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IN NO EVENT SHALL THE COPYRIGHT OWNER OR */ /* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, */ /* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT */ /* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; */ /* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) */ /* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN */ /* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR */ /* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, */ /* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /* -------------------------------------------------------------- */ /* PROLOG END TAG zYx */ #ifdef __SPU__ #ifndef _DIVF4_H_ #define _DIVF4_H_ 1 #include /* * FUNCTION * vector float _divf4(vector float dividend, vector float divisor) * * DESCRIPTION * The _divf4 function divides the vector dividend by the vector divisor * and returns the resulting vector quotient. * */ static __inline vector float _divf4(vector float a, vector float b) { /* This function has been designed to provide a * full function operation that presisely computes * the quotient for the entire range of extended * single precision inputs and . This includes: * * 1) Computing the quotient to full single precision * floating point accuracy. * 2) Round the result consistently with the rounding * mode of the processor - truncated toward zero. * 3) Underflow and overflow results are clamped to * Smin and Smax and flagged with the appropriate * UNF or OVF exception in the FPSCR. * 4) Divide By Zero (DBZ) exception is produced when * the divisor has a zero exponent. A quotient * of correctly signed Smax is produced. * 5) Denorm/zero divided by a denorm/zero generates * a DBZ with the results undefined. * 6) Resulting denorm quotients will be coerced to +0. * 7) If a non-compliant IEEE result is produced, the * a DIFF exception is generated. */ vector float inv_b, err, q0, q1, q2; vector float mult; vector float mant_a, mant_b; vector float one = spu_splats(1.0f); vector unsigned int exp, exp_a, exp_b, overflow; vector unsigned int exp_mask = (vec_uint4)spu_splats(0x7F800000); /* If b has a zero exponent, then set the divide by zero * (DBZ) exception flag. The estimate result is discarded. * Note: This must be implemented as inline assembly. Otherwise * the optimizer removes it. */ (void)si_frest((qword)(b)); /* For computing the quotient, force the divisor and * dividend into the range (1.0 <= 0 < 2.0). */ mant_a = spu_sel(a, one, exp_mask); mant_b = spu_sel(b, one, exp_mask); /* Compute the quotient using reciprocal estimate * followed by one iteration of the Newton-Raphson. */ inv_b = spu_re(mant_b); q0 = spu_mul(mant_a, inv_b); q1 = spu_nmsub(mant_b, q0, mant_a); q1 = spu_madd(inv_b, q1, q0); /* Due to truncation error, the quotient result * may be low by 1 ulp (unit of least position), * Conditionally add one if the estimate is too * small. */ q2 = (vector float)spu_add((vector unsigned int)(q1), 1); err = spu_nmsub(mant_b, q2, mant_a); q2 = spu_sel(q1, q2, spu_cmpgt((vector signed int)err, -1)); /* Compute the quotient's expected exponent. If the exponent * is out of range, then force the resulting exponent to 0. * (127 with the bias). We correct for the out of range * values by computing a multiplier (mult) that will force the * result to the correct out of range value and set the * correct exception flag (UNF, OVF, or neither). The multiplier * is also conditioned to generate correctly signed Smax if the * divisor b is a denorm or zero. */ exp_a = spu_and((vector unsigned int)a, exp_mask); exp_b = spu_and((vector unsigned int)b, exp_mask); exp = spu_add(spu_sub(spu_add(exp_a, (vector unsigned int)one), exp_b), spu_cmpabsgt(mant_b, mant_a)); /* The default multiplier is 1.0. If an underflow is detected (ie, * either the dividend is a denorm/zero, or the computed exponent is * less than or equal to a biased 0), force the multiplier to 0.0. */ mult = spu_and(one, (vector float)spu_cmpgt((vector signed int)exp, 0)); /* Force the multiplier to positive Smax (0x7FFFFFFF) and the biased exponent * to 127, if the divisor is denorm/zero or the computed biased exponent is * greater than 255. */ overflow = spu_or(spu_cmpeq(exp_b, 0), spu_cmpeq(spu_rlmask(exp, -30), 2)); exp = spu_sel(exp, (vector unsigned int)one, overflow); mult = spu_or(mult, (vector float)spu_rlmask(overflow, -1)); mult = spu_andc(mult, (vector float)spu_cmpeq(exp_a, 0)); /* Insert the exponent into the result and perform the * final multiplication. */ q2 = spu_sel(q2, (vector float)exp, exp_mask); q2 = spu_mul(q2, mult); return (q2); } #endif /* _DIVF4_H_ */ #endif /* __SPU__ */