[patch 2/5] add hook to track when splitting is complete

[Sandra Loosemore <sandra at codesourcery dot com>]

This patch adds a function to indicate whether the split1 pass has run
yet.  This is used in part 3 of the patch set to decide whether 32-bit
symbolic constant expressions are permitted, e.g. in
TARGET_LEGITIMATE_ADDRESS_P and the movsi expander.

Since there's currently no usable hook for querying the pass manager
where it is relative to another pass, I implemented this using a
target-specific pass that runs directly after split1 and does nothing
but set a flag.

-Sandra

2017-10-19  Sandra Loosemore  <sandra@codesourcery.com>

	gcc/
	* config/nios2/nios2_protos.h (nios2_init_expanders): Declare.
	* config/nios2/nios2.c: Adjust includes.
	(split_completed): New.
	(nios2_symbolic_constant_allowed): New.
	(nios2_init_expanders): New.
	(nios2_postsplit_pass_data): New.
	(class pass_nios2_postsplit): New.
	(make_nios2_postsplit): New.
	(nios2_option_override): Register postsplit pass.
	* config/nios2/nios2.h (INIT_EXPANDERS): Define.

diff --git a/gcc/config/nios2/nios2-protos.h b/gcc/config/nios2/nios2-protos.h
index 4478334..925d46a 100644
--- a/gcc/config/nios2/nios2-protos.h
+++ b/gcc/config/nios2/nios2-protos.h
@@ -28,6 +28,7 @@ extern void nios2_expand_prologue (void);
 extern void nios2_expand_epilogue (bool);
 extern bool nios2_expand_return (void);
 extern void nios2_function_profiler (FILE *, int);
+extern void nios2_init_expanders (void);
 
 #ifdef RTX_CODE
 extern bool nios2_emit_move_sequence (rtx *, machine_mode);
diff --git a/gcc/config/nios2/nios2.c b/gcc/config/nios2/nios2.c
index 659250a..120adb5 100644
--- a/gcc/config/nios2/nios2.c
+++ b/gcc/config/nios2/nios2.c
@@ -47,6 +47,8 @@
 #include "toplev.h"
 #include "langhooks.h"
 #include "stor-layout.h"
+#include "tree-pass.h"
+#include "context.h"
 #include "builtins.h"
 
 /* This file should be included last.  */
@@ -101,6 +103,71 @@ static int custom_code_index[256];
 static bool custom_code_conflict = false;
 
 
+/* Support for target-specific postsplit pass.  */
+
+/* Symbolic constants are split into high/lo_sum pairs during the 
+   split1 pass.  After that, they are not considered legitimate addresses.
+   In order to keep track of whether or not we can generate or recognize
+   symbolic constants, we use a target-specific pass that runs 
+   immediately after split1 and does nothing but set a flag we can check.  */
+
+static bool split_completed = false;
+
+static bool
+nios2_symbolic_constant_allowed (void)
+{
+  /* The reload_completed check is for the benefit of
+     nios2_asm_output_mi_thunk and perhaps other places that try to
+     emulate a post-reload pass.  */
+  return !split_completed && !reload_completed;
+}
+
+/* Use INIT_EXPANDERS to ensure that split_completed is reset before
+   compiling every function.  */
+void
+nios2_init_expanders (void)
+{
+  split_completed = false;
+}
+
+namespace {
+
+static const pass_data nios2_postsplit_pass_data =
+{
+  RTL_PASS,      	// type
+  "nios2_postsplit",	// name
+  OPTGROUP_NONE, 	// optinfo_flags
+  TV_REST_OF_COMPILATION,    // tv_id
+  0,             	// properties_required
+  0,             	// properties_provided
+  0,             	// properties_destroyed
+  0,             	// todo_flags_start
+  0		 	// todo_flags_finish
+};
+
+class pass_nios2_postsplit : public rtl_opt_pass
+{
+ public:
+  pass_nios2_postsplit (gcc::context *ctxt)
+    : rtl_opt_pass (nios2_postsplit_pass_data, ctxt)
+  {}
+
+  virtual unsigned int execute (function *)
+    {
+      split_completed = true;
+      return 0;
+    }
+};
+
+} /* Anonymous namespace */
+
+rtl_opt_pass *
+make_nios2_postsplit (gcc::context *ctxt)
+{
+  return new pass_nios2_postsplit (ctxt);
+}
+
+
 /* Definition of builtin function types for nios2.  */
 
 #define N2_FTYPES				\
@@ -1407,6 +1474,12 @@ nios2_option_override (void)
 
   nios2_custom_check_insns ();
 
+  /* Register target-specific passes.  */
+  opt_pass *postsplit = make_nios2_postsplit (g);
+  struct register_pass_info finish_split_info
+    = { postsplit, "split1", 1, PASS_POS_INSERT_AFTER };
+  register_pass (&finish_split_info);
+
   /* Save the initial options in case the user does function specific
      options.  */
   target_option_default_node = target_option_current_node
diff --git a/gcc/config/nios2/nios2.h b/gcc/config/nios2/nios2.h
index 10bebfb..d077dc5 100644
--- a/gcc/config/nios2/nios2.h
+++ b/gcc/config/nios2/nios2.h
@@ -503,6 +503,9 @@ do {                                                                    \
 #define ASM_PREFERRED_EH_DATA_FORMAT(CODE, GLOBAL)		\
   (flag_pic ? DW_EH_PE_aligned : DW_EH_PE_sdata4)
 
+/* Target-specific initialization.  */
+#define INIT_EXPANDERS nios2_init_expanders ()
+
 /* Misc. parameters.  */
 
 #define STORE_FLAG_VALUE 1