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Unable to run the neon instructions in startup_Cortex-R52

Praveenk0447

Hi,

I am planning to execute few neon add instructions using startup_Cortex-R52 example project. I have created assembly file with neon instructions and added it to project. I have modified the target settings to use -march "armv8-r", mfpu to "neon" and float-abi to "Hardware(Software FPO Linkage)".

Is there any startup code that I need to add for enabling neon extension. Let me know how can I proceed regarding this.

Thanks,

Praveen. 

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  • 0

    Hi Praveen

    The startup_Cortex-R52 example already has the necessary code to enable NEON in startup.S:

    #ifdef __ARM_FP
//----------------------------------------------------------------
// Enable access to VFP by enabling access to Coprocessors 10 and 11.
// Enables Full Access i.e. in both privileged and non privileged modes
//----------------------------------------------------------------

        MRC     p15, 0, r0, c1, c0, 2      // Read Coprocessor Access Control Register (CPACR)
        ORR     r0, r0, #(0xF << 20)       // Enable access to CP 10 & 11
        MCR     p15, 0, r0, c1, c0, 2      // Write Coprocessor Access Control Register (CPACR)
        ISB

//----------------------------------------------------------------
// Switch on the VFP hardware
//----------------------------------------------------------------

        MOV     r0, #0x40000000
        VMSR    FPEXC, r0                   // Write FPEXC register, EN bit set
#endif

    In All Tools Settings > Target, I suggest you set
    Target CPU = Cortex-R52
    Target FPU = Armv8 (Neon)
    Float ABI = Hardware

    which results in the compiler command-line:
    armclang --target=arm-arm-none-eabi -mcpu=cortex-r52 -mfpu=neon-fp-armv8 -mfloat-abi=hard

    Hope this helps

    Stephen

Reply
  • 0

    Hi Praveen

    The startup_Cortex-R52 example already has the necessary code to enable NEON in startup.S:

    #ifdef __ARM_FP
//----------------------------------------------------------------
// Enable access to VFP by enabling access to Coprocessors 10 and 11.
// Enables Full Access i.e. in both privileged and non privileged modes
//----------------------------------------------------------------

        MRC     p15, 0, r0, c1, c0, 2      // Read Coprocessor Access Control Register (CPACR)
        ORR     r0, r0, #(0xF << 20)       // Enable access to CP 10 & 11
        MCR     p15, 0, r0, c1, c0, 2      // Write Coprocessor Access Control Register (CPACR)
        ISB

//----------------------------------------------------------------
// Switch on the VFP hardware
//----------------------------------------------------------------

        MOV     r0, #0x40000000
        VMSR    FPEXC, r0                   // Write FPEXC register, EN bit set
#endif

    In All Tools Settings > Target, I suggest you set
    Target CPU = Cortex-R52
    Target FPU = Armv8 (Neon)
    Float ABI = Hardware

    which results in the compiler command-line:
    armclang --target=arm-arm-none-eabi -mcpu=cortex-r52 -mfpu=neon-fp-armv8 -mfloat-abi=hard

    Hope this helps

    Stephen

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