This is a slightly revised version of the WIP patch against GCC 5.1 I
previously posted here:
https://gcc.gnu.org/ml/gcc/2016-05/msg00135.html
To recap, I needed a biarch x86_64 mingw-w64 target compiler that uses
DWARF-2 exception handling in 32-bit mode (for compatibility with an
older i686-mingw32 toolchain configured with --disable-sjlj-exceptions).
But, the configuration machinery was rejecting this. It used to be
that SJLJ exceptions were the only choice for 64-bit mode so it was
correct to reject --disable-sjlj-exceptions in a biarch toolchain, but
now the default for 64-bit mode is SEH instead. With this patch,
configuring with --disable-sjlj-exceptions selects DWARF-2 EH in 32-bit
mode and SEH in 64-bit mode.
I tested this in a cross-compiler configured to build C and C++ only for
x86_64 mingw-w64 target, and test results look about the same as the
default configuration, which uses SJLJ for 32-bit mode. (If it's
relevant, I also used the compiler built with the 5.1 version of the
patch to build complete Windows-host toolchains for nios2-elf and
nios2-linux-gnu, which I tested by running the GDB testsuite.) There
are no actual code changes here so I'd expect the 32-bit DWARF-2 EH
support to work exactly the same as in a 32-bit-only x86 configuration.
OK to commit?
-Sandra
2016-05-19 Sandra Loosemore <san...@codesourcery.com>
gcc/
* config/i386/cygming.h (DWARF2_UNWIND_INFO): Allow
--disable-sjlj-exceptions for TARGET_BI_ARCH to select DWARF-2 EH
for 32-bit mode and SEH for 64-bit.
* config/i386/mingw32.h (SHARED_LIBGCC_UNDEFS_SPEC): Handle
TARGET_64BIT_DEFAULT.
libgcc/
* config.host [x86_64-*-cygwin*]: Handle tmake_eh_file for mixed
dw2/seh configuration.
[x86_64-*-mingw*]: Likewise.
Index: gcc/config/i386/cygming.h
===================================================================
--- gcc/config/i386/cygming.h (revision 236256)
+++ gcc/config/i386/cygming.h (working copy)
@@ -339,16 +339,13 @@ do { \
#define ASM_COMMENT_START " #"
#ifndef DWARF2_UNWIND_INFO
-/* If configured with --disable-sjlj-exceptions, use DWARF2, else
- default to SJLJ. */
+/* If configured with --disable-sjlj-exceptions, use DWARF2 for 32-bit
+ mode else default to SJLJ. 64-bit code uses SEH unless you request
+ SJLJ. */
#if (defined (CONFIG_SJLJ_EXCEPTIONS) && !CONFIG_SJLJ_EXCEPTIONS)
/* The logic of this #if must be kept synchronised with the logic
- for selecting the tmake_eh_file fragment in config.gcc. */
+ for selecting the tmake_eh_file fragment in libgcc/config.host. */
#define DWARF2_UNWIND_INFO 1
-/* If multilib is selected break build as sjlj is required. */
-#if defined (TARGET_BI_ARCH)
-#error For 64-bit windows and 32-bit based multilib version of gcc just SJLJ exceptions are supported.
-#endif
#else
#define DWARF2_UNWIND_INFO 0
#endif
Index: gcc/config/i386/mingw32.h
===================================================================
--- gcc/config/i386/mingw32.h (revision 236256)
+++ gcc/config/i386/mingw32.h (working copy)
@@ -100,10 +100,12 @@ along with GCC; see the file COPYING3.
#if DWARF2_UNWIND_INFO
/* DW2-unwind is just available for 32-bit mode. */
#if TARGET_64BIT_DEFAULT
-#error DW2 unwind is not available for 64-bit.
-#endif
+#define SHARED_LIBGCC_UNDEFS_SPEC \
+ "%{m32: %{shared-libgcc: -u ___register_frame_info -u ___deregister_frame_info}}"
+#else
#define SHARED_LIBGCC_UNDEFS_SPEC \
"%{shared-libgcc: -u ___register_frame_info -u ___deregister_frame_info}"
+#endif
#else
#define SHARED_LIBGCC_UNDEFS_SPEC ""
#endif
Index: libgcc/config.host
===================================================================
--- libgcc/config.host (revision 236256)
+++ libgcc/config.host (working copy)
@@ -678,6 +678,9 @@ x86_64-*-cygwin*)
# This has to match the logic for DWARF2_UNWIND_INFO in gcc/config/i386/cygming.h
if test x$ac_cv_sjlj_exceptions = xyes; then
tmake_eh_file="i386/t-sjlj-eh"
+ elif test "${host_address}" = 32; then
+ # biarch -m32 with --disable-sjlj-exceptions
+ tmake_eh_file="i386/t-dw2-eh"
else
tmake_eh_file="i386/t-seh-eh"
fi
@@ -730,6 +733,10 @@ x86_64-*-mingw*)
# This has to match the logic for DWARF2_UNWIND_INFO in gcc/config/i386/cygming.h
if test x$ac_cv_sjlj_exceptions = xyes; then
tmake_eh_file="i386/t-sjlj-eh"
+ elif test "${host_address}" = 32; then
+ # biarch -m32 with --disable-sjlj-exceptions
+ tmake_eh_file="i386/t-dw2-eh"
+ md_unwind_header=i386/w32-unwind.h
else
tmake_eh_file="i386/t-seh-eh"
fi
