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authorMitja Felicijan <mitja.felicijan@gmail.com>2026-02-12 20:57:17 +0100
committerMitja Felicijan <mitja.felicijan@gmail.com>2026-02-12 20:57:17 +0100
commitb333b06772c89d96aacb5490d6a219fba7c09cc6 (patch)
tree211df60083a5946baa2ed61d33d8121b7e251b06 /llama.cpp/ggml/src/ggml-hexagon/htp/hvx-inverse.h
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+#ifndef HVX_INVERSE_H
+#define HVX_INVERSE_H
+
+#include <HAP_farf.h>
+
+#include <math.h>
+#include <string.h>
+#include <assert.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "hvx-base.h"
+
+// ====================================================
+// FUNCTION: 1/(x+1) y(0) = 1, y(0.5) = 0.6667, y(1) = 0.5
+// Order:3; continuity: True; Ends forced: True
+// Mode: unsigned; Result fractional bits: 14
+// Peak Error: 1.1295e-04 Rms Error: 2.8410e-05 Mean Error: 1.1370e-05
+// 32769 -32706 31252 -10589
+// 32590 -30635 22793 -4493
+// 32066 -27505 16481 -2348
+// 31205 -24054 11849 -1306
+
+static inline HVX_Vector hvx_vec_recip_xp1_O3_unsigned(HVX_Vector vx) {
+ // input is 0..0xffff representing 0.0 .. 1.0
+ HVX_Vector p;
+ p = Q6_Vh_vlut4_VuhPh(vx, 0xFAE6F6D4EE73D6A3ull);
+ p = Q6_Vh_vmpa_VhVhVuhPuh_sat(p, vx, 0x2E49406159097A14ull);
+ p = Q6_Vh_vmps_VhVhVuhPuh_sat(p, vx, 0x5DF66B7177AB7FC2ull);
+ p = Q6_Vh_vmpa_VhVhVuhPuh_sat(p, vx, 0x79E57D427F4E8001ull);
+ return p; // signed result, 14 fractional bits
+}
+
+// Find reciprocal of fp16.
+// (1) first, convert to fp32, multiplying by 1.0; this is done to
+// handle denormals. Ignoring sign and zero, result should be at
+// least 5.9604645e-08 (32-bit code 0x33800000) and at most 131008 (0x47ffe000)
+// (exponent in range [103,143])
+// (2) extract the mantissa into 16-bit unsigned; find reciprocal using a fitted poly
+// (3) put this, along with '253-exp' (exp from (1)) together to make an qf32
+// (4) convert that to fp16
+// (5) put sign back in. Also, if the original value (w/o sign) was <0x81, replace
+// the result with the max value.
+static inline HVX_Vector hvx_vec_inverse_f16(HVX_Vector vals) {
+ HVX_Vector em_mask = Q6_Vh_vsplat_R(0x7FFF);
+ HVX_Vector avals = Q6_V_vand_VV(vals, em_mask);
+ HVX_VectorPred is_neg = Q6_Q_vcmp_gt_VhVh(avals, vals);
+ // is too small to 1/x ? for 'standard' fp16, this would be 0x101
+ HVX_VectorPred is_small = Q6_Q_vcmp_gt_VhVh(Q6_Vh_vsplat_R(0x101), avals);
+
+ HVX_VectorPair to_qf32 = Q6_Wqf32_vmpy_VhfVhf(avals, Q6_Vh_vsplat_R(0x3C00)); // *1.0
+ HVX_Vector to_f32_0 = Q6_Vsf_equals_Vqf32(Q6_V_lo_W(to_qf32));
+ HVX_Vector to_f32_1 = Q6_Vsf_equals_Vqf32(Q6_V_hi_W(to_qf32));
+
+ // bits 22..13 contain the mantissa now (w/o hidden bit); move to bit 14..5 of a 16-bit vector
+ HVX_Vector mant_u16 = Q6_Vh_vshuffo_VhVh(Q6_Vw_vasl_VwR(to_f32_1, 9), Q6_Vw_vasl_VwR(to_f32_0, 9));
+ // likewise extract the upper 16 from each, containing the exponents in range 103..142
+ HVX_Vector exp_u16 = Q6_Vh_vshuffo_VhVh(to_f32_1, to_f32_0);
+ //Get exponent in IEEE 32-bit representation
+ exp_u16 = Q6_Vuh_vlsr_VuhR(exp_u16, 7);
+
+ // so, mant_u16 contains an unbiased mantissa in upper 10 bits of each u16 lane
+ // We can consider it to be x-1.0, with 16 fractional bits, where 'x' is in range [1.0,2.0)
+ // Use poly to transform to 1/x, with 14 fractional bits
+ //
+ HVX_Vector rm = hvx_vec_recip_xp1_O3_unsigned(mant_u16);
+
+ HVX_Vector vcl0 = Q6_Vuh_vcl0_Vuh(rm); //count leading zeros
+
+ // Get mantissa for 16-bit represenation
+ HVX_Vector mant_recip = Q6_V_vand_VV(Q6_Vh_vasr_VhR(Q6_Vh_vasl_VhVh(rm, vcl0), 5), Q6_Vh_vsplat_R(0x03FF));
+
+ //Compute Reciprocal Exponent
+ HVX_Vector exp_recip =
+ Q6_Vh_vsub_VhVh(Q6_Vh_vsub_VhVh(Q6_Vh_vsplat_R(254), exp_u16), Q6_Vh_vsub_VhVh(vcl0, Q6_Vh_vsplat_R(1)));
+ //Convert it for 16-bit representation
+ exp_recip = Q6_Vh_vadd_VhVh_sat(Q6_Vh_vsub_VhVh(exp_recip, Q6_Vh_vsplat_R(127)), Q6_Vh_vsplat_R(15));
+ exp_recip = Q6_Vh_vasl_VhR(exp_recip, 10);
+
+ //Merge exponent and mantissa for reciprocal
+ HVX_Vector recip = Q6_V_vor_VV(exp_recip, mant_recip);
+ // map 'small' inputs to standard largest value 0x7bff
+ recip = Q6_V_vmux_QVV(is_small, Q6_Vh_vsplat_R(0x7bff), recip);
+ // add sign back
+ recip = Q6_V_vandor_VQR(recip, is_neg, 0x80008000);
+ return recip;
+}
+
+static inline HVX_Vector hvx_vec_inverse_f32(HVX_Vector v_sf) {
+ HVX_Vector inv_aprox_sf = Q6_V_vsplat_R(0x7EEEEBB3);
+ HVX_Vector two_sf = hvx_vec_splat_f32(2.0);
+
+ // First approximation
+ HVX_Vector i_sf = Q6_Vw_vsub_VwVw(inv_aprox_sf, v_sf);
+
+ HVX_Vector r_qf;
+
+ // Refine
+ r_qf = Q6_Vqf32_vmpy_VsfVsf(
+ i_sf, Q6_Vsf_equals_Vqf32(Q6_Vqf32_vsub_VsfVsf(two_sf, Q6_Vsf_equals_Vqf32(Q6_Vqf32_vmpy_VsfVsf(i_sf, v_sf)))));
+ r_qf = Q6_Vqf32_vmpy_Vqf32Vqf32(
+ r_qf, Q6_Vqf32_vsub_VsfVsf(two_sf, Q6_Vsf_equals_Vqf32(Q6_Vqf32_vmpy_VsfVsf(Q6_Vsf_equals_Vqf32(r_qf), v_sf))));
+ r_qf = Q6_Vqf32_vmpy_Vqf32Vqf32(
+ r_qf, Q6_Vqf32_vsub_VsfVsf(two_sf, Q6_Vsf_equals_Vqf32(Q6_Vqf32_vmpy_VsfVsf(Q6_Vsf_equals_Vqf32(r_qf), v_sf))));
+
+ return Q6_Vsf_equals_Vqf32(r_qf);
+}
+
+static inline HVX_Vector hvx_vec_inverse_f32_guard(HVX_Vector v_sf, HVX_Vector nan_inf_mask) {
+ HVX_Vector out = hvx_vec_inverse_f32(v_sf);
+
+ HVX_Vector masked_out = Q6_V_vand_VV(out, nan_inf_mask);
+ const HVX_VectorPred pred = Q6_Q_vcmp_eq_VwVw(nan_inf_mask, masked_out);
+
+ return Q6_V_vmux_QVV(pred, Q6_V_vzero(), out);
+}
+
+#define hvx_inverse_f32_loop_body(dst_type, src_type, vec_store) \
+ do { \
+ dst_type * restrict vdst = (dst_type *) dst; \
+ src_type * restrict vsrc = (src_type *) src; \
+ \
+ const HVX_Vector nan_inf_mask = Q6_V_vsplat_R(0x7f800000); \
+ \
+ const uint32_t nvec = n / VLEN_FP32; \
+ const uint32_t nloe = n % VLEN_FP32; \
+ \
+ uint32_t i = 0; \
+ \
+ _Pragma("unroll(4)") \
+ for (; i < nvec; i++) { \
+ vdst[i] = hvx_vec_inverse_f32_guard(vsrc[i], nan_inf_mask); \
+ } \
+ if (nloe) { \
+ HVX_Vector v = hvx_vec_inverse_f32_guard(vsrc[i], nan_inf_mask); \
+ vec_store((void *) &vdst[i], nloe * SIZEOF_FP32, v); \
+ } \
+ } while(0)
+
+static inline void hvx_inverse_f32_aa(uint8_t * restrict dst, const uint8_t * restrict src, uint32_t n) {
+ assert((unsigned long) dst % 128 == 0);
+ assert((unsigned long) src % 128 == 0);
+ hvx_inverse_f32_loop_body(HVX_Vector, HVX_Vector, hvx_vec_store_a);
+}
+
+static inline void hvx_inverse_f32_au(uint8_t * restrict dst, const uint8_t * restrict src, uint32_t n) {
+ assert((unsigned long) dst % 128 == 0);
+ hvx_inverse_f32_loop_body(HVX_Vector, HVX_UVector, hvx_vec_store_a);
+}
+
+static inline void hvx_inverse_f32_ua(uint8_t * restrict dst, const uint8_t * restrict src, uint32_t n) {
+ assert((unsigned long) src % 128 == 0);
+ hvx_inverse_f32_loop_body(HVX_UVector, HVX_Vector, hvx_vec_store_u);
+}
+
+static inline void hvx_inverse_f32_uu(uint8_t * restrict dst, const uint8_t * restrict src, uint32_t n) {
+ hvx_inverse_f32_loop_body(HVX_UVector, HVX_UVector, hvx_vec_store_u);
+}
+
+static inline void hvx_inverse_f32(uint8_t * restrict dst, uint8_t * restrict src, const int num_elems) {
+ if ((unsigned long) dst % 128 == 0) {
+ if ((unsigned long) src % 128 == 0) {
+ hvx_inverse_f32_aa(dst, src, num_elems);
+ } else {
+ hvx_inverse_f32_au(dst, src, num_elems);
+ }
+ } else {
+ if ((unsigned long) src % 128 == 0) {
+ hvx_inverse_f32_ua(dst, src, num_elems);
+ } else {
+ hvx_inverse_f32_uu(dst, src, num_elems);
+ }
+ }
+}
+
+#endif // HVX_INVERSE_H