
 
     target_cpu_copy_regs(env, regs);
 

tcg/tcg.c

@@ -1206,32 +1206,18 @@ TranslationBlock *tcg_tb_alloc(TCGContext *s)
 
 void tcg_prologue_init(TCGContext *s)
 {
-    size_t prologue_size, total_size;
-    void *buf0, *buf1;
+    size_t prologue_size;
 
     /* Put the prologue at the beginning of code_gen_buffer.  */
-    buf0 = s->code_gen_buffer;
-    total_size = s->code_gen_buffer_size;
-    s->code_ptr = buf0;
-    s->code_buf = buf0;
+    tcg_region_assign(s, 0);
+    s->code_ptr = s->code_gen_ptr;
+    s->code_buf = s->code_gen_ptr;
     s->data_gen_ptr = NULL;
 
-    /*
-     * The region trees are not yet configured, but tcg_splitwx_to_rx
-     * needs the bounds for an assert.
-     */
-    region.start = buf0;
-    region.end = buf0 + total_size;
-
 #ifndef CONFIG_TCG_INTERPRETER
-    tcg_qemu_tb_exec = (tcg_prologue_fn *)tcg_splitwx_to_rx(buf0);
+    tcg_qemu_tb_exec = (tcg_prologue_fn *)tcg_splitwx_to_rx(s->code_ptr);
 #endif
 
-    /* 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 - TCG_HIGHWATER);
-
 #ifdef TCG_TARGET_NEED_POOL_LABELS
     s->pool_labels = NULL;
 #endif
@@ -1248,32 +1234,32 @@ void tcg_prologue_init(TCGContext *s)
     }
 #endif
 
-    buf1 = s->code_ptr;
+    prologue_size = tcg_current_code_size(s);
+
 #ifndef CONFIG_TCG_INTERPRETER
-    flush_idcache_range((uintptr_t)tcg_splitwx_to_rx(buf0), (uintptr_t)buf0,
-                        tcg_ptr_byte_diff(buf1, buf0));
+    flush_idcache_range((uintptr_t)tcg_splitwx_to_rx(s->code_buf),
+                        (uintptr_t)s->code_buf, prologue_size);
 #endif
 
-    /* Deduct the prologue from the buffer.  */
-    prologue_size = tcg_current_code_size(s);
-    s->code_gen_ptr = buf1;
-    s->code_gen_buffer = buf1;
-    s->code_buf = buf1;
-    total_size -= prologue_size;
-    s->code_gen_buffer_size = total_size;
+    /* Deduct the prologue from the first region.  */
+    region.start = s->code_ptr;
 
-    tcg_register_jit(tcg_splitwx_to_rx(s->code_gen_buffer), total_size);
+    /* Recompute boundaries of the first region. */
+    tcg_region_assign(s, 0);
+
+    tcg_register_jit(tcg_splitwx_to_rx(region.start),
+                     region.end - region.start);
 
 #ifdef DEBUG_DISAS
     if (qemu_loglevel_mask(CPU_LOG_TB_OUT_ASM)) {
         FILE *logfile = qemu_log_lock();
         qemu_log("PROLOGUE: [size=%zu]\n", prologue_size);
         if (s->data_gen_ptr) {
-            size_t code_size = s->data_gen_ptr - buf0;
+            size_t code_size = s->data_gen_ptr - s->code_gen_ptr;
             size_t data_size = prologue_size - code_size;
             size_t i;
 
-            log_disas(buf0, code_size);
+            log_disas(s->code_gen_ptr, code_size);
 
             for (i = 0; i < data_size; i += sizeof(tcg_target_ulong)) {
                 if (sizeof(tcg_target_ulong) == 8) {
@@ -1287,7 +1273,7 @@ void tcg_prologue_init(TCGContext *s)
                 }
             }
         } else {
-            log_disas(buf0, prologue_size);
+            log_disas(s->code_gen_ptr, prologue_size);
         }
         qemu_log("\n");
         qemu_log_flush();