[PATCH] LTO: get_section: add new argument

[Martin Liška]

Hey.

During partial linking we ipa_prop_write_jump_functions twice from 2 IPA
pass (fnsummary and cp). That produces 2 compressed blocks in an ELF section
and then zstd complains as sections size does not correspond to the compressed
stream.

I'm adding both sanity check changes and the fix in ipa-prop.c.
I guess Martin and Honza can explain it in more detail?

Patch can bootstrap on x86_64-linux-gnu and survives regression tests.

Ready to be installed?
Thanks,
Martin

gcc/ChangeLog:

	PR lto/97508
	* langhooks.c (lhd_begin_section): Call get_section with
	not_existing = true.
	* output.h (get_section): Add new argument.
	* varasm.c (get_section): Fail when NOT_EXISTING is true
	and a section already exists.
	* ipa-prop.c (ipa_prop_write_jump_functions): Do not stream
	twice.
---
  gcc/ipa-prop.c  |  9 +++++++++
  gcc/langhooks.c |  2 +-
  gcc/output.h    |  3 ++-
  gcc/varasm.c    | 12 ++++++++++--
  4 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/gcc/ipa-prop.c b/gcc/ipa-prop.c
index a848f1db95e..d43fd2eee4f 100644
--- a/gcc/ipa-prop.c
+++ b/gcc/ipa-prop.c
@@ -5067,6 +5067,13 @@ ipa_prop_write_jump_functions (void)
    lto_symtab_encoder_iterator lsei;
    lto_symtab_encoder_t encoder;
  
+  /* The function can be called from 2 IPA_PASSES: "fnsummary" and "cp"
+     which happens in partial linking (-r).  Prevent double streaming
+     as reported in PR97508.  */
+  static bool already_stremed = false;
+  if (already_stremed)
+    return;
+
    if (!ipa_node_params_sum || !ipa_edge_args_sum)
      return;
  
@@ -5096,6 +5103,8 @@ ipa_prop_write_jump_functions (void)
    streamer_write_char_stream (ob->main_stream, 0);
    produce_asm (ob, NULL);
    destroy_output_block (ob);
+
+  already_stremed = true;
  }
  
  /* Read section in file FILE_DATA of length LEN with data DATA.  */
diff --git a/gcc/langhooks.c b/gcc/langhooks.c
index 8819a8859d4..d82f54251fd 100644
--- a/gcc/langhooks.c
+++ b/gcc/langhooks.c
@@ -790,7 +790,7 @@ lhd_begin_section (const char *name)
      saved_section = text_section;
  
    /* Create a new section and switch to it.  */
-  section = get_section (name, SECTION_DEBUG | SECTION_EXCLUDE, NULL);
+  section = get_section (name, SECTION_DEBUG | SECTION_EXCLUDE, NULL, true);
    switch_to_section (section);
  }
  
diff --git a/gcc/output.h b/gcc/output.h
index eb253c50329..2f2f1697fd8 100644
--- a/gcc/output.h
+++ b/gcc/output.h
@@ -523,7 +523,8 @@ extern GTY(()) bool in_cold_section_p;
  
  extern section *get_unnamed_section (unsigned int, void (*) (const void *),
  				     const void *);
-extern section *get_section (const char *, unsigned int, tree);
+extern section *get_section (const char *, unsigned int, tree,
+			     bool not_existing = false);
  extern section *get_named_section (tree, const char *, int);
  extern section *get_variable_section (tree, bool);
  extern void place_block_symbol (rtx);
diff --git a/gcc/varasm.c b/gcc/varasm.c
index ea0b59cf44a..207c9b077d1 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -277,10 +277,12 @@ get_noswitch_section (unsigned int flags, noswitch_section_callback callback)
  }
  
  /* Return the named section structure associated with NAME.  Create
-   a new section with the given fields if no such structure exists.  */
+   a new section with the given fields if no such structure exists.
+   When NOT_EXISTING, then fail if the section already exists.  */
  
  section *
-get_section (const char *name, unsigned int flags, tree decl)
+get_section (const char *name, unsigned int flags, tree decl,
+	     bool not_existing)
  {
    section *sect, **slot;
  
@@ -297,6 +299,12 @@ get_section (const char *name, unsigned int flags, tree decl)
      }
    else
      {
+      if (not_existing)
+	{
+	  error ("Section already exists: %qs", name);
+	  gcc_unreachable ();
+	}
+
        sect = *slot;
        /* It is fine if one of the sections has SECTION_NOTYPE as long as
           the other has none of the contrary flags (see the logic at the end
-- 
2.28.0