[PATCH] gas: Add TC_FRAG_INIT2

[PATCH] gas: Add TC_FRAG_INIT2

[H.J. Lu]

ommit 3ae729d5a4f63740ed9a778960b17c2912b0bbdd
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Wed Mar 7 04:18:45 2018 -0800

    x86: Rewrite NOP generation for fill and alignment

increased MAX_MEM_FOR_RS_ALIGN_CODE to 4095 which resulted in increase
of assembler time and memory usage by 5 times for inputs with many
.p2align directives, which is typical for LTO output.  This patch
introduces TC_FRAG_INIT2 so that MAX_MEM_FOR_RS_ALIGN_CODE can be set
as needed and tracked by backend it so that HANDLE_ALIGN can check the
maximum alignment for each rs_align_code frag.  Wall time to assemble
the same cc1plus.s:

before:

423.78user 0.89system 7:05.71elapsed 99%CPU

after:

102.35user 0.27system 1:42.89elapsed 99%CPU

	PR gas/24165
	* frags.c (frag_var_init): Support TC_FRAG_INIT_WITH_MAX_CHARS.
	* config/tc-i386.h (MAX_MEM_FOR_RS_ALIGN_CODE): Set to
	(alignment ? ((1 << alignment) - 1) : 1)
	(i386_tc_frag_data): Add max_bytes.
	(TC_FRAG_INIT): Renamed to ...
	(TC_FRAG_INIT2): This.  Track max_bytes.
	(HANDLE_ALIGN): Replace MAX_MEM_FOR_RS_ALIGN_CODE with
	 fragP->tc_frag_data.max_bytes.
---
 gas/config/tc-i386.h   |  9 ++++++---
 gas/doc/internals.texi | 13 +++++++------
 gas/frags.c            | 11 ++++++++---
 3 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/gas/config/tc-i386.h b/gas/config/tc-i386.h
index f10b00df9c..bcd8cd7c75 100644
--- a/gas/config/tc-i386.h
+++ b/gas/config/tc-i386.h
@@ -206,7 +206,7 @@ if ((n)									\
     goto around;							\
   }
 
-#define MAX_MEM_FOR_RS_ALIGN_CODE 4095
+#define MAX_MEM_FOR_RS_ALIGN_CODE  (alignment ? ((1 << alignment) - 1) : 1)
 
 void i386_print_statistics (FILE *);
 #define tc_print_statistics i386_print_statistics
@@ -251,6 +251,7 @@ struct i386_tc_frag_data
   enum processor_type isa;
   i386_cpu_flags isa_flags;
   enum processor_type tune;
+  unsigned int max_bytes;
 };
 
 /* We need to emit the right NOP pattern in .align frags.  This is
@@ -258,12 +259,13 @@ struct i386_tc_frag_data
    the isa/tune settings at the time the .align was assembled.  */
 #define TC_FRAG_TYPE struct i386_tc_frag_data
 
-#define TC_FRAG_INIT(FRAGP)					\
+#define TC_FRAG_INIT2(FRAGP, MAX_BYTES)				\
  do								\
    {								\
      (FRAGP)->tc_frag_data.isa = cpu_arch_isa;			\
      (FRAGP)->tc_frag_data.isa_flags = cpu_arch_isa_flags;	\
      (FRAGP)->tc_frag_data.tune = cpu_arch_tune;		\
+     (FRAGP)->tc_frag_data.max_bytes = (MAX_BYTES);		\
    }								\
  while (0)
 
@@ -280,7 +282,8 @@ if (fragP->fr_type == rs_align_code) 					\
     offsetT __count = (fragP->fr_next->fr_address			\
 		       - fragP->fr_address				\
 		       - fragP->fr_fix);				\
-    if (__count > 0 && __count <= MAX_MEM_FOR_RS_ALIGN_CODE)		\
+    if (__count > 0							\
+	&& (unsigned int) __count <= fragP->tc_frag_data.max_bytes)	\
       md_generate_nops (fragP, fragP->fr_literal + fragP->fr_fix,	\
 			__count, 0);					\
   }
diff --git a/gas/doc/internals.texi b/gas/doc/internals.texi
index 00083679bc..c0a3421eef 100644
--- a/gas/doc/internals.texi
+++ b/gas/doc/internals.texi
@@ -1118,10 +1118,11 @@ These fields are defined with the @code{TC_FIX_TYPE} macro.
 A C statement to output target specific debugging information for
 fixup @var{fixp} to @var{stream}.  This macro is called by @code{print_fixup}.
 
-@item TC_FRAG_INIT (@var{fragp})
-@cindex TC_FRAG_INIT
-A C statement to initialize the target specific fields of frag @var{fragp}.
-These fields are defined with the @code{TC_FRAG_TYPE} macro.
+@item TC_FRAG_INIT2 (@var{fragp}, @var{max_bytes})
+@cindex TC_FRAG_INIT2
+A C statement to initialize the target specific fields of frag @var{fragp}
+with maximum number of bytes @var{max_bytes}.  These fields are defined
+with the @code{TC_FRAG_TYPE} macro.
 
 @item md_number_to_chars
 @cindex md_number_to_chars
@@ -1798,8 +1799,8 @@ If you need to emit fixups for the opcode field from inspection of the
 relaxable frag, then you need to generate a common frag for both the basic
 opcode and relaxable fields, or you need to provide the frag for the opcode to
 pass to @code{fix_new}.  The latter can be done for example by defining
-@code{TC_FRAG_TYPE} to include a pointer to it and defining @code{TC_FRAG_INIT}
-to set the pointer.
+@code{TC_FRAG_TYPE} to include a pointer to it and defining
+@code{TC_FRAG_INIT2} to set the pointer.
 
 Sometimes @code{fr_var} is increased instead, and @code{frag_wane} is not
 called.  I'm not sure, but I think this is to keep @code{fr_fix} referring to
diff --git a/gas/frags.c b/gas/frags.c
index 0ee31078ca..6d270d404b 100644
--- a/gas/frags.c
+++ b/gas/frags.c
@@ -218,6 +218,13 @@ frag_more (size_t nchars)
   return retval;
 }
 \f
+#if !defined (TC_FRAG_INIT2) && defined (TC_FRAG_INIT)
+# define TC_FRAG_INIT2(FRAGP, MAX_BYTES) TC_FRAG_INIT (FRAGP)
+#endif
+#ifndef TC_FRAG_INIT2
+# define TC_FRAG_INIT2(FRAGP, MAX_BYTES)
+#endif
+
 /* Close the current frag, setting its fields for a relaxable frag.  Start a
    new frag.  */
 
@@ -237,9 +244,7 @@ frag_var_init (relax_stateT type, size_t max_chars, size_t var,
   frag_now->fr_cgen.opindex = 0;
   frag_now->fr_cgen.opinfo = 0;
 #endif
-#ifdef TC_FRAG_INIT
-  TC_FRAG_INIT (frag_now);
-#endif
+  TC_FRAG_INIT2 (frag_now, max_chars);
   frag_now->fr_file = as_where (&frag_now->fr_line);
 
   frag_new (max_chars);
-- 
2.20.1

Re: [PATCH] gas: Add TC_FRAG_INIT2

[Alan Modra]

On Sat, Feb 09, 2019 at 06:19:09AM -0800, H.J. Lu wrote:
> 	PR gas/24165
> 	* frags.c (frag_var_init): Support TC_FRAG_INIT_WITH_MAX_CHARS.
> 	* config/tc-i386.h (MAX_MEM_FOR_RS_ALIGN_CODE): Set to
> 	(alignment ? ((1 << alignment) - 1) : 1)
> 	(i386_tc_frag_data): Add max_bytes.
> 	(TC_FRAG_INIT): Renamed to ...
> 	(TC_FRAG_INIT2): This.  Track max_bytes.
> 	(HANDLE_ALIGN): Replace MAX_MEM_FOR_RS_ALIGN_CODE with
> 	 fragP->tc_frag_data.max_bytes.

The idea is good, but I think it would be better to just add another
parameter to TC_FRAG_INIT and update target code rather than
introducing TC_FRAG_INIT2.  I'll preapprove a patch to do that.  It's
not a huge amount of work, and you'll be tidying ARM and AARCH64 which
already sneak max_chars into their init_frag functions.

-- 
Alan Modra
Australia Development Lab, IBM

[PATCH] gas: Pass max_bytes to TC_FRAG_INIT

[H.J. Lu]

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On Sat, Feb 9, 2019 at 6:01 PM Alan Modra <amodra@gmail.com> wrote:
>
> On Sat, Feb 09, 2019 at 06:19:09AM -0800, H.J. Lu wrote:
> >       PR gas/24165
> >       * frags.c (frag_var_init): Support TC_FRAG_INIT_WITH_MAX_CHARS.
> >       * config/tc-i386.h (MAX_MEM_FOR_RS_ALIGN_CODE): Set to
> >       (alignment ? ((1 << alignment) - 1) : 1)
> >       (i386_tc_frag_data): Add max_bytes.
> >       (TC_FRAG_INIT): Renamed to ...
> >       (TC_FRAG_INIT2): This.  Track max_bytes.
> >       (HANDLE_ALIGN): Replace MAX_MEM_FOR_RS_ALIGN_CODE with
> >        fragP->tc_frag_data.max_bytes.
>
> The idea is good, but I think it would be better to just add another
> parameter to TC_FRAG_INIT and update target code rather than
> introducing TC_FRAG_INIT2.  I'll preapprove a patch to do that.  It's
> not a huge amount of work, and you'll be tidying ARM and AARCH64 which
> already sneak max_chars into their init_frag functions.
>

This is the patch I am checking in.

Thanks.

-- 
H.J.

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