SIMD on Playdate


The 3D Library example in the SDK contains the following SIMD headers:

  • core_cm7.h
  • core_cmFunc.h
  • core_cmInstr.h
  • core_cmSimd.h

They are not included or used at all in the example.

I tried using the headers from the example, but GCC assembler doesn't recognise the assembly instructions.
I do nothing special at build time, everything is stock from C_API/buildsupport.

// sets __FPU_USED but these headers expect __FPU_PRESENT
#define __FPU_PRESENT 1
#include "core_cm7.h"
int32_t accum = 0;
int32_t a = 10 << 16;
a |= 5;
int32_t b = 2 << 16;
b |= 7;
accum = __SMLAD(a, b, accum);

include/core_cmSimd.h:507: Error: no such instruction: `smlad %eax,%eax,%edx,%ecx'

From a quick glance at ARM's intrinsic documentation, Cortex M7 should support __SMLAD.
Before I investigate further into this, I'm asking here.

  • Has anyone used SIMD on the Playdate?
  • Are the headers in the 3D Library SDK appropriate for Cortex M7?
  • Is there any extra compiler flags needed for the assembler to recognise these instructions?
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I'm not sure how to properly use the smlad instruction but writing inline assembly at least compiles without errors.

As an example, here's how I'm using some inline asm for a saturating add:

static inline i16 saturating_add_i16(i16 i, i16 j) {
    __asm__ volatile("qadd16 %0, %0, %1" : "+r"(i) : "r"(j));
    return i;
1 Like


Seeing your snippet made me realize my issue was actually very simple.

I only needed to wrap the SIMD around TARGET_PLAYDATE guards. Since the default SDK makefile will compile for the simulator also. The error I had was only when not cross-compiling in arm.

I can run SIMD on the device with this:

#define __FPU_PRESENT 1
#include "core_cm7.h"

accum = __SMLAD(a, b, accum);