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arch: arm: aarch32: Add half-precision floating-point configs

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This commit adds the half-precision (16-bit) floating-point
configurations to the ARM AArch32 architectures.

Enabling CONFIG_FP16 has the effect of specifying `-mfp16-format`
option (in case of GCC) which allows using the half-precision floating
point types such as `__fp16` and `_Float16`.

Note that this configuration can be used regardless of whether a
hardware FPU is available or supports half-precision operations.

When an FP16-capable FPU is not available, the compiler will
automatically provide the software emulations.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>
This commit is contained in:
Stephanos Ioannidis 2021-08-18 21:04:45 +09:00 • committed by Carles Cufí
commit 41fd6e003c
2 changed files with 41 additions and 0 deletions
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31
arch/arm/core/aarch32/Kconfig
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@ -260,6 +260,37 @@ config FP_SOFTABI
endchoice
config FP16
bool "Half-precision floating point support"
default y
help
This option enables the half-precision (16-bit) floating point support
via the `__fp16` (both IEEE and ARM alternative formats) and the
`_Float16` (IEEE format only) types.
choice
prompt "FP16 format"
default FP16_IEEE
depends on FP16
config FP16_IEEE
bool "FP16 IEEE format"
help
This option selects the IEEE 754-2008 format for FP16. This format can
represent normalized values in the range of 2^(-14) to 65504. There are
11 bits of significand precision, approximately 3 decimal digits.
config FP16_ALT
bool "FP16 ARM alternative format"
help
This option selects the ARM alternative format for FP16. This
representation is similar to the IEEE 754-2008 format, but does not
support infinites or NaNs. Instead, the range of exponents is extended,
so that this format can represent normalized values in the range of
2^(-14) to 131008.
endchoice
rsource "cortex_m/Kconfig"
rsource "cortex_a_r/Kconfig"

10
cmake/compiler/gcc/target_arm.cmake
View file

@ -38,3 +38,13 @@ if(CONFIG_FPU)
list(APPEND TOOLCHAIN_LD_FLAGS -mfloat-abi=hard)
endif()
endif()
if(CONFIG_FP16)
if (CONFIG_FP16_IEEE)
list(APPEND TOOLCHAIN_C_FLAGS -mfp16-format=ieee)
list(APPEND TOOLCHAIN_LD_FLAGS -mfp16-format=ieee)
elseif(CONFIG_FP16_ALT)
list(APPEND TOOLCHAIN_C_FLAGS -mfp16-format=alternative)
list(APPEND TOOLCHAIN_LD_FLAGS -mfp16-format=alternative)
endif()
endif()