microw8/platform/src/ges.cwa

const GesChannelState.Trigger = 0;
const GesChannelState.EnvState = 1;
const GesChannelState.EnvVol = 2;
const GesChannelState.Phase = 4;
const GesChannelState.Size = 6;

const GesState.Filter = GesChannelState.Size * 4;
const GesState.Size = GesState.Filter + 8*4;

const GesStateOffset = 112;
const GesBufferOffset = 112 + GesState.Size;

export fn gesSnd(t: i32) -> f32 {
    if !(t & 127) {
        let i: i32;
        loop clearLoop {
            i!GesBufferOffset = 0;
            branch_if (i := i + 4) < 128*8: clearLoop;
        }

        let ch: i32;
        loop channelLoop {
            let lazy channelState = GesStateOffset + ch * GesChannelState.Size;
            let lazy channelReg = 80 + ch * 6;
            let envState = channelState?GesChannelState.EnvState;
            let envVol = i32.load16_u(channelState, GesChannelState.EnvVol);

            let lazy oldTrigger = channelState?GesChannelState.Trigger;
            let lazy ctrl = channelReg?0;
            if (oldTrigger ^ ctrl) & (ctrl | 2) & 3 {
                envState = 1;
                envVol = 0;
            }
            channelState?GesChannelState.Trigger = ctrl;

            if envState {
                let lazy attack = channelReg?4 & 15;
                envVol = envVol + 12 * pow(1.5625, (15 - attack) as f32) as i32;
                if envVol >= 65535 | !attack {
                    envVol = 65535;
                    envState = 0;
                }
            } else {
                let inline decay = (channelReg - (ctrl & 1))?5 >> 4;
                let inline dec = 8 * pow(1.5625, (15 - decay) as f32) as i32;
                envVol = envVol - ((dec * (envVol + 8192)) >> 16);
                let inline sustain = (channelReg?5 & 15) << 12;
                let lazy targetVol = (ctrl & 1) * sustain;
                if envVol < targetVol {
                    envVol = targetVol;
                }
            }
            channelState?GesChannelState.EnvState = envState;

            i32.store16(envVol, channelState, GesChannelState.EnvVol);

            let inline note = i32.load16_u(channelReg, 2);
            let inline freq = 440 as f32 * pow(2.0, (note - 69*256) as f32 / (12*256) as f32);
            let phaseInc = (freq * (65536.0 / 44100.0)) as i32;

            let phase = i32.load16_u(channelState, GesChannelState.Phase) << 8;

            let inline pulseWidth = channelReg?1;
            let phaseShift = (pulseWidth - 128) * 255;
            let invPhaseInc = 1 as f32 / phaseInc as f32;

            i = 0;
            let wave = ctrl >> 6;
            if wave < 2 {
                if wave {
                    let pulsePhase1 = pulseWidth << 23;
                    let pulsePhase2 = (511 - pulseWidth) << 23;
                    loop sawLoop {
                        let p = (phase ^ 32768) << 16;
                        let saw = (p >> 16) - polyBlep(phase, invPhaseInc, -32767);
                        let saw2 = select(p #>= pulsePhase1 & p #< pulsePhase2, -saw, saw);
                        let saw2 = saw2 -
                            polyBlep((p - pulsePhase1) >> 16, invPhaseInc, -saw) -
                            polyBlep((p - pulsePhase2) >> 16, invPhaseInc, saw);
                        i!(GesBufferOffset + 128*4) = saw2;
                        phase = phase + phaseInc;
                        branch_if (i := i + 4) < 64*4: sawLoop;
                    }
                }
                else
                {
                    let pulsePhase = 32768 + pulseWidth * 128;
                    loop rectLoop {
                        i!(GesBufferOffset + 128*4) = select((phase & 65535) < pulsePhase, -32768, 32767) -
                            polyBlep(phase, invPhaseInc, -32767) -
                            polyBlep(phase - pulsePhase, invPhaseInc, 32767);
                        phase = phase + phaseInc;
                        branch_if (i := i + 4) < 64*4: rectLoop;
                    }
                }
            } else {
                if wave == 2 {
                    let scale = pulseWidth + 256;
                    loop triLoop {
                        let s = phase << 16;
                        s = (s ^ (s >> 31));
                        s = (s >> 8) * scale;
                        s = (s ^ (s >> 31));
                        i!(GesBufferOffset + 128*4) = (s >> 15) - 32768;
                        phase = phase + phaseInc;
                        branch_if (i := i + 4) < 64*4: triLoop;
                    }
                } else {
                    loop noiseLoop {
                        let s = (phase >> 12) & 4095;
                        let pulse = ((phase >> 8) & 255) >= pulseWidth;
                        s = s * 0x6746ba73;
                        s = s ^ (s >> 15) * pulse;
                        i!(GesBufferOffset + 128*4) = (s * 0x83567a92 + (phase << 16)) >> 16;
                        phase = phase + phaseInc;
                        branch_if (i := i + 4) < 64*4: noiseLoop;
                    }
                }
            }

            i32.store16(phase >> 8, channelState, GesChannelState.Phase);

            let channelVol = ((ch >> 1)?0x68 >> ((ch & 1) * 4)) & 15;
            envVol = envVol * channelVol / 15;

            let leftVol = (0x4c6a >> (ch * 4)) & 15;
            let rightVol = 16 - leftVol;

            let lazy filter = ((ctrl >> 2) & 3) - 1;

            i = 0;
            if filter #> 1 {
                loop mixLoop {
                    let sample = (i!(GesBufferOffset + 128*4) * envVol) >> 18;
                    (i * 2)!GesBufferOffset = (i * 2)!GesBufferOffset + ((sample * leftVol) >> 4);
                    (i * 2)!(GesBufferOffset + 4) = (i * 2)!(GesBufferOffset + 4) + ((sample * rightVol) >> 4);
                    branch_if (i := i + 4) < 64*4: mixLoop;
                }
            } else {
                let ctrl = filter?0x6a;
                let note = i32.load16_u(filter * 2, 0x6c);
                let inline freq = 440 as f32 * pow(2.0, (note - 69*256) as f32 / (12*256) as f32);
                let F = (8192 as f32 * sin(min(0.25, freq / 44100 as f32) * 3.1415)) as i32;
                let Q = 8192 - (ctrl >> 4) * (7000/15);
                let Qlimit = (8192*4096/F - F/2) * 3 / 4;
                if Q > Qlimit {
                    Q = Qlimit;
                }
                let low_out = ctrl & 1;
                let high_out = (ctrl >> 1) & 1;
                let band_out = (ctrl >> 2) & 1;
                let low = (ch * 8)!(GesStateOffset + GesState.Filter);
                let band = (ch * 8)!(GesStateOffset + GesState.Filter + 4);
                loop filterLoop {
                    let in = (i!(GesBufferOffset + 128*4) * envVol) >> 18;

                    let high = in - low - ((band * Q) >> 12);
                    band = band + ((F * high) >> 12);
                    low = low + ((F * band) >> 12);

                    let sample = low * low_out + high * high_out + band * band_out;
                    (i * 2)!GesBufferOffset = (i * 2)!GesBufferOffset + ((sample * leftVol) >> 4);
                    (i * 2)!(GesBufferOffset + 4) = (i * 2)!(GesBufferOffset + 4) + ((sample * rightVol) >> 4);
                    branch_if (i := i + 4) < 64*4: filterLoop;
                }
                (ch * 8)!(GesStateOffset + GesState.Filter) = low;
                (ch * 8)!(GesStateOffset + GesState.Filter + 4) = band;
            }

            branch_if (ch := ch + 1) < 4: channelLoop;
        }
    }
    (((t & 127) * 4)!GesBufferOffset) as f32 / 32768 as f32
}

fn polyBlep(transientPhase: i32, invPhaseInc: f32, magnitude: i32) -> i32 {
    let lazy t = ((transientPhase << 16) >> 16) as f32 * invPhaseInc;
    let lazy x = max(0 as f32, 1 as f32 - abs(t));
    (f32.copysign(x * x, t) * magnitude as f32) as i32
}