skia2/tests/SkVMTest.cpp

/*
 * Copyright 2019 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "include/core/SkColorPriv.h"
#include "include/private/SkColorData.h"
#include "src/core/SkVM.h"
#include "tests/Test.h"
#include "tools/Resources.h"
#include "tools/SkVMBuilders.h"

using Fmt = SrcoverBuilder_F32::Fmt;
const char* fmt_name(Fmt fmt) {
    switch (fmt) {
        case Fmt::A8:        return "A8";
        case Fmt::G8:        return "G8";
        case Fmt::RGBA_8888: return "RGBA_8888";
    }
    return "";
}

namespace {
    using namespace skvm;

    struct V { Val id; };
    struct R { Reg id; };
    struct Shift { int bits; };
    struct Splat { int bits; };
    struct Hex   { int bits; };

    static void write(SkWStream* o, const char* s) {
        o->writeText(s);
    }

    static void write(SkWStream* o, Arg a) {
        write(o, "arg(");
        o->writeDecAsText(a.ix);
        write(o, ")");
    }
    static void write(SkWStream* o, V v) {
        write(o, "v");
        o->writeDecAsText(v.id);
    }
    static void write(SkWStream* o, R r) {
        write(o, "r");
        o->writeDecAsText(r.id);
    }
    static void write(SkWStream* o, Shift s) {
        o->writeDecAsText(s.bits);
    }
    static void write(SkWStream* o, Splat s) {
        float f;
        memcpy(&f, &s.bits, 4);
        o->writeHexAsText(s.bits);
        write(o, " (");
        o->writeScalarAsText(f);
        write(o, ")");
    }
    static void write(SkWStream* o, Hex h) {
        o->writeHexAsText(h.bits);
    }

    template <typename T, typename... Ts>
    static void write(SkWStream* o, T first, Ts... rest) {
        write(o, first);
        write(o, " ");
        write(o, rest...);
    }

    static void dump(const Builder& builder, SkWStream* o) {
        const std::vector<Builder::Instruction> program = builder.program();

        o->writeDecAsText(program.size());
        o->writeText(" values:\n");
        for (Val id = 0; id < (Val)program.size(); id++) {
            const Builder::Instruction& inst = program[id];
            Op  op = inst.op;
            Val  x = inst.x,
                 y = inst.y,
                 z = inst.z;
            int imm = inst.imm;
            switch (op) {
                case Op::store8:  write(o, "store8" , Arg{imm}, V{x}); break;
                case Op::store32: write(o, "store32", Arg{imm}, V{x}); break;

                case Op::load8:  write(o, V{id}, "= load8" , Arg{imm}); break;
                case Op::load32: write(o, V{id}, "= load32", Arg{imm}); break;

                case Op::splat:  write(o, V{id}, "= splat", Splat{imm}); break;

                case Op::add_f32: write(o, V{id}, "= add_f32", V{x}, V{y}      ); break;
                case Op::sub_f32: write(o, V{id}, "= sub_f32", V{x}, V{y}      ); break;
                case Op::mul_f32: write(o, V{id}, "= mul_f32", V{x}, V{y}      ); break;
                case Op::div_f32: write(o, V{id}, "= div_f32", V{x}, V{y}      ); break;
                case Op::mad_f32: write(o, V{id}, "= mad_f32", V{x}, V{y}, V{z}); break;

                case Op::add_i32: write(o, V{id}, "= add_i32", V{x}, V{y}); break;
                case Op::sub_i32: write(o, V{id}, "= sub_i32", V{x}, V{y}); break;
                case Op::mul_i32: write(o, V{id}, "= mul_i32", V{x}, V{y}); break;

                case Op::sub_i16x2: write(o, V{id}, "= sub_i16x2", V{x}, V{y}); break;
                case Op::mul_i16x2: write(o, V{id}, "= mul_i16x2", V{x}, V{y}); break;
                case Op::shr_i16x2: write(o, V{id}, "= shr_i16x2", V{x}, Shift{imm}); break;

                case Op::bit_and  : write(o, V{id}, "= bit_and"  , V{x}, V{y}); break;
                case Op::bit_or   : write(o, V{id}, "= bit_or"   , V{x}, V{y}); break;
                case Op::bit_xor  : write(o, V{id}, "= bit_xor"  , V{x}, V{y}); break;
                case Op::bit_clear: write(o, V{id}, "= bit_clear", V{x}, V{y}); break;

                case Op::shl: write(o, V{id}, "= shl", V{x}, Shift{imm}); break;
                case Op::shr: write(o, V{id}, "= shr", V{x}, Shift{imm}); break;
                case Op::sra: write(o, V{id}, "= sra", V{x}, Shift{imm}); break;

                case Op::extract: write(o, V{id}, "= extract", V{x}, Shift{imm}, V{y}); break;
                case Op::pack:    write(o, V{id}, "= pack",    V{x}, V{y}, Shift{imm}); break;

                case Op::bytes:   write(o, V{id}, "= bytes", V{x}, Hex{imm}); break;

                case Op::to_f32: write(o, V{id}, "= to_f32", V{x}); break;
                case Op::to_i32: write(o, V{id}, "= to_i32", V{x}); break;
            }

            write(o, "\n");
        }
    }

    static void dump(const Program& program, SkWStream* o) {
        const std::vector<Program::Instruction> instructions = program.instructions();
        const int nregs = program.nregs();
        const int loop  = program.loop();

        o->writeDecAsText(nregs);
        o->writeText(" registers, ");
        o->writeDecAsText(instructions.size());
        o->writeText(" instructions:\n");
        for (int i = 0; i < (int)instructions.size(); i++) {
            if (i == loop) {
                write(o, "loop:\n");
            }
            const Program::Instruction& inst = instructions[i];
            Op   op = inst.op;
            Reg   d = inst.d,
                  x = inst.x,
                  y = inst.y,
                  z = inst.z;
            int imm = inst.imm;
            switch (op) {
                case Op::store8:  write(o, "store8" , Arg{imm}, R{x}); break;
                case Op::store32: write(o, "store32", Arg{imm}, R{x}); break;

                case Op::load8:  write(o, R{d}, "= load8" , Arg{imm}); break;
                case Op::load32: write(o, R{d}, "= load32", Arg{imm}); break;

                case Op::splat:  write(o, R{d}, "= splat", Splat{imm}); break;

                case Op::add_f32: write(o, R{d}, "= add_f32", R{x}, R{y}      ); break;
                case Op::sub_f32: write(o, R{d}, "= sub_f32", R{x}, R{y}      ); break;
                case Op::mul_f32: write(o, R{d}, "= mul_f32", R{x}, R{y}      ); break;
                case Op::div_f32: write(o, R{d}, "= div_f32", R{x}, R{y}      ); break;
                case Op::mad_f32: write(o, R{d}, "= mad_f32", R{x}, R{y}, R{z}); break;

                case Op::add_i32: write(o, R{d}, "= add_i32", R{x}, R{y}); break;
                case Op::sub_i32: write(o, R{d}, "= sub_i32", R{x}, R{y}); break;
                case Op::mul_i32: write(o, R{d}, "= mul_i32", R{x}, R{y}); break;

                case Op::sub_i16x2: write(o, R{d}, "= sub_i16x2", R{x}, R{y}); break;
                case Op::mul_i16x2: write(o, R{d}, "= mul_i16x2", R{x}, R{y}); break;
                case Op::shr_i16x2: write(o, R{d}, "= shr_i16x2", R{x}, Shift{imm}); break;

                case Op::bit_and  : write(o, R{d}, "= bit_and"  , R{x}, R{y}); break;
                case Op::bit_or   : write(o, R{d}, "= bit_or"   , R{x}, R{y}); break;
                case Op::bit_xor  : write(o, R{d}, "= bit_xor"  , R{x}, R{y}); break;
                case Op::bit_clear: write(o, R{d}, "= bit_clear", R{x}, R{y}); break;

                case Op::shl: write(o, R{d}, "= shl", R{x}, Shift{imm}); break;
                case Op::shr: write(o, R{d}, "= shr", R{x}, Shift{imm}); break;
                case Op::sra: write(o, R{d}, "= sra", R{x}, Shift{imm}); break;

                case Op::extract: write(o, R{d}, "= extract", R{x}, Shift{imm}, R{y}); break;
                case Op::pack:    write(o, R{d}, "= pack",    R{x}, R{y}, Shift{imm}); break;

                case Op::bytes: write(o, R{d}, "= bytes", R{x}, Hex{imm}); break;

                case Op::to_f32: write(o, R{d}, "= to_f32", R{x}); break;
                case Op::to_i32: write(o, R{d}, "= to_i32", R{x}); break;
            }
            write(o, "\n");
        }
    }

    static void dump(const Builder& builder, const Program& program, SkWStream* o) {
        dump(builder, o);
        o->writeText("\n");
        dump(program, o);
        o->writeText("\n");
    }

}  // namespace


DEF_TEST(SkVM, r) {
    SkDynamicMemoryWStream buf;

    // Write all combinations of SrcoverBuilder_F32
    for (int s = 0; s < 3; s++)
    for (int d = 0; d < 3; d++) {
        auto srcFmt = (Fmt)s,
             dstFmt = (Fmt)d;
        SrcoverBuilder_F32 builder{srcFmt, dstFmt};
        skvm::Program program = builder.done();

        buf.writeText(fmt_name(srcFmt));
        buf.writeText(" over ");
        buf.writeText(fmt_name(dstFmt));
        buf.writeText("\n");
        dump(builder, program, &buf);
    }

    // Write the I32 Srcovers also.
    {
        SrcoverBuilder_I32_Naive builder;
        skvm::Program program = builder.done();
        buf.writeText("I32 (Naive) 8888 over 8888\n");
        dump(builder, program, &buf);
    }
    {
        SrcoverBuilder_I32 builder;
        skvm::Program program = builder.done();
        buf.writeText("I32 8888 over 8888\n");
        dump(builder, program, &buf);
    }
    {
        SrcoverBuilder_I32_SWAR builder;
        skvm::Program program = builder.done();
        buf.writeText("I32 (SWAR) 8888 over 8888\n");
        dump(builder, program, &buf);
    }

    sk_sp<SkData> blob = buf.detachAsData();
    {

        sk_sp<SkData> expected = GetResourceAsData("SkVMTest.expected");
        REPORTER_ASSERT(r, expected, "Couldn't load SkVMTest.expected.");
        if (expected) {
            if (blob->size() != expected->size()
                    || 0 != memcmp(blob->data(), expected->data(), blob->size())) {

                ERRORF(r, "SkVMTest expected\n%.*s\nbut got\n%.*s\n",
                       expected->size(), expected->data(),
                       blob->size(), blob->data());
            }

            SkFILEWStream out(GetResourcePath("SkVMTest.expected").c_str());
            if (out.isValid()) {
                out.write(blob->data(), blob->size());
            }
        }
    }

    auto test_8888 = [&](const skvm::Program& program) {
        uint32_t src[9];
        uint32_t dst[SK_ARRAY_COUNT(src)];

        for (int i = 0; i < (int)SK_ARRAY_COUNT(src); i++) {
            src[i] = 0xbb007733;
            dst[i] = 0xffaaccee;
        }

        SkPMColor expected = SkPMSrcOver(src[0], dst[0]);  // 0xff2dad73

        program.eval((int)SK_ARRAY_COUNT(src), src, dst);

        // dst is probably 0xff2dad72.
        for (auto got : dst) {
            auto want = expected;
            for (int i = 0; i < 4; i++) {
                uint8_t d = got  & 0xff,
                        w = want & 0xff;
                REPORTER_ASSERT(r, abs(d-w) < 2);
                got  >>= 8;
                want >>= 8;
            }
        }
    };

    test_8888(SrcoverBuilder_F32{Fmt::RGBA_8888, Fmt::RGBA_8888}.done());
    test_8888(SrcoverBuilder_I32_Naive{}.done());
    test_8888(SrcoverBuilder_I32{}.done());
    test_8888(SrcoverBuilder_I32_SWAR{}.done());

    {
        skvm::Program program = SrcoverBuilder_F32{Fmt::RGBA_8888, Fmt::G8}.done();

        uint32_t src[9];
        uint8_t  dst[SK_ARRAY_COUNT(src)];

        for (int i = 0; i < (int)SK_ARRAY_COUNT(src); i++) {
            src[i] = 0xbb007733;
            dst[i] = 0x42;
        }

        SkPMColor over = SkPMSrcOver(SkPackARGB32(0xbb, 0x33, 0x77, 0x00),
                                     0xff424242);

        uint8_t want = SkComputeLuminance(SkGetPackedR32(over),
                                          SkGetPackedG32(over),
                                          SkGetPackedB32(over));
        program.eval((int)SK_ARRAY_COUNT(src), src, dst);

        for (auto got : dst) {
            REPORTER_ASSERT(r, abs(got-want) < 3);
        }
    }

    {
        skvm::Program program = SrcoverBuilder_F32{Fmt::A8, Fmt::A8}.done();

        uint8_t src[256],
                dst[256];
        for (int i = 0; i < 256; i++) {
            src[i] = 255 - i;
            dst[i] = i;
        }

        program.eval(256, src, dst);

        for (int i = 0; i < 256; i++) {
            uint8_t want = SkGetPackedA32(SkPMSrcOver(SkPackARGB32(src[i], 0,0,0),
                                                      SkPackARGB32(     i, 0,0,0)));
            REPORTER_ASSERT(r, abs(dst[i]-want) < 2);
        }
    }
}

DEF_TEST(SkVM_LoopCounts, r) {
    // Make sure we cover all the exact N we want.

    int buf[64];
    for (int N = 0; N <= (int)SK_ARRAY_COUNT(buf); N++) {
        for (int i = 0; i < (int)SK_ARRAY_COUNT(buf); i++) {
            buf[i] = i;
        }

        // buf[i] += 1
        skvm::Builder b;
        b.store32(b.arg(0),
                  b.add(b.splat(1),
                        b.load32(b.arg(0))));

        skvm::Program program = b.done();
        program.eval(N, buf);

        for (int i = 0; i < N; i++) {
            REPORTER_ASSERT(r, buf[i] == i+1);
        }
        for (int i = N; i < (int)SK_ARRAY_COUNT(buf); i++) {
            REPORTER_ASSERT(r, buf[i] == i);
        }
    }
}


template <typename Fn>
static void test_asm(skiatest::Reporter* r, Fn&& fn, std::initializer_list<uint8_t> expected) {
    uint8_t buf[4096];
    skvm::Assembler a{buf};
    fn(a);

    REPORTER_ASSERT(r, a.size() == expected.size());

    auto got = (const uint8_t*)buf,
         want = expected.begin();
    for (int i = 0; i < (int)std::min(a.size(), expected.size()); i++) {
        REPORTER_ASSERT(r, got[i] == want[i],
                        "byte %d was %02x, want %02x", i, got[i], want[i]);
    }
}

DEF_TEST(SkVM_Assembler, r) {
    // Easiest way to generate test cases is
    //
    //   echo '...some asm...' | llvm-mc -show-encoding -x86-asm-syntax=intel
    //
    // The -x86-asm-syntax=intel bit is optional, controlling the
    // input syntax only; the output will always be AT&T  op x,y,dst style.
    // Our APIs read more like Intel op dst,x,y as op(dst,x,y), so I find
    // that a bit easier to use here, despite maybe favoring AT&T overall.

    using A = skvm::Assembler;
    // Our exit strategy from AVX code.
    test_asm(r, [&](A& a) {
        a.vzeroupper();
        a.ret();
    },{
        0xc5, 0xf8, 0x77,
        0xc3,
    });

    // Align should pad with nop().
    test_asm(r, [&](A& a) {
        a.ret();
        a.align(4);
    },{
        0xc3,
        0x90, 0x90, 0x90,
    });

    test_asm(r, [&](A& a) {
        a.add(A::rax, 8);       // Always good to test rax.
        a.sub(A::rax, 32);

        a.add(A::rdi, 12);      // Last 0x48 REX
        a.sub(A::rdi, 8);

        a.add(A::r8 , 7);       // First 0x4c REX
        a.sub(A::r8 , 4);

        a.add(A::rsi, 128);     // Requires 4 byte immediate.
        a.sub(A::r8 , 1000000);
    },{
        0x48, 0x83, 0b11'000'000, 0x08,
        0x48, 0x83, 0b11'101'000, 0x20,

        0x48, 0x83, 0b11'000'111, 0x0c,
        0x48, 0x83, 0b11'101'111, 0x08,

        0x4c, 0x83, 0b11'000'000, 0x07,
        0x4c, 0x83, 0b11'101'000, 0x04,

        0x48, 0x81, 0b11'000'110, 0x80, 0x00, 0x00, 0x00,
        0x4c, 0x81, 0b11'101'000, 0x40, 0x42, 0x0f, 0x00,
    });


    test_asm(r, [&](A& a) {
        a.vpaddd (A::ymm0, A::ymm1, A::ymm2);  // Low registers and 0x0f map     -> 2-byte VEX.
        a.vpaddd (A::ymm8, A::ymm1, A::ymm2);  // A high dst register is ok      -> 2-byte VEX.
        a.vpaddd (A::ymm0, A::ymm8, A::ymm2);  // A high first argument register -> 2-byte VEX.
        a.vpaddd (A::ymm0, A::ymm1, A::ymm8);  // A high second argument         -> 3-byte VEX.
        a.vpmulld(A::ymm0, A::ymm1, A::ymm2);  // Using non-0x0f map instruction -> 3-byte VEX.
        a.vpsubd (A::ymm0, A::ymm1, A::ymm2);  // Test vpsubd to ensure argument order is right.
    },{
        /*    VEX     */ /*op*/ /*modRM*/
        0xc5,       0xf5, 0xfe, 0xc2,
        0xc5,       0x75, 0xfe, 0xc2,
        0xc5,       0xbd, 0xfe, 0xc2,
        0xc4, 0xc1, 0x75, 0xfe, 0xc0,
        0xc4, 0xe2, 0x75, 0x40, 0xc2,
        0xc5,       0xf5, 0xfa, 0xc2,
    });

    test_asm(r, [&](A& a) {
        a.vpsrld(A::ymm15, A::ymm2, 8);
        a.vpsrld(A::ymm0 , A::ymm8, 5);
    },{
        0xc5,     0x85, 0x72,0xd2, 0x08,
        0xc4,0xc1,0x7d, 0x72,0xd0, 0x05,
    });

    test_asm(r, [&](A& a) {
        a.vpermq(A::ymm1, A::ymm2, 5);
    },{
        0xc4,0xe3,0xfd, 0x00,0xca, 0x05,
    });

    test_asm(r, [&](A& a) {
        A::Label l = a.here();
        a.byte(1);
        a.byte(2);
        a.byte(3);
        a.byte(4);

        a.vbroadcastss(A::ymm0 , l);
        a.vbroadcastss(A::ymm1 , l);
        a.vbroadcastss(A::ymm8 , l);
        a.vbroadcastss(A::ymm15, l);

        a.vpshufb(A::ymm4, A::ymm3, l);
    },{
        0x01, 0x02, 0x03, 0x4,

        /*     VEX    */  /*op*/ /*   ModRM    */  /*     offset     */
        0xc4, 0xe2, 0x7d,  0x18,   0b00'000'101,   0xf3,0xff,0xff,0xff,   // 0xfffffff3 == -13
        0xc4, 0xe2, 0x7d,  0x18,   0b00'001'101,   0xea,0xff,0xff,0xff,   // 0xffffffea == -22
        0xc4, 0x62, 0x7d,  0x18,   0b00'000'101,   0xe1,0xff,0xff,0xff,   // 0xffffffe1 == -31
        0xc4, 0x62, 0x7d,  0x18,   0b00'111'101,   0xd8,0xff,0xff,0xff,   // 0xffffffd8 == -40

        0xc4, 0xe2, 0x65,  0x00,   0b00'100'101,   0xcf,0xff,0xff,0xff,   // 0xffffffcf == -49
    });

    test_asm(r, [&](A& a) {
        A::Label l = a.here();
        a.jne(l);
        for (int i = 0; i < 124; i++) {
            a.nop();
        }
        a.jne(l);
        a.jne(l);
    },{
        0x75, 0xfe,  // short jump -2 bytes

        0x90, 0x90, 0x90, 0x90, 0x90,  0x90, 0x90, 0x90, 0x90, 0x90,
        0x90, 0x90, 0x90, 0x90, 0x90,  0x90, 0x90, 0x90, 0x90, 0x90,
        0x90, 0x90, 0x90, 0x90, 0x90,  0x90, 0x90, 0x90, 0x90, 0x90,
        0x90, 0x90, 0x90, 0x90, 0x90,  0x90, 0x90, 0x90, 0x90, 0x90,

        0x90, 0x90, 0x90, 0x90, 0x90,  0x90, 0x90, 0x90, 0x90, 0x90,
        0x90, 0x90, 0x90, 0x90, 0x90,  0x90, 0x90, 0x90, 0x90, 0x90,
        0x90, 0x90, 0x90, 0x90, 0x90,  0x90, 0x90, 0x90, 0x90, 0x90,
        0x90, 0x90, 0x90, 0x90, 0x90,  0x90, 0x90, 0x90, 0x90, 0x90,

        0x90, 0x90, 0x90, 0x90, 0x90,  0x90, 0x90, 0x90, 0x90, 0x90,
        0x90, 0x90, 0x90, 0x90, 0x90,  0x90, 0x90, 0x90, 0x90, 0x90,
        0x90, 0x90, 0x90, 0x90, 0x90,  0x90, 0x90, 0x90, 0x90, 0x90,
        0x90, 0x90, 0x90, 0x90, 0x90,  0x90, 0x90, 0x90, 0x90, 0x90,

        0x90, 0x90, 0x90, 0x90,

        0x75, 0x80,                        // short jump -128 bytes
        0x0f, 0x85, 0x7a,0xff,0xff,0xff,   // near jump back -134 bytes
    });

    test_asm(r, [&](A& a) {
        a.vmovups(A::ymm5, A::rsi);
        a.vmovups(A::rsi, A::ymm5);

        a.vpmovzxbd(A::ymm4, A::rsi);

        a.vmovq(A::rdx, A::xmm15);
    },{
        /*    VEX    */  /*Op*/  /*  ModRM  */
        0xc5,     0xfc,   0x10,  0b00'101'110,
        0xc5,     0xfc,   0x11,  0b00'101'110,

        0xc4,0xe2,0x7d,   0x31,  0b00'100'110,

        0xc5,     0x79,   0xd6,  0b00'111'010,
    });

    test_asm(r, [&](A& a) {
        a.vpandn(A::ymm3, A::ymm12, A::ymm2);
    },{
        0xc5, 0x9d, 0xdf, 0xda,
    });

    // echo "fmul v4.4s, v3.4s, v1.4s" | llvm-mc -show-encoding -arch arm64

    test_asm(r, [&](A& a) {
        a.and16b(A::v4, A::v3, A::v1);
        a.orr16b(A::v4, A::v3, A::v1);
        a.eor16b(A::v4, A::v3, A::v1);
        a.bic16b(A::v4, A::v3, A::v1);

        a.add4s(A::v4, A::v3, A::v1);
        a.sub4s(A::v4, A::v3, A::v1);
        a.mul4s(A::v4, A::v3, A::v1);

        a.sub8h(A::v4, A::v3, A::v1);
        a.mul8h(A::v4, A::v3, A::v1);

        a.fadd4s(A::v4, A::v3, A::v1);
        a.fsub4s(A::v4, A::v3, A::v1);
        a.fmul4s(A::v4, A::v3, A::v1);
        a.fdiv4s(A::v4, A::v3, A::v1);

        a.fmla4s(A::v4, A::v3, A::v1);
    },{
        0x64,0x1c,0x21,0x4e,
        0x64,0x1c,0xa1,0x4e,
        0x64,0x1c,0x21,0x6e,
        0x64,0x1c,0x61,0x4e,

        0x64,0x84,0xa1,0x4e,
        0x64,0x84,0xa1,0x6e,
        0x64,0x9c,0xa1,0x4e,

        0x64,0x84,0x61,0x6e,
        0x64,0x9c,0x61,0x4e,

        0x64,0xd4,0x21,0x4e,
        0x64,0xd4,0xa1,0x4e,
        0x64,0xdc,0x21,0x6e,
        0x64,0xfc,0x21,0x6e,

        0x64,0xcc,0x21,0x4e,
    });

    test_asm(r, [&](A& a) {
        a.shl4s(A::v4, A::v3,  0);
        a.shl4s(A::v4, A::v3,  1);
        a.shl4s(A::v4, A::v3,  8);
        a.shl4s(A::v4, A::v3, 16);
        a.shl4s(A::v4, A::v3, 31);

        a.sshr4s(A::v4, A::v3,  1);
        a.sshr4s(A::v4, A::v3,  8);
        a.sshr4s(A::v4, A::v3, 31);

        a.ushr4s(A::v4, A::v3,  1);
        a.ushr4s(A::v4, A::v3,  8);
        a.ushr4s(A::v4, A::v3, 31);

        a.ushr8h(A::v4, A::v3,  1);
        a.ushr8h(A::v4, A::v3,  8);
        a.ushr8h(A::v4, A::v3, 15);
    },{
        0x64,0x54,0x20,0x4f,
        0x64,0x54,0x21,0x4f,
        0x64,0x54,0x28,0x4f,
        0x64,0x54,0x30,0x4f,
        0x64,0x54,0x3f,0x4f,

        0x64,0x04,0x3f,0x4f,
        0x64,0x04,0x38,0x4f,
        0x64,0x04,0x21,0x4f,

        0x64,0x04,0x3f,0x6f,
        0x64,0x04,0x38,0x6f,
        0x64,0x04,0x21,0x6f,

        0x64,0x04,0x1f,0x6f,
        0x64,0x04,0x18,0x6f,
        0x64,0x04,0x11,0x6f,
    });

    test_asm(r, [&](A& a) {
        a.scvtf4s (A::v4, A::v3);
        a.fcvtzs4s(A::v4, A::v3);
    },{
        0x64,0xd8,0x21,0x4e,
        0x64,0xb8,0xa1,0x4e,
    });

    test_asm(r, [&](A& a) {
        a.ret(A::x30);   // Conventional ret using link register.
        a.ret(A::x13);   // Can really return using any register if we like.

        a.add(A::x2, A::x2,  4);
        a.add(A::x3, A::x2, 32);

        a.sub(A::x2, A::x2, 4);
        a.sub(A::x3, A::x2, 32);

        a.subs(A::x2, A::x2,  4);
        a.subs(A::x3, A::x2, 32);

        a.subs(A::xzr, A::x2, 4);  // These are actually the same instruction!
        a.cmp(A::x2, 4);

        A::Label l = a.here();
        a.bne(l);
        a.bne(l);
        a.blt(l);
        a.b(l);
        a.cbnz(A::x2, l);
        a.cbz(A::x2, l);
    },{
        0xc0,0x03,0x5f,0xd6,
        0xa0,0x01,0x5f,0xd6,

        0x42,0x10,0x00,0x91,
        0x43,0x80,0x00,0x91,

        0x42,0x10,0x00,0xd1,
        0x43,0x80,0x00,0xd1,

        0x42,0x10,0x00,0xf1,
        0x43,0x80,0x00,0xf1,

        0x5f,0x10,0x00,0xf1,
        0x5f,0x10,0x00,0xf1,

        0x01,0x00,0x00,0x54,   // b.ne #0
        0xe1,0xff,0xff,0x54,   // b.ne #-4
        0xcb,0xff,0xff,0x54,   // b.lt #-8
        0xae,0xff,0xff,0x54,   // b.al #-12
        0x82,0xff,0xff,0xb5,   // cbnz x2, #-16
        0x62,0xff,0xff,0xb4,   // cbz x2, #-20
    });

    test_asm(r, [&](A& a) {
        a.ldrq(A::v0, A::x8);
        a.strq(A::v0, A::x8);
    },{
        0x00,0x01,0xc0,0x3d,
        0x00,0x01,0x80,0x3d,
    });

    test_asm(r, [&](A& a) {
        a.xtns2h(A::v0, A::v0);
        a.xtnh2b(A::v0, A::v0);
        a.strs  (A::v0, A::x0);

        a.ldrs   (A::v0, A::x0);
        a.uxtlb2h(A::v0, A::v0);
        a.uxtlh2s(A::v0, A::v0);
    },{
        0x00,0x28,0x61,0x0e,
        0x00,0x28,0x21,0x0e,
        0x00,0x00,0x00,0xbd,

        0x00,0x00,0x40,0xbd,
        0x00,0xa4,0x08,0x2f,
        0x00,0xa4,0x10,0x2f,
    });

    test_asm(r, [&](A& a) {
        a.ldrb(A::v0, A::x8);
        a.strb(A::v0, A::x8);
    },{
        0x00,0x01,0x40,0x3d,
        0x00,0x01,0x00,0x3d,
    });
}