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7794d6c8f8
Current build infra uses ARM_ARCH_MAJOR/MINOR to come up with march version and uses that march version with the compiler. However in certain situations this is not ideal, like for example when we build with gcc-11 which supports only till march=armv8.5 but we need to build for 8.8 build, this means we need to bump down MAJOR/MINOR and we can't rely on major and minor values from the platform to select march value and build infra doesn't even try to compile and fails with not supported MAJOR/MINOR. By adding a march build helper we try to check if compiler supports given march value from MAJOR/MINOR values from platform, if compiler doesn't support then we try to check what's the max or best supported march version by compiler and choose that march value and try to compile with that. This is a supportive mechanism which will decouple march reliance on MAJOR/MINOR values from platform and will pave way for setting up enabling of features based on MAJOR/MINOR without worrying about the compiler not supporting given MAJOR/MINOR. Also in TF-A we use generic instructions without much reliance or need for exact march necessity. So enabling and building features from armv-8.8 using an armv-8.5 march value is still going to be fine. Please note: Platforms are free to freeze their march values using `MARCH_DIRECTIVE`. In absence of this define we are going to poke the compiler and come up with a potential march value. Change-Id: I673061a269ec9018ff12e75dc375979f5e33b7d1 Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
85 lines
3.3 KiB
Makefile
85 lines
3.3 KiB
Makefile
#
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# Copyright (c) 2023, Arm Limited. All rights reserved.
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#
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# SPDX-License-Identifier: BSD-3-Clause
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#
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# This build helper makefile is used to determine a suitable march build
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# option to be used, based on platform provided ARM_ARCH_MAJOR/MINOR
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# data and compiler supported march version.
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# Set the compiler's target architecture profile based on
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# ARM_ARCH_MAJOR and ARM_ARCH_MINOR options.
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# This is used to collect available march values from compiler.
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# Example on a gcc-12.2 arm64 toolchain it will look like:
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# [...]
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#./aarch64-none-elf-gcc --target-help -march=foo
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# cc1: error: unknown value 'foo' for '-march'
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# cc1: note: valid arguments are: armv8-a armv8.1-a armv8.2-a armv8.3-a armv8.4-a armv8.5-a
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# armv8.6-a armv8.7-a armv8.8-a armv8-r armv9-a
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# [...]
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#
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GCC_MARCH_OUTPUT := $(shell $(CC) -march=foo -Q --help=target -v 2>&1)
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# This function is used to find the best march value supported by the given compiler.
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# We try to use `GCC_MARCH_OUTPUT` which has verbose message with supported march values we filter that
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# to find armvX.Y-a or armvX-a values, then filter the best supported arch based on ARM_ARCH_MAJOR.
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#
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# Example on a gcc-12.2 arm64 toolchain this will return armv9-a if platform requested for armv9.2-a
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# Similarly on gcc 11.3 it would return armv8.6-a if platform requested armv8.8-a
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define major_best_avail_march
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$(1) := $(lastword $(filter armv$(ARM_ARCH_MAJOR)% ,$(filter armv%-a, $(GCC_MARCH_OUTPUT))))
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endef
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# This function is used to just return latest march value supported by the given compiler.
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#
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# Example: this would return armv8.6-a on a gcc-11.3 when platform requested for armv9.0-a
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#
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# Thus this function should be used in conjunction with major_best_avail_march, when best match
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# is not found it should be ok to try with lastest known supported march value from the
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# compiler.
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define latest_match_march
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$(1) := $(lastword $(filter armv%-a, $(GCC_MARCH_OUTPUT)))
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endef
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ifdef MARCH_DIRECTIVE
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march-directive := $(MARCH_DIRECTIVE)
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else
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ifeq (${ARM_ARCH_MINOR},0)
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provided-march = armv${ARM_ARCH_MAJOR}-a
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else
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provided-march = armv${ARM_ARCH_MAJOR}.${ARM_ARCH_MINOR}-a
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endif
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ifeq ($(findstring clang,$(notdir $(CC))),)
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# We expect from Platform to provide a correct Major/Minor value but expecting something
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# from compiler with unsupported march means we shouldn't fail without trying anything,
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# so here we try to find best supported march value and use that for compilation.
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# If we don't support current march version from gcc compiler, try with lower arch based on
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# availability. In TF-A there is no hard rule for need of higher version march for basic
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# functionality, denying a build on only this fact doesn't look correct, so try with best
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# or latest march values from whats available from compiler.
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ifeq (,$(findstring $(provided-march), $(GCC_MARCH_OUTPUT)))
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$(eval $(call major_best_avail_march, available-march))
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ifeq (, $(available-march))
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$(eval $(call latest_match_march, available-march))
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endif
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# If we fail to come up with any available-march value so far, don't update
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# provided-march and thus allow the build to fail using the provided-march
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# which is derived based on arch_major and arch_minor values.
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ifneq (,$(available-march))
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provided-march := ${available-march}
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endif
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endif # provided-march supported
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endif # not clang
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march-directive := -march=${provided-march}
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endif # MARCH_DIRECTIVE
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