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PowerPC: PR libgcc/97543 and libgcc/97643, fix long double issues

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If you use a compiler with long double defaulting to 64-bit instead of 128-bit
with IBM extended double, you get linker warnings about mis-matches in the gnu
attributes for long double (PR libgcc/97543).  Even if the compiler is
configured to have long double be 64 bit as the default with the configuration
option '--without-long-double-128' you get the warnings.

You also get the same issues if you use a compiler with long double defaulting
to IEEE 128-bit instead of IBM extended double (PR libgcc/97643).

The issue is the way libgcc.a/libgcc.so is built.  Right now when building
libgcc under Linux, the long double size is set to 128-bits when building
libgcc.  However, the gnu attributes are set, leading to the warnings.

One feature of the current GNU attribute implementation is if you have a shared
library (such as libgcc_s.so), the GNU attributes for the shared library is an
inclusive OR of all of the objects within the library.  This means if any
object file that uses the -mlong-double-128 option and uses long double, the GNU
attributes for the library will indicate that it uses 128-bit IBM long
doubles.  If you have a static library, you will get the warning only if you
actually reference an object file  with the attribute set.

This patch does two things:

    1)	All of the object files that support IBM 128-bit long doubles
	explicitly set the ABI to IBM extended double.

    2)	I turned off GNU attributes for building the shared library or for
        building the IBM 128-bit long double support.

libgcc/
2020-12-03  Michael Meissner  <meissner@linux.ibm.com>

	PR libgcc/97543
	PR libgcc/97643
	* config/rs6000/t-linux (IBM128_STATIC_OBJS): New make variable.
	(IBM128_SHARED_OBJS): New make variable.
	(IBM128_OBJS): New make variable.  Set all objects to use the
	explicit IBM format, and disable gnu attributes.
	(IBM128_CFLAGS): New make variable.
	(gcc_s_compile): Add -mno-gnu-attribute to all shared library
	modules.
This commit is contained in:
Michael Meissner 2020-12-03 14:50:26 -05:00
parent 30b606bb9b
commit 9f1a650199
1 changed files with 22 additions and 0 deletions
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22
libgcc/config/rs6000/t-linux
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@ -6,3 +6,25 @@ HOST_LIBGCC2_CFLAGS += -mlong-double-128
# smaller and faster libgcc code. Directly specifying -mcmodel=small
# would need to take into account targets for which -mcmodel is invalid.
HOST_LIBGCC2_CFLAGS += -mno-minimal-toc
# On the modules that deal with IBM 128-bit values, make sure that TFmode uses
# the IBM extended double format. Also turn off gnu attributes on the static
# modules.
IBM128_STATIC_OBJS = ibm-ldouble$(objext) _powitf2$(objext) \
ppc64-fp$(objext) _divtc3$(object) _multc3$(object) \
_fixtfdi$(object) _fixunstfdi$(object) \
_floatditf$(objext) _floatunsditf$(objext)
IBM128_SHARED_OBJS = $(IBM128_STATIC_OBJS:$(objext):_s$(objext))
IBM128_OBJS = $(IBM128_STATIC_OBJS) $(IBM128_SHARED_OBJS)
IBM128_CFLAGS = -Wno-psabi -mabi=ibmlongdouble -mno-gnu-attribute
$(IBM128_OBJS) : INTERNAL_CFLAGS += $(IBM128_CFLAGS)
# Turn off gnu attributes for long double size on all of the shared library
# modules, but leave it on for the static modules, except for the functions
# that explicitly process IBM 128-bit floating point. Shared libraries only
# have one gnu attribute for the whole library, and it can lead to warnings if
# somebody changes the long double format. We leave it on for the static
# modules to catch mis-compilation errors.
gcc_s_compile += -mno-gnu-attribute