mirror of
https://github.com/n64dev/cen64.git
synced 2025-04-02 10:31:54 -04:00
7262516636
No need to separate all these functions when they contain so much common code, so start combining things for the sake of locality and predictor effectiveness (and size). In addition to these benefits, the CPU backend is usually busy during the execution of these functions, so suffering a misprediction isn't as painful (especially seeing as we can potentially improve the prediction from the indirect branch).
66 lines
2 KiB
C
66 lines
2 KiB
C
//
|
|
// arch/x86_64/rsp/vmulm.h
|
|
//
|
|
// This file is subject to the terms and conditions defined in
|
|
// 'LICENSE', which is part of this source code package.
|
|
//
|
|
|
|
#include "common.h"
|
|
|
|
static inline __m128i rsp_vmadm_vmudm(uint32_t iw, __m128i vs, __m128i vt,
|
|
__m128i zero, __m128i *acc_lo, __m128i *acc_md, __m128i *acc_hi) {
|
|
__m128i lo, hi, sign, overflow_mask;
|
|
|
|
lo = _mm_mullo_epi16(vs, vt);
|
|
hi = _mm_mulhi_epu16(vs, vt);
|
|
|
|
// What we're really want to do is unsigned vs * signed vt.
|
|
// However, we have no such instructions to do so.
|
|
//
|
|
// There's a trick to "fix" an unsigned product, though:
|
|
// If vt was negative, take the upper 16-bits of the product
|
|
// and subtract vs.
|
|
sign = _mm_srai_epi16(vs, 15);
|
|
vt = _mm_and_si128(vt, sign);
|
|
hi = _mm_sub_epi16(hi, vt);
|
|
|
|
// VMADM
|
|
if (iw & 0x8) {
|
|
// Tricky part: start accumulate everything.
|
|
// Get/keep the carry as we'll add it in later.
|
|
overflow_mask = _mm_adds_epu16(*acc_lo, lo);
|
|
*acc_lo = _mm_add_epi16(*acc_lo, lo);
|
|
|
|
overflow_mask = _mm_cmpeq_epi16(*acc_lo, overflow_mask);
|
|
overflow_mask = _mm_cmpeq_epi16(overflow_mask, zero);
|
|
|
|
// This is REALLY clever. Since the product results from
|
|
// two 16-bit components, one positive and one negative,
|
|
// we don't have to worry about carrying the 1 (we can
|
|
// only borrow) past 32-bits. So we can just add it here.
|
|
hi = _mm_sub_epi16(hi, overflow_mask);
|
|
|
|
// Check for overflow of the upper sum.
|
|
overflow_mask = _mm_adds_epu16(*acc_md, hi);
|
|
*acc_md = _mm_add_epi16(*acc_md, hi);
|
|
|
|
overflow_mask = _mm_cmpeq_epi16(*acc_md, overflow_mask);
|
|
overflow_mask = _mm_cmpeq_epi16(overflow_mask, zero);
|
|
|
|
// Finish up the accumulation of the... accumulator.
|
|
*acc_hi = _mm_add_epi16(*acc_hi, _mm_srai_epi16(hi, 15));
|
|
*acc_hi = _mm_sub_epi16(*acc_hi, overflow_mask);
|
|
|
|
return rsp_sclamp_acc_tomd(*acc_md, *acc_hi);
|
|
}
|
|
|
|
// VMUDM
|
|
else {
|
|
*acc_lo = lo;
|
|
*acc_md = hi;
|
|
*acc_hi = _mm_srai_epi16(hi, 15);
|
|
|
|
return hi;
|
|
}
|
|
}
|
|
|