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Paul Mackerras c350bc1f25 FPU: Implement fsqrt[s] and add a test for fsqrt ... This implements the floating square-root calculation using a table lookup of the inverse square root approximation, followed by three iterations of Goldschmidt's algorithm, which gives estimates of both sqrt(FRB) and 1/sqrt(FRB). Then the residual is calculated as FRB - R * R and that is multiplied by the 1/sqrt(FRB) estimate to get an adjustment to R. The residual and the adjustment can be negative, and since we have an unsigned multiplier, the upper bits can be wrong. In practice the adjustment fits into an 8-bit signed value, and the bottom 8 bits of the adjustment product are correct, so we sign-extend them, divide by 4 (because R is in 10.54 format) and add them to R. Finally the residual is calculated again and compared to 2*R+1 to see if a final increment is needed. Then the result is rounded and written back. This implements fsqrts as fsqrt, but with rounding to single precision and underflow/overflow calculation using the single-precision exponent range. This could be optimized later. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>		4 years ago
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Makefile	tests: Add a test for FP loads and stores	4 years ago
fpu.c	FPU: Implement fsqrt[s] and add a test for fsqrt	4 years ago
head.S	tests/fpu: Add tests for basic FPSCR function and interrupt generation	4 years ago
powerpc.lds	tests: Add a test for FP loads and stores	4 years ago