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[ARM] Rework selection of feature bits to base build attributes on 

=== Context ===

This patch is part of a patch series to add support for ARMv8-R
architecture. Its purpose is to set the feature bits on which to decide
what the build attributes should be according to the mode
(autodetection, user specified architecture or CPU, or
-march/-mcpu=all).

=== Motivation ===

Currently, the flags variable which is used to determine the build
attribute is constructed from the instruction used (arm_arch_used and
thumb_arch_used) as well as the user specified architecture or CPU
(selected_cpu). This means when several .arch are specified the
resulting feature bits can be such that no architecture provide them
all and can thus result in incorrect Tag_CPU_arch. See for instance
what having both .arch armv8-a and .arch armv8-m.base would result in.
This is not caught by the testsuite because of further bugs in the
Tag_CPU_arch build attribute value selection logic (see next patch in
the series).

=== Patch description ===

As one would expect, this patch solves the problem by setting flags
from feature bits used if in autodetection mode [1] and from
selected_cpu otherwise. The logic to set arm_ext_v1, arm_ext_v4t and
arm_ext_os feature bits is also moved to only run in autodetection mode
since otherwise the architecture or CPU would have a consistent set of
feature bits already.

[1] No architecture or CPU was specified by the user

2017-06-21  Thomas Preud'homme  <thomas.preudhomme@arm.com>

gas/
	* config/tc-arm.c (aeabi_set_public_attributes): Populate flags from
	feature bits used or selected_cpu depending on whether a CPU was
	selected by the user.
This commit is contained in:
Thomas Preud'homme 2017-06-21 14:57:53 +01:00
parent bdab445c82
commit 54bab2816d
2 changed files with 32 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
gas/ChangeLog
View File

@ -1,3 +1,9 @@
2017-06-21 Thomas Preud'homme <thomas.preudhomme@arm.com>
* config/tc-arm.c (aeabi_set_public_attributes): Populate flags from
feature bits used or selected_cpu depending on whether a CPU was
selected by the user.
2017-06-21 Thomas Preud'homme <thomas.preudhomme@arm.com>
* config/tc-arm.c (aeabi_set_public_attributes): Test *mcpu_ext_opt to

44
gas/config/tc-arm.c
View File

@ -26605,19 +26605,33 @@ aeabi_set_public_attributes (void)
arm_feature_set arm_arch_v8m_base = ARM_ARCH_V8M_BASE;
const cpu_arch_ver_table *p;
/* Choose the architecture based on the capabilities of the requested cpu
(if any) and/or the instructions actually used. */
ARM_MERGE_FEATURE_SETS (flags, arm_arch_used, thumb_arch_used);
/* Autodetection mode, choose the architecture based the instructions
actually used. */
if (no_cpu_selected ())
{
ARM_MERGE_FEATURE_SETS (flags, arm_arch_used, thumb_arch_used);
if (ARM_CPU_HAS_FEATURE (arm_arch_used, arm_arch_any))
ARM_MERGE_FEATURE_SETS (flags, flags, arm_ext_v1);
if (ARM_CPU_HAS_FEATURE (thumb_arch_used, arm_arch_any))
ARM_MERGE_FEATURE_SETS (flags, flags, arm_ext_v4t);
/* We need to make sure that the attributes do not identify us as v6S-M
when the only v6S-M feature in use is the Operating System
Extensions. */
if (ARM_CPU_HAS_FEATURE (flags, arm_ext_os))
if (!ARM_CPU_HAS_FEATURE (flags, arm_arch_v6m_only))
ARM_CLEAR_FEATURE (flags, flags, arm_ext_os);
/* Code run during relaxation relies on selected_cpu being set. */
selected_cpu = flags;
}
/* Otherwise, choose the architecture based on the capabilities of the
requested cpu. */
else
flags = selected_cpu;
ARM_MERGE_FEATURE_SETS (flags, flags, *mfpu_opt);
ARM_MERGE_FEATURE_SETS (flags, flags, selected_cpu);
if (ARM_CPU_HAS_FEATURE (arm_arch_used, arm_arch_any))
ARM_MERGE_FEATURE_SETS (flags, flags, arm_ext_v1);
if (ARM_CPU_HAS_FEATURE (thumb_arch_used, arm_arch_any))
ARM_MERGE_FEATURE_SETS (flags, flags, arm_ext_v4t);
selected_cpu = flags;
/* Allow the user to override the reported architecture. */
if (object_arch)
@ -26626,12 +26640,6 @@ aeabi_set_public_attributes (void)
ARM_MERGE_FEATURE_SETS (flags, flags, *object_arch);
}
/* We need to make sure that the attributes do not identify us as v6S-M
when the only v6S-M feature in use is the Operating System Extensions. */
if (ARM_CPU_HAS_FEATURE (flags, arm_ext_os))
if (!ARM_CPU_HAS_FEATURE (flags, arm_arch_v6m_only))
ARM_CLEAR_FEATURE (flags, flags, arm_ext_os);
tmp = flags;
arch = 0;
for (p = cpu_arch_ver; p->val; p++)