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POUse C variables in ARM Neon assembly
 

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  1. POUse C variables in ARM Neon assembly
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    <p>I've a problem using C/C++ variables inside ARM NEON assembly code written in:</p> <pre><code>__asm__ __volatile() </code></pre> <p>I've read about the following possibilities, which should move values from ARM to NEON registers. Each of the following possibilities cause a Fatal Signal in my Android application:</p> <pre><code>VDUP.32 d0, %[variable] VMOV.32 d0[0], %[variable] </code></pre> <p>the input argument list includes:</p> <pre><code>[variable] "r" (variable) </code></pre> <p>The only way I have success is using a load:</p> <pre><code>int variable = 0; int *address = &amp;variable; .... VLD1.32 d0[0], [%[address]] : [address] "+r" (address) </code></pre> <p>But I think a load is not the best for performance if I don't need to modify the variable, and I also need to understand how to move data from ARM to NEON registers for other purposes.</p> <p><strong>EDIT</strong>: added example as requested, both possibility 1 and 2 result in a "fatal signal". I know in this example NEON assembly simply should modify first 2 elements of "array[4]".</p> <pre><code>int c = 10; int *array4; array4 = new int[64]; for(int i = 0; i &lt; 64; i++){ array4[i] = 100*i; } __asm__ __volatile ("VLD1.32 d0, [%[array4]] \n\t" "VMOV.32 d1[0], %[c] \n\t" //this is possibility 1 "VDUP.32 d2, %[c] \n\t" //this is possibility 2 "VMUL.S32 d0, d0, d2 \n\t" "VST1.32 d0, [%[output_array1]] \n\t" : [output_array1] "=r" (output_array1) : [c] "r" (c), [array4] "r" (array4) : "d0", "d1", "d2"); </code></pre>
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    1. USAlessandro Gaietta
    1. USAlessandro Gaietta
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    1. COYou did remember to clobber d0, right?
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      1. POUse C variables in ARM Neon assembly
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    2. COYou should probably post some real code or we can't be sure.
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      1. POUse C variables in ARM Neon assembly
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    3. COI wonder if it has something to do with how `%[variable]` is interpreted by the compiler. After all, the `VLD1` instruction needs square brackets around the `address` reference.
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      1. POUse C variables in ARM Neon assembly
      1. USDrew McGowen
 

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