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Quick fix for stack buffer overrun in rev.1.13. Oops. The prec == 1
arg to __kernel_rem_pio2() gives 53-bit (double) precision, not single precision and/or the array dimension like I thought. prec == 2 is used in e_rem_pio2.c for double precision although it is documented to be for 64-bit (extended) precision, and I just reduced it by 1 thinking that this would give the value suitable for 24-bit (float) precision. Reducing it 1 more to the documented value for float precision doesn't actually work (it gives errors of ~0.75 ulps in the reduced arg, but errors of much less than 0.5 ulps are needed; the bug seems to be in kernel_rem_pio2.c). Keep using a value 1 larger than the documented value but supply an array large enough hold the extra unused result from this. The bug can also be fixed quickly by increasing init_jk[0] in k_rem_pio2.c from 2 to 3. This gives behaviour identical to using prec == 1 except it doesn't create the extra result. It isn't clear how the precision bug affects higher precisions. 113-bit (quad) is the largest precision, so there is no way to use a large precision to fix it.
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=152706
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@ -62,7 +62,7 @@ pio2_1t = 6.07710050650619224932e-11; /* 0x3DD0B461, 0x1A626331 */
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int32_t __ieee754_rem_pio2f(float x, float *y)
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{
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double z,w,t,r,fn;
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double tx[3];
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double tx[3],ty[2];
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int32_t e0,i,nx,n,ix,hx;
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GET_FLOAT_WORD(hx,x);
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@ -98,9 +98,9 @@ pio2_1t = 6.07710050650619224932e-11; /* 0x3DD0B461, 0x1A626331 */
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tx[2] = z;
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nx = 3;
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while(tx[nx-1]==zero) nx--; /* skip zero term */
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n = __kernel_rem_pio2(tx,&z,e0,nx,1,two_over_pi);
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y[0] = z;
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y[1] = z - y[0];
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n = __kernel_rem_pio2(tx,ty,e0,nx,1,two_over_pi);
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y[0] = ty[0];
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y[1] = ty[0] - y[0];
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if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;}
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return n;
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}
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