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[wasm] Implement I2 and I4 shuffles in the jiterpreter #86469

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Merged
kg merged 2 commits into from
May 19, 2023
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[wasm] Implement I2 and I4 shuffles in the jiterpreter #86469

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bc8ca49
Implement a wasm lowering for V128_I2_SHUFFLE in the jiterpreter so B…
kg May 18, 2023
f2f24e5
Generalize shuffles and add I4 support
kg May 18, 2023
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52 changes: 52 additions & 0 deletions src/mono/wasm/runtime/jiterpreter-trace-generator.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3245,13 +3245,65 @@ function emit_simd_3(builder: WasmBuilder, ip: MintOpcodePtr, index: SimdIntrins
builder.appendU8(WasmOpcode.i32_eqz);
append_stloc_tail(builder, getArgU16(ip, 1), WasmOpcode.i32_store);
return true;
case SimdIntrinsic3.V128_I2_SHUFFLE:
case SimdIntrinsic3.V128_I4_SHUFFLE:
// FIXME: I8
// FIXME: Many uses of these shuffles have constant shuffle indices,
// which we could convert into bytes at compile time for vastly improved performance
return emit_shuffle(builder, ip, index === SimdIntrinsic3.V128_I2_SHUFFLE ? 8 : 4);
default:
return false;
}

return false;
}

// implement i16 and i32 shuffles on top of wasm's only shuffle opcode by expanding the
// element shuffle indices into byte indices
function emit_shuffle(builder: WasmBuilder, ip: MintOpcodePtr, elementCount: number): boolean {
const elementSize = 16 / elementCount;
mono_assert((elementSize === 2) || (elementSize === 4), "Unsupported shuffle element size");
builder.local("pLocals");
// Load vec
append_ldloc(builder, getArgU16(ip, 2), WasmOpcode.PREFIX_simd, WasmSimdOpcode.v128_load);
// Load indices (in chars)
append_ldloc(builder, getArgU16(ip, 3), WasmOpcode.PREFIX_simd, WasmSimdOpcode.v128_load);
// There's no direct narrowing opcode for i32 -> i8, so we have to do two steps :(
if (elementCount === 4) {
// i32{lane0 ... lane3} -> i16{lane0 ... lane3, 0 ...}
builder.i52_const(0);
builder.appendSimd(WasmSimdOpcode.i64x2_splat);
builder.appendSimd(WasmSimdOpcode.i16x8_narrow_i32x4_u);
}
// Load a zero vector (narrow takes two vectors)
builder.i52_const(0);
builder.appendSimd(WasmSimdOpcode.i64x2_splat);
// i16{lane0 ... lane7} -> i8{lane0 ... lane7, 0 ...}
builder.appendSimd(WasmSimdOpcode.i8x16_narrow_i16x8_u);
// i8{0, 1, 2, 3 ...} -> i8{0, 0, 1, 1, 2, 2, 3, 3 ...}
builder.appendSimd(WasmSimdOpcode.v128_const);
for (let i = 0; i < elementCount; i++) {
for (let j = 0; j < elementSize; j++)
builder.appendU8(i);
}
builder.appendSimd(WasmSimdOpcode.i8x16_swizzle);
// multiply indices by 2 to scale from char indices to byte indices
builder.i32_const(elementCount === 4 ? 2 : 1);
builder.appendSimd(WasmSimdOpcode.i8x16_shl);
// now add 1 to the secondary lane of each char
builder.appendSimd(WasmSimdOpcode.v128_const);
for (let i = 0; i < elementCount; i++) {
for (let j = 0; j < elementSize; j++)
builder.appendU8(j);
}
// we can do a bitwise or since we know we previously multiplied all the lanes by 2
builder.appendSimd(WasmSimdOpcode.v128_or);
// we now have two vectors on the stack, the values and the byte indices
builder.appendSimd(WasmSimdOpcode.i8x16_swizzle);
append_simd_store(builder, ip);
return true;
}

function emit_simd_4(builder: WasmBuilder, ip: MintOpcodePtr, index: SimdIntrinsic4): boolean {
const simple = <WasmSimdOpcode>cwraps.mono_jiterp_get_simd_opcode(3, index);
if (simple) {
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