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Avoid a separate 0 register in VecAdd64 and VecSub64

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Jeffrey Walton 2020-04-08 07:07:28 -04:00
parent 64bf2ec38e
commit d3c3b579ba
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GPG Key ID: B36AB348921B1838
1 changed files with 18 additions and 12 deletions
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30
ppc_simd.h
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@ -1893,14 +1893,17 @@ inline uint32x4_p VecAdd64(const uint32x4_p& vec1, const uint32x4_p& vec2)
#if defined(_ARCH_PWR8)
return (uint32x4_p)vec_add((uint64x2_p)vec1, (uint64x2_p)vec2);
#else
// The carry mask selects carries for elements 1 and 3 and sets remaining
// elements to 0. The mask also shifts the carried values left by 4 bytes
// so the carries are added to elements 0 and 2.
const uint8x16_p cmask = {4,5,6,7, 16,16,16,16, 12,13,14,15, 16,16,16,16};
const uint32x4_p zero = {0, 0, 0, 0};
// The carry mask selects carries for elements 1 and 3 and sets
// remaining elements to 0. The mask also shifts the carried values
// left by 4 bytes so the carries are added to elements 0 and 2.
// Small optimization to avoid the load of a 'zero' value: only bytes
// 3, 7, 11 or 15 have a 1 set due to carry. Other bytes will be zero,
// so we don't need a separate zero value to draw from.
const uint8x16_p cmask = {4,5,6,7, 0,0,0,0, 12,13,14,15, 0,0,0,0};
uint32x4_p cy = vec_addc(vec1, vec2);
cy = vec_perm(cy, zero, cmask);
cy = vec_perm(cy, cy, cmask);
return vec_add(vec_add(vec1, vec2), cy);
#endif
}
@ -1938,17 +1941,20 @@ inline uint32x4_p VecSub64(const uint32x4_p& vec1, const uint32x4_p& vec2)
// 64-bit elements available at POWER7 with VSX, but subudm requires POWER8
return (uint32x4_p)vec_sub((uint64x2_p)vec1, (uint64x2_p)vec2);
#else
// The borrow mask selects borrows for elements 1 and 3 and sets remaining
// elements to 0. The mask also shifts the borrowed values left by 4 bytes
// so the borrows are subtracted from elements 0 and 2.
const uint8x16_p bmask = {4,5,6,7, 16,16,16,16, 12,13,14,15, 16,16,16,16};
// The borrow mask selects borrows for elements 1 and 3 and sets
// remaining elements to 0. The mask also shifts the borrowed values
// left by 4 bytes so the borrows are subtracted from elements 0 and 2.
// Small optimization to avoid the load of a 'zero' value: only bytes
// 3, 7, 11 or 15 have a 1 set due to borrow. Other bytes will be zero,
// so we don't need a separate zero value to draw from.
const uint8x16_p bmask = {4,5,6,7, 0,0,0,0, 12,13,14,15, 0,0,0,0};
const uint32x4_p amask = {1, 1, 1, 1};
const uint32x4_p zero = {0, 0, 0, 0};
// subc sets the compliment of borrow, so we have to un-compliment it using andc.
uint32x4_p bw = vec_subc(vec1, vec2);
bw = vec_andc(amask, bw);
bw = vec_perm(bw, zero, bmask);
bw = vec_perm(bw, bw, bmask);
return vec_sub(vec_sub(vec1, vec2), bw);
#endif
}