i.MX6UL Hard & Soft Floating with Forlinx OKMX6UL-C - Blog - Forlinx Embedded Technology Co., Ltd.

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How to Take i.MX6UL to do Hard-floating and Soft-floating

i.MX 6UltraLite (for short i.MX 6UL) is a single-core ARM Cortex-A7 SoC running at speed at up to 528MHz, integrated with NEON MPE (Media Processing Engine) Co-processor which is applicable for IoT, E-payment, smart home, power management and other related applications.

How to do hard-floating and soft-floating by i.MX6UL platform?

Here we'll take Forlinx OKMX6UL-C for demonstration(product details please refer to (https://www.forlinx.net/product/i.mx6ul-39.html):

How to Take i.MX6UL to do Hard-floating and Soft-floating

Follow below steps to do hard-floating:

arm-linux-gcc -march=armv7-a -mfpu=neon -mfloat-abi=hard -o test test.c

add in compiling parameters -mfloat-abi=hard, and take arm-linux-readelf -A test to check as below

Attribute Section: aeabi
File Attributes
  Tag_CPU_name: "7-A"
  Tag_CPU_arch: v7
  Tag_CPU_arch_profile: Application
  Tag_ARM_ISA_use: Yes
  Tag_THUMB_ISA_use: Thumb-2
  Tag_FP_arch: VFPv3
  Tag_Advanced_SIMD_arch: NEONv1
  Tag_ABI_PCS_wchar_t: 4
  Tag_ABI_FP_denormal: Needed
  Tag_ABI_FP_exceptions: Needed
  Tag_ABI_FP_number_model: IEEE 754
  Tag_ABI_align_needed: 8-byte
  Tag_ABI_align_preserved: 8-byte, except leaf SP
  Tag_ABI_enum_size: int
  Tag_ABI_HardFP_use: SP and DP
  Tag_ABI_VFP_args: VFP registers
  Tag_DIV_use: Not allowed

we can get that it takes Tag_ABI_VFP_args: VFP registers for hard-floating

Follow below steps to do soft-floating

arm-linux-gcc -o teset_soft test.c and take arm-linux-readelf -A test_soft to check as below:

Attribute Section: aeabi
File Attributes
  Tag_CPU_name: "ARM10TDMI"
  Tag_CPU_arch: v5T
  Tag_ARM_ISA_use: Yes
  Tag_THUMB_ISA_use: Thumb-1
  Tag_ABI_PCS_wchar_t: 4
  Tag_ABI_FP_denormal: Needed
  Tag_ABI_FP_exceptions: Needed
  Tag_ABI_FP_number_model: IEEE 754
  Tag_ABI_align_needed: 8-byte
  Tag_ABI_align_preserved: 8-byte, except leaf SP
  Tag_ABI_enum_size: int
  Tag_DIV_use: Not allowed

VFP was not used.

Testing result:

Do a billion times of computing, hard-floating time is one minute thirty four point 8, and soft-floating time is four minutes nineteen point seven.