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Aarch64 llvm unrecognized instruction mnemonic

AJIT

I am trying to use ARM inline assembly in a C code. I am compiling using aarch64-linux-android-clang version 3.8.243773, the 64 bit llvm toolchain from Android NDK R11.

The inline assembly code is as follows:

__asm__("ssat %w0, #24, %w1\n\t" : "=r" (val) : "r" (val) : );

The syntax of inline assembly code is correct and it compiles the syntax code as such but the assembler spits out a error saying

error: unrecognized instruction mnemonic ssat

What is the problem here? Doesn't llvm from the ndk toolchain support this assembly instruction?

How can I fix or workaround this issue?

thanks.

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  • 0 in reply to AJIT
    NEON is not like AVX or MMX, you do not need to "move" to NEON. Just use NEON instructions.
    Anyway AFAICS NEON does not provide saturation either.
    I think the ASM code does not look to bad:
    mov w1, 8388607
    mov w2, -8388608
    cmp w0, w1
    csel w0, w0, w1, le
    cmp w0, w2
    csel w0, w0, w2, ge

    Of course, nothing compared to a single instruction. :-)
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  • 0 in reply to AJIT
    NEON is not like AVX or MMX, you do not need to "move" to NEON. Just use NEON instructions.
    Anyway AFAICS NEON does not provide saturation either.
    I think the ASM code does not look to bad:
    mov w1, 8388607
    mov w2, -8388608
    cmp w0, w1
    csel w0, w0, w1, le
    cmp w0, w2
    csel w0, w0, w2, ge

    Of course, nothing compared to a single instruction. :-)
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