Speed up direct linking with DLLs on Windows (1/2).

This patch deals with the auto-import feature.  There are 2 versions
of this feature: the original one, which was piggybacked on the OS
loader with an optional help from the runtime (--enable-auto-import
--enable-runtime-pseudo-reloc-v1) and is still the one mostly
documented in the sources and manual; the enhanced one by Kai Tietz,
which is entirely piggybacked on the runtime (--enable-auto-import
--enable-runtime-pseudo-reloc-v2) and is the default for Mingw and
Cygwin nowadays.

The implementation is inefficient because of pe[p]_find_data_imports:
for every undefined symbol, the function walks the entire set of
relocations for all the input files and does a direct name comparison
for each of them.

This is easily fixable by using a hash-based map for v1 and a simple
hash table for v2.  This patch leaves v1 alone and only changes v2.
It also factors out pe[p]_find_data_imports into a common function,
removes old cruft left and right, and attempts to better separate
the implementations of v1 and v2 in the code.

ld/
	* emultempl/pe.em (U_SIZE): Delete.
	(pe_data_import_dll): Likewise.
	(make_import_fixup): Return void, take 4th parameter and pass it down
	in call to pe_create_import_fixup.
	(pe_find_data_imports): Move to...
	(gld_${EMULATION_NAME}_after_open): Run the stdcall fixup pass after
	the auto-import pass and add a guard before running the latter.
	* emultempl/pep.em (U_SIZE): Delete.
	(pep_data_import_dll): Likewise.
	(make_import_fixup): Return void, take 4th parameter and pass it down
	in call to pe_create_import_fixup.
	(pep_find_data_imports): Move to...
	(gld_${EMULATION_NAME}_after_open): Run the stdcall fixup pass after
	the auto-import pass and add a guard before running the latter.
	* pe-dll.c (runtime_pseudp_reloc_v2_init): Change type to bfd_boolean.
	(pe_walk_relocs_of_symbol): Rename into...
	(pe_walk_relocs): ...this.  Add 2 more parameters,4th parameter to the
	callback prototype and pass 4th parameter in calls to the callback.
	If the import hash table is present, invoke the callback on the reloc
	if the symbol name is in the table.
	(pe_find_data_imports): ...here.  Take 2 parameters.  Build an import
	hash table for the pseudo-relocation support version 2.  When it is
	built, walk the relocations only once at the end; when it is not, do
	not build a fixup when the symbol isn't part of an import table.
	Issue the associated warning only after a first fixup is built.
	(tmp_seq2): Delete.
	(make_singleton_name_imp): Likewise.
	(make_import_fixup_mark): Return const char * and a stable string.
	(make_import_fixup_entry): Do not deal with the pseudo-relocation
	support version 2.
	(make_runtime_pseudo_reloc): Factor out code and fix formatting.
	(pe_create_import_fixup): Add 5th parameter.  Clearly separate the
	pseudo-relocation support version 2 from the rest.  Fix formatting.
	* pe-dll.h (pe_walk_relocs_of_symbol): Delete.
	(pe_find_data_imports): Declare.
	(pe_create_import_fixup): Add 5th parameter.
	* pep-dll.c (pe_data_import_dll): Delete.
	(pe_find_data_imports): Define.
	(pe_walk_relocs_of_symbol): Delete.
	* pep-dll.h (pep_walk_relocs_of_symbol): Delete.
	(pep_find_data_imports): Declare.
	(pep_create_import_fixup): Add 5th parameter.
	* ld.texinfo (--enable-auto-import): Adjust to new implementation.

1 files changed, 11 insertions, 8 deletions

diff --git a/ld/ld.texinfo b/ld/ld.texinfo
index 391f52b..9425c65 100644
--- a/ld/ld.texinfo
+++ b/ld/ld.texinfo
@@ -2752,11 +2752,16 @@ uwin, pw, etc.  For instance, cygwin DLLs typically use
 @kindex --enable-auto-import
 @item --enable-auto-import
 Do sophisticated linking of @code{_symbol} to @code{__imp__symbol} for
-DATA imports from DLLs, and create the necessary thunking symbols when
-building the import libraries with those DATA exports. Note: Use of the
-'auto-import' extension will cause the text section of the image file
-to be made writable. This does not conform to the PE-COFF format
-specification published by Microsoft.
+DATA imports from DLLs, thus making it possible to bypass the dllimport
+mechanism on the user side and to reference unmangled symbol names.
+[This option is specific to the i386 PE targeted port of the linker]
+
+The following remarks pertain to the original implementation of the
+feature and are obsolete nowadays for Cygwin and MinGW targets.
+
+Note: Use of the 'auto-import' extension will cause the text section
+of the image file to be made writable. This does not conform to the
+PE-COFF format specification published by Microsoft.
 
 Note - use of the 'auto-import' extension will also cause read only
 data which would normally be placed into the .rdata section to be
@@ -2878,7 +2883,6 @@ A fourth way to avoid this problem is to re-code your
 library to use a functional interface rather than a data interface
 for the offending variables (e.g. set_foo() and get_foo() accessor
 functions).
-[This option is specific to the i386 PE targeted port of the linker]
 
 @kindex --disable-auto-import
 @item --disable-auto-import
@@ -2896,8 +2900,7 @@ environment to adjust references to such data in your client code.
 
 @kindex --disable-runtime-pseudo-reloc
 @item --disable-runtime-pseudo-reloc
-Do not create pseudo relocations for non-zero offset DATA imports from
-DLLs.
+Do not create pseudo relocations for non-zero offset DATA imports from DLLs.
 [This option is specific to the i386 PE targeted port of the linker]
 
 @kindex --enable-extra-pe-debug