Updating patch regarding bypassing assembler when generating LTO object files

Updating patch regarding bypassing assembler when generating LTO object files

[Ankur Saini]

Hi,
I have been fiddling around with the patch regarding "bypassing assmebler
while generating slim lto files" and managed to make it build with the
current trunk. Though the patch seems to be working on Linux machine, it
causes an ICE on macOS (it crashes in langhooks.cc while executing
`lhd_begin_section ()`).

here is the patch ( not fully tested and is still a prototype ), I
basically mimicked the entire previous patch (
https://gcc.gnu.org/legacy-ml/gcc/2014-09/msg00340.html ) but on current
source.

- Ankur

--- 

From e5d72a73962c34dcd818c17d440eb98ddd94e624 Mon Sep 17 00:00:00 2001
From: Ankur Saini <arsenic@sourceware.org>
Date: Sun, 8 May 2022 07:03:51 +0530
Subject: [PATCH] bypass-asm prototype: 1

---
 gcc/Makefile.in             |  1 +
 gcc/common.opt              |  3 +++
 gcc/langhooks.cc            | 29 +++++++++++++++++++++++++++-
 gcc/{lto => }/lto-object.cc | 29 +++++++++++++++++++++-------
 gcc/lto-streamer.h          | 35 ++++++++++++++++++++++++++++++++++
 gcc/lto/Make-lang.in        |  4 ++--
 gcc/lto/lto-common.cc       |  3 ++-
 gcc/lto/lto-lang.cc         |  1 +
 gcc/lto/lto.h               | 38 -------------------------------------
 gcc/toplev.cc               | 19 ++++++++++++++++---
 10 files changed, 110 insertions(+), 52 deletions(-)
 rename gcc/{lto => }/lto-object.cc (94%)

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 31ff95500c9..3d1241d5819 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1509,6 +1509,7 @@ OBJS = \
 	lto-section-out.o \
 	lto-opts.o \
 	lto-compress.o \
+	lto-object.o \
 	mcf.o \
 	mode-switching.o \
 	modulo-sched.o \
diff --git a/gcc/common.opt b/gcc/common.opt
index 8a0dafc522d..6348197380d 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1158,6 +1158,9 @@ fbtr-bb-exclusive
 Common Ignore
 Does nothing.  Preserved for backward compatibility.
 
+fbypass-asm=
+Common Joined Var(flag_bypass_asm)
+
 fcallgraph-info
 Common RejectNegative Var(flag_callgraph_info) Init(NO_CALLGRAPH_INFO);
 Output callgraph information on a per-file basis.
diff --git a/gcc/langhooks.cc b/gcc/langhooks.cc
index df970678a08..abfab7a27e0 100644
--- a/gcc/langhooks.cc
+++ b/gcc/langhooks.cc
@@ -38,6 +38,10 @@ along with GCC; see the file COPYING3.  If not see
 #include "stor-layout.h"
 #include "cgraph.h"
 #include "debug.h"
+#include "function.h"
+#include "basic-block.h"
+#include "gimple.h"
+#include "lto-streamer.h"
 
 /* Do nothing; in many cases the default hook.  */
 
@@ -820,6 +824,19 @@ lhd_begin_section (const char *name)
 {
   section *section;
 
+  if (flag_bypass_asm)
+    {
+      static int initialized = false;
+      if (!initialized)
+	{
+	  gcc_assert (asm_out_file == NULL);
+          lto_set_current_out_file (lto_obj_file_open (asm_file_name, true));
+	  initialized = true;
+	}
+      lto_obj_begin_section (name);
+      return;
+    }
+
   /* Save the old section so we can restore it in lto_end_asm_section.  */
   gcc_assert (!saved_section);
   saved_section = in_section;
@@ -836,8 +853,13 @@ lhd_begin_section (const char *name)
    implementation just calls assemble_string.  */
 
 void
-lhd_append_data (const void *data, size_t len, void *)
+lhd_append_data (const void *data, size_t len, void *v)
 {
+  if (flag_bypass_asm)
+    {
+      lto_obj_append_data (data, len, v);
+      return;
+    }
   if (data)
     {
       timevar_push (TV_IPA_LTO_OUTPUT);
@@ -854,6 +876,11 @@ lhd_append_data (const void *data, size_t len, void *)
 void
 lhd_end_section (void)
 {
+  if (flag_bypass_asm)
+    {
+      lto_obj_end_section ();
+      return;
+    }
   if (saved_section)
     {
       switch_to_section (saved_section);
diff --git a/gcc/lto/lto-object.cc b/gcc/lto-object.cc
similarity index 94%
rename from gcc/lto/lto-object.cc
rename to gcc/lto-object.cc
index 329bbc71fd6..8ccc917a4eb 100644
--- a/gcc/lto/lto-object.cc
+++ b/gcc/lto-object.cc
@@ -21,9 +21,17 @@ along with GCC; see the file COPYING3.  If not see
 #include "config.h"
 #include "system.h"
 #include "coretypes.h"
-#include "tm.h"
+#include "tree.h"
+#include "basic-block.h"
+#include "tree-ssa-alias.h"
+#include "internal-fn.h"
+#include "gimple-expr.h"
+#include "is-a.h"
+#include "function.h"
+#include "gimple.h"
 #include "diagnostic-core.h"
-#include "lto.h"
+#include "tm.h"
+#include "lto-streamer.h"
 #include "lto-section-names.h"
 #include "simple-object.h"
 
@@ -133,7 +141,13 @@ lto_obj_file_open (const char *filename, bool writable)
     }
   else
     {
-      gcc_assert (saved_attributes != NULL);
+      if (!saved_attributes)
+        {
+          lto_file *tmp = lto_obj_file_open (flag_bypass_asm, false);
+          if (!tmp)
+            goto fail;
+          lto_obj_file_close (tmp);
+        }
       lo->sobj_w = simple_object_start_write (saved_attributes,
 					      LTO_SEGMENT_NAME,
 					      &errmsg, &err);
@@ -148,7 +162,8 @@ fail_errmsg:
     error ("%s: %s", fname, errmsg);
   else
     error ("%s: %s: %s", fname, errmsg, xstrerror (err));
-					 
+
+fail:
   if (lo->fd != -1)
     lto_obj_file_close ((lto_file *) lo);
   free (lo);
@@ -255,15 +270,15 @@ lto_obj_add_section (void *data, const char *name, off_t offset,
    the start and size of each section in the .o file.  */
 
 htab_t
-lto_obj_build_section_table (lto_file *lto_file, struct lto_section_list *list)
+lto_obj_build_section_table (lto_file *lto_file, struct lto_section_list *list,
+                             htab_t section_hash_table)
 {
   struct lto_simple_object *lo = (struct lto_simple_object *) lto_file;
-  htab_t section_hash_table;
+
   struct lto_obj_add_section_data loasd;
   const char *errmsg;
   int err;
 
-  section_hash_table = lto_obj_create_section_hash_table ();
 
   gcc_assert (lo->sobj_r != NULL && lo->sobj_w == NULL);
   loasd.section_hash_table = section_hash_table;
diff --git a/gcc/lto-streamer.h b/gcc/lto-streamer.h
index 597e9e405ec..4556583a6a8 100644
--- a/gcc/lto-streamer.h
+++ b/gcc/lto-streamer.h
@@ -759,6 +759,30 @@ public:
   lto_location_cache location_cache;
 };
 
+/* Hash table entry to hold the start offset and length of an LTO
+   section in a .o file.  */
+struct lto_section_slot
+{
+  const char *name;
+  intptr_t start;
+  size_t len;
+  struct lto_section_slot *next;
+};
+
+/* A list of section slots */
+struct lto_section_list
+{
+  struct lto_section_slot *first, *last;
+};
+
+/* A file.  */
+struct lto_file
+{
+  /* The name of the file.  */
+  const char *filename;
+  /* The offset for the object inside an ar archive file (or zero).  */
+  off_t offset;
+};
 
 /* In lto-section-in.cc  */
 extern class lto_input_block * lto_create_simple_input_block (
@@ -898,6 +922,17 @@ void lto_output_location_and_block (struct output_block *, struct bitpack_d *,
 void lto_output_init_mode_table (void);
 void lto_prepare_function_for_streaming (cgraph_node *);
 
+/* In lto-elf.c or lto-coff.c  */
+extern lto_file *lto_obj_file_open (const char *filename, bool writable);
+extern void lto_obj_file_close (lto_file *file);
+struct lto_section_list;
+extern htab_t lto_obj_build_section_table (lto_file *file, struct lto_section_list *list, htab_t section_hash_table);
+extern htab_t lto_obj_create_section_hash_table (void);
+extern void lto_obj_begin_section (const char *name);
+extern void lto_obj_append_data (const void *data, size_t len, void *block);
+extern void lto_obj_end_section (void);
+extern lto_file *lto_set_current_out_file (lto_file *file);
+extern lto_file *lto_get_current_out_file (void);
 
 /* In lto-cgraph.cc  */
 extern bool asm_nodes_output;
diff --git a/gcc/lto/Make-lang.in b/gcc/lto/Make-lang.in
index a2dcf0dfc12..41a822a317e 100644
--- a/gcc/lto/Make-lang.in
+++ b/gcc/lto/Make-lang.in
@@ -24,9 +24,9 @@ LTO_EXE = lto1$(exeext)
 LTO_DUMP_EXE = lto-dump$(exeext)
 LTO_DUMP_INSTALL_NAME := $(shell echo lto-dump|sed '$(program_transform_name)')
 # The LTO-specific object files inclued in $(LTO_EXE).
-LTO_OBJS = lto/lto-lang.o lto/lto.o lto/lto-object.o attribs.o lto/lto-partition.o lto/lto-symtab.o lto/lto-common.o
+LTO_OBJS = lto/lto-lang.o lto/lto.o attribs.o lto/lto-partition.o lto/lto-symtab.o lto/lto-common.o
 lto_OBJS = $(LTO_OBJS)
-LTO_DUMP_OBJS = lto/lto-lang.o lto/lto-object.o attribs.o lto/lto-partition.o lto/lto-symtab.o lto/lto-dump.o lto/lto-common.o
+LTO_DUMP_OBJS = lto/lto-lang.o attribs.o lto/lto-partition.o lto/lto-symtab.o lto/lto-dump.o lto/lto-common.o
 lto_dump_OBJS = $(LTO_DUMP_OBJS)
 
 # this is only useful in a LTO bootstrap, but this does not work right
diff --git a/gcc/lto/lto-common.cc b/gcc/lto/lto-common.cc
index ca28586a1e8..4a0c58cdbcd 100644
--- a/gcc/lto/lto-common.cc
+++ b/gcc/lto/lto-common.cc
@@ -2306,7 +2306,8 @@ lto_file_read (lto_file *file, FILE *resolution_file, int *count)
   struct lto_section_list section_list;
 
   memset (&section_list, 0, sizeof (struct lto_section_list));
-  section_hash_table = lto_obj_build_section_table (file, &section_list);
+  section_hash_table = lto_obj_create_section_hash_table ();
+  section_hash_table = lto_obj_build_section_table (file, &section_list, section_hash_table);
 
   /* Dump the details of LTO objects.  */
   if (flag_lto_dump_objects)
diff --git a/gcc/lto/lto-lang.cc b/gcc/lto/lto-lang.cc
index 8d58d924dff..64446fc9085 100644
--- a/gcc/lto/lto-lang.cc
+++ b/gcc/lto/lto-lang.cc
@@ -35,6 +35,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "lto-tree.h"
 #include "lto.h"
 #include "lto-common.h"
+#include "lto-streamer.h"
 #include "stringpool.h"
 #include "attribs.h"
 
diff --git a/gcc/lto/lto.h b/gcc/lto/lto.h
index 9f7fae95bc4..bb0a2852250 100644
--- a/gcc/lto/lto.h
+++ b/gcc/lto/lto.h
@@ -21,16 +21,6 @@ along with GCC; see the file COPYING3.  If not see
 #ifndef LTO_H
 #define LTO_H
 
-
-/* A file.  */
-struct lto_file
-{
-  /* The name of the file.  */
-  const char *filename;
-  /* The offset for the object inside an ar archive file (or zero).  */
-  off_t offset;
-};
-
 /* In lto-lang.cc  */
 extern const char *resolution_file_name;
 
@@ -39,36 +29,8 @@ extern tree lto_eh_personality (void);
 extern void lto_main (void);
 extern void lto_read_all_file_options (void);
 
-/* In lto-elf.c or lto-coff.c  */
-extern lto_file *lto_obj_file_open (const char *filename, bool writable);
-extern void lto_obj_file_close (lto_file *file);
-struct lto_section_list;
-extern htab_t lto_obj_build_section_table (lto_file *file, struct lto_section_list *list);
-extern htab_t lto_obj_create_section_hash_table (void);
-extern void lto_obj_begin_section (const char *name);
-extern void lto_obj_append_data (const void *data, size_t len, void *block);
-extern void lto_obj_end_section (void);
-extern lto_file *lto_set_current_out_file (lto_file *file);
-extern lto_file *lto_get_current_out_file (void);
-
 extern int lto_link_dump_id, decl_merge_dump_id, partition_dump_id;
 
-/* Hash table entry to hold the start offset and length of an LTO
-   section in a .o file.  */
-struct lto_section_slot
-{
-  const char *name;
-  intptr_t start;
-  size_t len;
-  struct lto_section_slot *next;
-};
-
-/* A list of section slots */
-struct lto_section_list
-{
-  struct lto_section_slot *first, *last;
-};
-
 extern unsigned int lto_option_lang_mask (void);
 
 #endif /* LTO_H */
diff --git a/gcc/toplev.cc b/gcc/toplev.cc
index ed546b2cad8..4464c5d6773 100644
--- a/gcc/toplev.cc
+++ b/gcc/toplev.cc
@@ -88,6 +88,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "ipa-modref.h"
 #include "ipa-param-manipulation.h"
 #include "dbgcnt.h"
+#include "lto-streamer.h"
 
 #if defined(DBX_DEBUGGING_INFO) || defined(XCOFF_DEBUGGING_INFO)
 #include "dbxout.h"
@@ -547,6 +548,12 @@ compile_file (void)
      even when user did not ask for it.  */
   if (flag_generate_lto && !flag_fat_lto_objects)
     {
+      if (flag_bypass_asm)
+        {
+          /* TODO  */
+        }
+      else
+        {
 #if defined ASM_OUTPUT_ALIGNED_DECL_COMMON
       ASM_OUTPUT_ALIGNED_DECL_COMMON (asm_out_file, NULL_TREE, "__gnu_lto_slim",
 				      HOST_WIDE_INT_1U, 8);
@@ -558,12 +565,13 @@ compile_file (void)
 			 HOST_WIDE_INT_1U,
 			 HOST_WIDE_INT_1U);
 #endif
+        }
     }
 
   /* Attach a special .ident directive to the end of the file to identify
      the version of GCC which compiled this code.  The format of the .ident
      string is patterned after the ones produced by native SVR4 compilers.  */
-  if (!flag_no_ident)
+  if (!flag_no_ident && !flag_bypass_asm)
     {
       const char *pkg_version = "(GNU) ";
       char *ident_str;
@@ -585,7 +593,11 @@ compile_file (void)
   /* This must be at the end.  Some target ports emit end of file directives
      into the assembly file here, and hence we cannot output anything to the
      assembly file after this point.  */
-  targetm.asm_out.file_end ();
+
+  if (flag_bypass_asm)
+    lto_obj_file_close (lto_get_current_out_file ());
+  else
+    targetm.asm_out.file_end ();
 
   timevar_stop (TV_PHASE_LATE_ASM);
 }
@@ -1861,7 +1873,8 @@ lang_dependent_init (const char *name)
 
   if (!flag_wpa)
     {
-      init_asm_output (name);
+      if (!flag_bypass_asm)
+        init_asm_output (name);
 
       if (!flag_generate_lto && !flag_compare_debug)
 	{
-- 
2.35.0

Re: Updating patch regarding bypassing assembler when generating LTO object files

[Iain Sandoe]

Hi Ankur,

> On 8 May 2022, at 15:29, Ankur Saini via Gcc <gcc@gcc.gnu.org> wrote:
> 

> I have been fiddling around with the patch regarding "bypassing assmebler
> while generating slim lto files" and managed to make it build with the
> current trunk. Though the patch seems to be working on Linux machine, it
> causes an ICE on macOS (it crashes in langhooks.cc while executing
> `lhd_begin_section ()`).

This is probably because Darwin (macOS) switches to a secondary output
when emitting LTO already, you will probably need to account for that in
the changes.

see gcc/config/darwin.cc: darwin_asm_lto_start() etc.

Iain

> 
> here is the patch ( not fully tested and is still a prototype ), I
> basically mimicked the entire previous patch (
> https://gcc.gnu.org/legacy-ml/gcc/2014-09/msg00340.html ) but on current
> source.
> 
> - Ankur
> 
> --- 
> 
> From e5d72a73962c34dcd818c17d440eb98ddd94e624 Mon Sep 17 00:00:00 2001
> From: Ankur Saini <arsenic@sourceware.org>
> Date: Sun, 8 May 2022 07:03:51 +0530
> Subject: [PATCH] bypass-asm prototype: 1
> 
> ---
> gcc/Makefile.in             |  1 +
> gcc/common.opt              |  3 +++
> gcc/langhooks.cc            | 29 +++++++++++++++++++++++++++-
> gcc/{lto => }/lto-object.cc | 29 +++++++++++++++++++++-------
> gcc/lto-streamer.h          | 35 ++++++++++++++++++++++++++++++++++
> gcc/lto/Make-lang.in        |  4 ++--
> gcc/lto/lto-common.cc       |  3 ++-
> gcc/lto/lto-lang.cc         |  1 +
> gcc/lto/lto.h               | 38 -------------------------------------
> gcc/toplev.cc               | 19 ++++++++++++++++---
> 10 files changed, 110 insertions(+), 52 deletions(-)
> rename gcc/{lto => }/lto-object.cc (94%)
> 
> diff --git a/gcc/Makefile.in b/gcc/Makefile.in
> index 31ff95500c9..3d1241d5819 100644
> --- a/gcc/Makefile.in
> +++ b/gcc/Makefile.in
> @@ -1509,6 +1509,7 @@ OBJS = \
> 	lto-section-out.o \
> 	lto-opts.o \
> 	lto-compress.o \
> +	lto-object.o \
> 	mcf.o \
> 	mode-switching.o \
> 	modulo-sched.o \
> diff --git a/gcc/common.opt b/gcc/common.opt
> index 8a0dafc522d..6348197380d 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -1158,6 +1158,9 @@ fbtr-bb-exclusive
> Common Ignore
> Does nothing.  Preserved for backward compatibility.
> 
> +fbypass-asm=
> +Common Joined Var(flag_bypass_asm)
> +
> fcallgraph-info
> Common RejectNegative Var(flag_callgraph_info) Init(NO_CALLGRAPH_INFO);
> Output callgraph information on a per-file basis.
> diff --git a/gcc/langhooks.cc b/gcc/langhooks.cc
> index df970678a08..abfab7a27e0 100644
> --- a/gcc/langhooks.cc
> +++ b/gcc/langhooks.cc
> @@ -38,6 +38,10 @@ along with GCC; see the file COPYING3.  If not see
> #include "stor-layout.h"
> #include "cgraph.h"
> #include "debug.h"
> +#include "function.h"
> +#include "basic-block.h"
> +#include "gimple.h"
> +#include "lto-streamer.h"
> 
> /* Do nothing; in many cases the default hook.  */
> 
> @@ -820,6 +824,19 @@ lhd_begin_section (const char *name)
> {
>   section *section;
> 
> +  if (flag_bypass_asm)
> +    {
> +      static int initialized = false;
> +      if (!initialized)
> +	{
> +	  gcc_assert (asm_out_file == NULL);
> +          lto_set_current_out_file (lto_obj_file_open (asm_file_name, true));
> +	  initialized = true;
> +	}
> +      lto_obj_begin_section (name);
> +      return;
> +    }
> +
>   /* Save the old section so we can restore it in lto_end_asm_section.  */
>   gcc_assert (!saved_section);
>   saved_section = in_section;
> @@ -836,8 +853,13 @@ lhd_begin_section (const char *name)
>    implementation just calls assemble_string.  */
> 
> void
> -lhd_append_data (const void *data, size_t len, void *)
> +lhd_append_data (const void *data, size_t len, void *v)
> {
> +  if (flag_bypass_asm)
> +    {
> +      lto_obj_append_data (data, len, v);
> +      return;
> +    }
>   if (data)
>     {
>       timevar_push (TV_IPA_LTO_OUTPUT);
> @@ -854,6 +876,11 @@ lhd_append_data (const void *data, size_t len, void *)
> void
> lhd_end_section (void)
> {
> +  if (flag_bypass_asm)
> +    {
> +      lto_obj_end_section ();
> +      return;
> +    }
>   if (saved_section)
>     {
>       switch_to_section (saved_section);
> diff --git a/gcc/lto/lto-object.cc b/gcc/lto-object.cc
> similarity index 94%
> rename from gcc/lto/lto-object.cc
> rename to gcc/lto-object.cc
> index 329bbc71fd6..8ccc917a4eb 100644
> --- a/gcc/lto/lto-object.cc
> +++ b/gcc/lto-object.cc
> @@ -21,9 +21,17 @@ along with GCC; see the file COPYING3.  If not see
> #include "config.h"
> #include "system.h"
> #include "coretypes.h"
> -#include "tm.h"
> +#include "tree.h"
> +#include "basic-block.h"
> +#include "tree-ssa-alias.h"
> +#include "internal-fn.h"
> +#include "gimple-expr.h"
> +#include "is-a.h"
> +#include "function.h"
> +#include "gimple.h"
> #include "diagnostic-core.h"
> -#include "lto.h"
> +#include "tm.h"
> +#include "lto-streamer.h"
> #include "lto-section-names.h"
> #include "simple-object.h"
> 
> @@ -133,7 +141,13 @@ lto_obj_file_open (const char *filename, bool writable)
>     }
>   else
>     {
> -      gcc_assert (saved_attributes != NULL);
> +      if (!saved_attributes)
> +        {
> +          lto_file *tmp = lto_obj_file_open (flag_bypass_asm, false);
> +          if (!tmp)
> +            goto fail;
> +          lto_obj_file_close (tmp);
> +        }
>       lo->sobj_w = simple_object_start_write (saved_attributes,
> 					      LTO_SEGMENT_NAME,
> 					      &errmsg, &err);
> @@ -148,7 +162,8 @@ fail_errmsg:
>     error ("%s: %s", fname, errmsg);
>   else
>     error ("%s: %s: %s", fname, errmsg, xstrerror (err));
> -					 
> +
> +fail:
>   if (lo->fd != -1)
>     lto_obj_file_close ((lto_file *) lo);
>   free (lo);
> @@ -255,15 +270,15 @@ lto_obj_add_section (void *data, const char *name, off_t offset,
>    the start and size of each section in the .o file.  */
> 
> htab_t
> -lto_obj_build_section_table (lto_file *lto_file, struct lto_section_list *list)
> +lto_obj_build_section_table (lto_file *lto_file, struct lto_section_list *list,
> +                             htab_t section_hash_table)
> {
>   struct lto_simple_object *lo = (struct lto_simple_object *) lto_file;
> -  htab_t section_hash_table;
> +
>   struct lto_obj_add_section_data loasd;
>   const char *errmsg;
>   int err;
> 
> -  section_hash_table = lto_obj_create_section_hash_table ();
> 
>   gcc_assert (lo->sobj_r != NULL && lo->sobj_w == NULL);
>   loasd.section_hash_table = section_hash_table;
> diff --git a/gcc/lto-streamer.h b/gcc/lto-streamer.h
> index 597e9e405ec..4556583a6a8 100644
> --- a/gcc/lto-streamer.h
> +++ b/gcc/lto-streamer.h
> @@ -759,6 +759,30 @@ public:
>   lto_location_cache location_cache;
> };
> 
> +/* Hash table entry to hold the start offset and length of an LTO
> +   section in a .o file.  */
> +struct lto_section_slot
> +{
> +  const char *name;
> +  intptr_t start;
> +  size_t len;
> +  struct lto_section_slot *next;
> +};
> +
> +/* A list of section slots */
> +struct lto_section_list
> +{
> +  struct lto_section_slot *first, *last;
> +};
> +
> +/* A file.  */
> +struct lto_file
> +{
> +  /* The name of the file.  */
> +  const char *filename;
> +  /* The offset for the object inside an ar archive file (or zero).  */
> +  off_t offset;
> +};
> 
> /* In lto-section-in.cc  */
> extern class lto_input_block * lto_create_simple_input_block (
> @@ -898,6 +922,17 @@ void lto_output_location_and_block (struct output_block *, struct bitpack_d *,
> void lto_output_init_mode_table (void);
> void lto_prepare_function_for_streaming (cgraph_node *);
> 
> +/* In lto-elf.c or lto-coff.c  */
> +extern lto_file *lto_obj_file_open (const char *filename, bool writable);
> +extern void lto_obj_file_close (lto_file *file);
> +struct lto_section_list;
> +extern htab_t lto_obj_build_section_table (lto_file *file, struct lto_section_list *list, htab_t section_hash_table);
> +extern htab_t lto_obj_create_section_hash_table (void);
> +extern void lto_obj_begin_section (const char *name);
> +extern void lto_obj_append_data (const void *data, size_t len, void *block);
> +extern void lto_obj_end_section (void);
> +extern lto_file *lto_set_current_out_file (lto_file *file);
> +extern lto_file *lto_get_current_out_file (void);
> 
> /* In lto-cgraph.cc  */
> extern bool asm_nodes_output;
> diff --git a/gcc/lto/Make-lang.in b/gcc/lto/Make-lang.in
> index a2dcf0dfc12..41a822a317e 100644
> --- a/gcc/lto/Make-lang.in
> +++ b/gcc/lto/Make-lang.in
> @@ -24,9 +24,9 @@ LTO_EXE = lto1$(exeext)
> LTO_DUMP_EXE = lto-dump$(exeext)
> LTO_DUMP_INSTALL_NAME := $(shell echo lto-dump|sed '$(program_transform_name)')
> # The LTO-specific object files inclued in $(LTO_EXE).
> -LTO_OBJS = lto/lto-lang.o lto/lto.o lto/lto-object.o attribs.o lto/lto-partition.o lto/lto-symtab.o lto/lto-common.o
> +LTO_OBJS = lto/lto-lang.o lto/lto.o attribs.o lto/lto-partition.o lto/lto-symtab.o lto/lto-common.o
> lto_OBJS = $(LTO_OBJS)
> -LTO_DUMP_OBJS = lto/lto-lang.o lto/lto-object.o attribs.o lto/lto-partition.o lto/lto-symtab.o lto/lto-dump.o lto/lto-common.o
> +LTO_DUMP_OBJS = lto/lto-lang.o attribs.o lto/lto-partition.o lto/lto-symtab.o lto/lto-dump.o lto/lto-common.o
> lto_dump_OBJS = $(LTO_DUMP_OBJS)
> 
> # this is only useful in a LTO bootstrap, but this does not work right
> diff --git a/gcc/lto/lto-common.cc b/gcc/lto/lto-common.cc
> index ca28586a1e8..4a0c58cdbcd 100644
> --- a/gcc/lto/lto-common.cc
> +++ b/gcc/lto/lto-common.cc
> @@ -2306,7 +2306,8 @@ lto_file_read (lto_file *file, FILE *resolution_file, int *count)
>   struct lto_section_list section_list;
> 
>   memset (&section_list, 0, sizeof (struct lto_section_list));
> -  section_hash_table = lto_obj_build_section_table (file, &section_list);
> +  section_hash_table = lto_obj_create_section_hash_table ();
> +  section_hash_table = lto_obj_build_section_table (file, &section_list, section_hash_table);
> 
>   /* Dump the details of LTO objects.  */
>   if (flag_lto_dump_objects)
> diff --git a/gcc/lto/lto-lang.cc b/gcc/lto/lto-lang.cc
> index 8d58d924dff..64446fc9085 100644
> --- a/gcc/lto/lto-lang.cc
> +++ b/gcc/lto/lto-lang.cc
> @@ -35,6 +35,7 @@ along with GCC; see the file COPYING3.  If not see
> #include "lto-tree.h"
> #include "lto.h"
> #include "lto-common.h"
> +#include "lto-streamer.h"
> #include "stringpool.h"
> #include "attribs.h"
> 
> diff --git a/gcc/lto/lto.h b/gcc/lto/lto.h
> index 9f7fae95bc4..bb0a2852250 100644
> --- a/gcc/lto/lto.h
> +++ b/gcc/lto/lto.h
> @@ -21,16 +21,6 @@ along with GCC; see the file COPYING3.  If not see
> #ifndef LTO_H
> #define LTO_H
> 
> -
> -/* A file.  */
> -struct lto_file
> -{
> -  /* The name of the file.  */
> -  const char *filename;
> -  /* The offset for the object inside an ar archive file (or zero).  */
> -  off_t offset;
> -};
> -
> /* In lto-lang.cc  */
> extern const char *resolution_file_name;
> 
> @@ -39,36 +29,8 @@ extern tree lto_eh_personality (void);
> extern void lto_main (void);
> extern void lto_read_all_file_options (void);
> 
> -/* In lto-elf.c or lto-coff.c  */
> -extern lto_file *lto_obj_file_open (const char *filename, bool writable);
> -extern void lto_obj_file_close (lto_file *file);
> -struct lto_section_list;
> -extern htab_t lto_obj_build_section_table (lto_file *file, struct lto_section_list *list);
> -extern htab_t lto_obj_create_section_hash_table (void);
> -extern void lto_obj_begin_section (const char *name);
> -extern void lto_obj_append_data (const void *data, size_t len, void *block);
> -extern void lto_obj_end_section (void);
> -extern lto_file *lto_set_current_out_file (lto_file *file);
> -extern lto_file *lto_get_current_out_file (void);
> -
> extern int lto_link_dump_id, decl_merge_dump_id, partition_dump_id;
> 
> -/* Hash table entry to hold the start offset and length of an LTO
> -   section in a .o file.  */
> -struct lto_section_slot
> -{
> -  const char *name;
> -  intptr_t start;
> -  size_t len;
> -  struct lto_section_slot *next;
> -};
> -
> -/* A list of section slots */
> -struct lto_section_list
> -{
> -  struct lto_section_slot *first, *last;
> -};
> -
> extern unsigned int lto_option_lang_mask (void);
> 
> #endif /* LTO_H */
> diff --git a/gcc/toplev.cc b/gcc/toplev.cc
> index ed546b2cad8..4464c5d6773 100644
> --- a/gcc/toplev.cc
> +++ b/gcc/toplev.cc
> @@ -88,6 +88,7 @@ along with GCC; see the file COPYING3.  If not see
> #include "ipa-modref.h"
> #include "ipa-param-manipulation.h"
> #include "dbgcnt.h"
> +#include "lto-streamer.h"
> 
> #if defined(DBX_DEBUGGING_INFO) || defined(XCOFF_DEBUGGING_INFO)
> #include "dbxout.h"
> @@ -547,6 +548,12 @@ compile_file (void)
>      even when user did not ask for it.  */
>   if (flag_generate_lto && !flag_fat_lto_objects)
>     {
> +      if (flag_bypass_asm)
> +        {
> +          /* TODO  */
> +        }
> +      else
> +        {
> #if defined ASM_OUTPUT_ALIGNED_DECL_COMMON
>       ASM_OUTPUT_ALIGNED_DECL_COMMON (asm_out_file, NULL_TREE, "__gnu_lto_slim",
> 				      HOST_WIDE_INT_1U, 8);
> @@ -558,12 +565,13 @@ compile_file (void)
> 			 HOST_WIDE_INT_1U,
> 			 HOST_WIDE_INT_1U);
> #endif
> +        }
>     }
> 
>   /* Attach a special .ident directive to the end of the file to identify
>      the version of GCC which compiled this code.  The format of the .ident
>      string is patterned after the ones produced by native SVR4 compilers.  */
> -  if (!flag_no_ident)
> +  if (!flag_no_ident && !flag_bypass_asm)
>     {
>       const char *pkg_version = "(GNU) ";
>       char *ident_str;
> @@ -585,7 +593,11 @@ compile_file (void)
>   /* This must be at the end.  Some target ports emit end of file directives
>      into the assembly file here, and hence we cannot output anything to the
>      assembly file after this point.  */
> -  targetm.asm_out.file_end ();
> +
> +  if (flag_bypass_asm)
> +    lto_obj_file_close (lto_get_current_out_file ());
> +  else
> +    targetm.asm_out.file_end ();
> 
>   timevar_stop (TV_PHASE_LATE_ASM);
> }
> @@ -1861,7 +1873,8 @@ lang_dependent_init (const char *name)
> 
>   if (!flag_wpa)
>     {
> -      init_asm_output (name);
> +      if (!flag_bypass_asm)
> +        init_asm_output (name);
> 
>       if (!flag_generate_lto && !flag_compare_debug)
> 	{
> -- 
> 2.35.0
> 
>