From: Thomas Preudhomme <thomas.preudhomme@foss.arm.com>
To: gcc-patches@gcc.gnu.org
Subject: Fwd: [PATCH, doc/ARM] Remove false affirmation that Thumb cannot use an FPU
Date: Wed, 10 Aug 2016 15:51:00 -0000 [thread overview]
Message-ID: <c31220b3-b023-57ee-2ec3-9c7f4ea66c2a@foss.arm.com> (raw)
In-Reply-To: <4052511d-541d-9b8b-3000-ba09dc314f7f@foss.arm.com>
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Forwarding to gcc-patches which I forgot past patch #1
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GCC documentation for MULTILIB_EXCEPTIONS states that ARM processors cannot use
hardware floating-point in Thumb execution state. This is incorrect since
ARMv7E-M processors can do just that. This patch replace this example with the
case of the meaningless -mfloat-abi=soft -mfpu=* combination of options.
MULTILIB_EXCEPTIONS was indeed use to exclude such a case in
config/arm/t-aprofile until patches preceding this one.
ChangeLog entry is as follows:
*** gcc/ChangeLog ***
2016-08-02 Thomas Preud'homme <thomas.preudhomme@arm.com>
* doc/fragments.texi (MULTILIB_EXCEPTIONS): Replace example with
preventing combination of -mfloat-abi=soft with any -mfpu option.
gccint.pdf builds fine with the patch and display is as expected.
Is this ok for trunk?
Best regards,
Thomas
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diff --git a/gcc/doc/fragments.texi b/gcc/doc/fragments.texi
index b6d8541c8ca820fa732363a05221e2cd4d1251c2..a060635c9cee7374d9d187858ac87acdd08860f2 100644
--- a/gcc/doc/fragments.texi
+++ b/gcc/doc/fragments.texi
@@ -117,12 +117,15 @@ specified, there are combinations that should not be built. In that
case, set @code{MULTILIB_EXCEPTIONS} to be all of the switch exceptions
in shell case syntax that should not be built.
-For example the ARM processor cannot execute both hardware floating
-point instructions and the reduced size THUMB instructions at the same
-time, so there is no need to build libraries with both of these
-options enabled. Therefore @code{MULTILIB_EXCEPTIONS} is set to:
+For example on ARM targets @code{-mfloat-abi=soft} requests to use a
+softfloat implementation for floating-point operations. Therefore, it
+does not make sense to find both @code{-mfloat-abi=soft} and an
+@code{mfpu} option on the command line so @code{MULTILIB_EXCEPTIONS}
+could contain the following exception (assuming that @code{-mfloat-abi}
+comes after in MULTILIB_OPTIONS and given that soft is the default
+value):
@smallexample
-*mthumb/*mhard-float*
+*mfpu=*
@end smallexample
@findex MULTILIB_REQUIRED
next parent reply other threads:[~2016-08-10 15:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4052511d-541d-9b8b-3000-ba09dc314f7f@foss.arm.com>
2016-08-10 15:51 ` Thomas Preudhomme [this message]
2016-08-11 3:09 ` Sandra Loosemore
2016-08-11 10:31 ` Thomas Preudhomme
2016-08-17 10:50 ` Fwd: [PATCH, doc/ARM, ping] " Thomas Preudhomme
2016-08-18 6:01 ` Fwd: [PATCH, doc/ARM] " Sandra Loosemore
2016-08-18 10:05 ` Richard Earnshaw (lists)
2016-08-18 20:00 ` Sandra Loosemore
2016-08-18 10:22 ` Thomas Preudhomme
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