lto: Bypass assembler when generating LTO object files.

    This patch applies Jan Hubicka previous patch on current sources.
    Now compiler is able to produce object files without assembler although
    a lot of things are missing such as __lto_slim symbol, debug symbols
    etc. They will be added in future patches. To test this current patch,
    use these command below.
    1) ./xgcc -B ./ -O3 a.c -flto -S -fbypass-asm=crtbegin.o  -o a.o
    2) ./xgcc -B ./ -O2 a.o -flto
    3)  ./a.out

    We are currntly working with elf-only support (mach-o, coff, xcoff etc
    will be dealt later) so this will only work on a linux machine. I have tested
    this on my machine ( Arch linux, Machine: Advanced Micro Devices X86-64) and
    all LTO test cases passed as expected.

    gcc/ChangeLog:

            * Makefile.in:
            * common.opt:
            * langhooks.cc (lhd_begin_section):
            (lhd_append_data):
            (lhd_end_section):
            * lto/lto-object.cc: Moved to...
            * lto-object.cc: ...here.
            * lto-streamer.h (struct lto_section_slot):
            (struct lto_section_list):
            (struct lto_file):
            (lto_obj_file_open):
            (lto_obj_file_close):
            (lto_obj_build_section_table):
            (lto_obj_create_section_hash_table):
            (lto_obj_begin_section):
            (lto_obj_append_data):
            (lto_obj_end_section):
            (lto_set_current_out_file):
            (lto_get_current_out_file):
            * toplev.cc (compile_file):
            (lang_dependent_init):

    gcc/lto/ChangeLog:

            * Make-lang.in:
            * lto-common.cc (lto_file_read):
            * lto-lang.cc:
            * lto.h (struct lto_file):
            (lto_obj_file_open):
            (lto_obj_file_close):
            (struct lto_section_list):
            (lto_obj_build_section_table):
            (lto_obj_create_section_hash_table):
            (lto_obj_begin_section):
            (lto_obj_append_data):
            (lto_obj_end_section):
            (lto_set_current_out_file):
            (lto_get_current_out_file):
            (struct lto_section_slot):

Signed-off-by: Rishi Raj <rishiraj45035@gmail.com>

10 files changed, 110 insertions, 52 deletions

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index c478ec8..c9ae222 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1560,6 +1560,7 @@ 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 25f650e..ba7a18e 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1169,6 +1169,9 @@ 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 9a1a9ec..a76ed97 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.  */
 
@@ -817,6 +821,19 @@ 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;
@@ -833,8 +850,13 @@ 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);
@@ -851,6 +873,11 @@ 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
index 965d31e..cb1c3a6 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 0556b34..0c8e5d6 100644
--- a/gcc/lto-streamer.h
+++ b/gcc/lto-streamer.h
@@ -764,6 +764,30 @@ 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 (
@@ -903,6 +927,17 @@ 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 98aa9f4..70144ce 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 703e665..1ec488a 100644
--- a/gcc/lto/lto-common.cc
+++ b/gcc/lto/lto-common.cc
@@ -2326,7 +2326,8 @@ 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 14d419c..cf33bf1 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 810d662..4c3c84b 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 6c1a6f4..fec4163 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"
 
 #include "selftest.h"
 
@@ -539,6 +540,12 @@ 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);
@@ -550,12 +557,13 @@ 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;
@@ -577,7 +585,11 @@ 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);
 }
@@ -1819,7 +1831,8 @@ 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)
 	{