Re: Delay RTL initialization until it is really needed

[Jan Hubicka <hubicka at ucw dot cz>]

> On 06/20/14 01:51, Jan Hubicka wrote:
> >Hi,
> >IRA initialization shows high in profiles even when building lto objects.  This patch simply
> >delays RTL backend initialization until we really decide to output a function.  In some cases
> >this avoids the initialization completely (like in the case of LTO but also user target attributes)
> >and there is some hope for better cache locality.
> >
> >Basic idea is to have two flags saying whether lang and target dependent bits
> >needs initialization and check it when starting function codegen.
> >
> >Bootstrapped/regtested x86_64-linux, testing also at AIX. Ok if it passes?
> >
> >Honza
> >
> >	* toplev.c (backend_init_target): Move init_emit_regs and init_regs to...
> >	(backend_init) ... here; skip ira_init_once and backend_init_target.
> >	(target_reinit) ... and here; clear this_target_rtl->lang_dependent_initialized.
> >	(lang_dependent_init_target): Clear this_target_rtl->lang_dependent_initialized;
> >	break out rtl initialization to ...
> >	(initialize_rtl): ... here; call also backend_init_target and ira_init_once.
> >	* toplev.h (initialize_rtl): New function.
> >	* function.c: Include toplev.h
> >	(init_function_start): Call initialize_rtl.
> >	* rtl.h (target_rtl): Add target_specific_initialized,
> >	lang_dependent_initialized.
> >Index: toplev.c
> >===================================================================
> >--- toplev.c	(revision 211837)
> >+++ toplev.c	(working copy)
> >@@ -1686,6 +1682,31 @@ lang_dependent_init_target (void)
> >       front end is initialized.  It also depends on the HAVE_xxx macros
> >       generated from the target machine description.  */
> >    init_optabs ();
> >+  this_target_rtl->lang_dependent_initialized = false;
> >+}
> >+
> >+/* Perform initializations that are lang-dependent or target-dependent.
> >+   but matters only for late optimizations and RTL generation.  */
> >+
> >+void
> >+initialize_rtl (void)
> >+{
> >+  static int initialized_once;
> >+
> >+  /* Initialization done just once per compilation, but delayed
> >+     till code generation.  */
> >+  if (!initialized_once)
> >+    ira_init_once ();
> >+  initialized_once = true;
> >+
> >+  /* Target specific RTL backend initialization.  */
> >+  if (!this_target_rtl->target_specific_initialized)
> >+    backend_init_target ();
> >+  this_target_rtl->target_specific_initialized = true;
> >+
> >+  if (this_target_rtl->lang_dependent_initialized)
> >+    return;
> >+  this_target_rtl->lang_dependent_initialized = true;
> >
> >    /* The following initialization functions need to generate rtl, so
> >       provide a dummy function context for them.  */
> >@@ -1784,8 +1805,15 @@ target_reinit (void)
> >        regno_reg_rtx = NULL;
> >      }
> >
> >-  /* Reinitialize RTL backend.  */
> >-  backend_init_target ();
> >+  this_target_rtl->lang_dependent_initialized = false;
> Do you want to reset target_specific_initialized here as well?

Actually I meant to only resert target_specific_initialized. 
lang_dependent_initialized is reset few lines later by call
to lang_dependent_init_target.

I am re-testing with this change. OK?

Honza
> 
> 
> 
> Jeff