armv8-m: GCC/ArmClang: Remove redundant constant pools #1035
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Currently in Armv8-M GCC/ArmClang ports, constant pool is used to define literals needed for `ldr` instructions. However, those constant pools are defined with `.align 4` which increases code size. Instead of defining the constant pool with `.align 4`, let the compiler hanlde the constant pool and the required alignment. Signed-off-by: Devaraj Ranganna <devaraj.ranganna@arm.com>
laroche
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Apr 18, 2024
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kar-rahul-aws
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Apr 18, 2024
aggarg
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Apr 18, 2024
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Description
Currently in Armv8-M GCC/ArmClang ports, constant pool is used to define literals needed for
ldrinstruction. However, those constant pools are defined with.align 4which increases code size. Instead of defining the constant pool with.align 4, let the compiler hanlde the constant pool and the required alignment.Benchmarking these changes using Cortex-M85 (Corstone-315) and blinky application in https://github.com/FreeRTOS/iot-reference-arm-corstone3xx/tree/main/applications/blinky shows a code size reduction of
72 bytes (GCC)and56 bytes (ArmClang).Additional info:
Armv8-M IAR port doesn't use any constant pool. With these changes all three ports GCC/ArmClang/IAR are aligned.
Test Steps
Validated the changes using GCC and ArmClang and using blinky application in https://github.com/FreeRTOS/iot-reference-arm-corstone3xx/tree/main/applications/blinky and:
Still to validate:
Checklist:
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