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SPU: Pack reverb FIR coefficients into 16-bit lanes

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Use three packed multiply-adds for the 20-tap upsampling FIR and widen
the shared coefficients for downsampling. Preserve the final shift and clamp.
The absolute coefficient sum is 31142, keeping every s32 sum within range.

Validated output, persistent state, and RAM against the original across
8,192 frames using both SSE4.1 and SSE2; compiled with clang-cl /O2.
This commit is contained in:
Stenzek
2026-10-10 21:47:42 +10:00
parent e7098b5156
commit aad9c4ebec
1 changed files with 20 additions and 19 deletions
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src/core/spu.cpp
+20 -19
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@@ -2279,7 +2279,7 @@ void SPU::ProcessReverb(s32 left_in, s32 right_in, s32* left_out, s32* right_out
//
// Zeros have been removed since the result is always zero, therefore the multiply is redundant.
alignas(VECTOR_ALIGNMENT) static constexpr std::array<s32, 20> resample_coeff = {
alignas(VECTOR_ALIGNMENT) static constexpr std::array<s16, 20> resample_coeff = {
-0x0001, 0x0002, -0x000A, 0x0023, -0x0067, 0x010A, -0x0268, 0x0534, -0x0B90, 0x2806,
0x2806, -0x0B90, 0x0534, -0x0268, 0x010A, -0x0067, 0x0023, -0x000A, 0x0002, -0x0001};
@@ -2310,16 +2310,21 @@ void SPU::ProcessReverb(s32 left_in, s32 right_in, s32* left_out, s32* right_out
{
const s16* src =
&s_state.reverb_downsample_buffer[channel][(s_state.reverb_resample_buffer_position - 38) & 0x3F];
GSVector4i acc =
GSVector4i::load<true>(&resample_coeff[0]).mul32l(GSVector4i::load<false>(&src[0]).sll32(16).sra32(16));
acc = acc.add32(
GSVector4i::load<true>(&resample_coeff[4]).mul32l(GSVector4i::load<false>(&src[8]).sll32(16).sra32(16)));
acc = acc.add32(
GSVector4i::load<true>(&resample_coeff[8]).mul32l(GSVector4i::load<false>(&src[16]).sll32(16).sra32(16)));
acc = acc.add32(
GSVector4i::load<true>(&resample_coeff[12]).mul32l(GSVector4i::load<false>(&src[24]).sll32(16).sra32(16)));
acc = acc.add32(
GSVector4i::load<true>(&resample_coeff[16]).mul32l(GSVector4i::load<false>(&src[32]).sll32(16).sra32(16)));
GSVector4i acc = GSVector4i::loadl<true>(&resample_coeff[0])
.s16to32()
.mul32l(GSVector4i::load<false>(&src[0]).sll32(16).sra32(16));
acc = acc.add32(GSVector4i::loadl<true>(&resample_coeff[4])
.s16to32()
.mul32l(GSVector4i::load<false>(&src[8]).sll32(16).sra32(16)));
acc = acc.add32(GSVector4i::loadl<true>(&resample_coeff[8])
.s16to32()
.mul32l(GSVector4i::load<false>(&src[16]).sll32(16).sra32(16)));
acc = acc.add32(GSVector4i::loadl<true>(&resample_coeff[12])
.s16to32()
.mul32l(GSVector4i::load<false>(&src[24]).sll32(16).sra32(16)));
acc = acc.add32(GSVector4i::loadl<true>(&resample_coeff[16])
.s16to32()
.mul32l(GSVector4i::load<false>(&src[32]).sll32(16).sra32(16)));
// Horizontal reduction, middle 0x4000. Moved here so we don't need another 4 elements above.
downsampled[channel] = Clamp16((acc.addv_s32() + (0x4000 * src[19])) >> 15);
@@ -2398,14 +2403,10 @@ void SPU::ProcessReverb(s32 left_in, s32 right_in, s32* left_out, s32* right_out
const s16* src =
&s_state.reverb_upsample_buffer[channel][((s_state.reverb_resample_buffer_position >> 1) - 19) & 0x1F];
GSVector4i srcs = GSVector4i::load<false>(&src[0]);
GSVector4i acc = GSVector4i::load<true>(&resample_coeff[0]).mul32l(srcs.s16to32());
acc = acc.add32(GSVector4i::load<true>(&resample_coeff[4]).mul32l(srcs.uph64().s16to32()));
srcs = GSVector4i::load<false>(&src[8]);
acc = acc.add32(GSVector4i::load<true>(&resample_coeff[8]).mul32l(srcs.s16to32()));
acc = acc.add32(GSVector4i::load<true>(&resample_coeff[12]).mul32l(srcs.uph64().s16to32()));
srcs = GSVector4i::loadl<false>(&src[16]);
acc = acc.add32(GSVector4i::load<true>(&resample_coeff[16]).mul32l(srcs.s16to32()));
// The absolute coefficient sum is 31142, so s32 accumulation cannot overflow.
GSVector4i acc = GSVector4i::load<false>(&src[0]).madd_s16(GSVector4i::load<true>(&resample_coeff[0]));
acc = acc.add32(GSVector4i::load<false>(&src[8]).madd_s16(GSVector4i::load<true>(&resample_coeff[8])));
acc = acc.add32(GSVector4i::loadl<false>(&src[16]).madd_s16(GSVector4i::loadl<true>(&resample_coeff[16])));
out[channel] = std::clamp<s32>(acc.addv_s32() >> 14, -32768, 32767);
}