On 8/29/19 9:20 AM, Elen Kalda wrote: > Hi all, > > Advice and help needed! > > This patch makes changes to the the complex division in GCC. The algorithm > used is same as in https://gcc.gnu.org/ml/gcc-patches/2019-08/msg01629.html - > same problems, same improvement in robustness, same loss in accuracy. > > Since Baudin adds another underflow check, two more basic blocks get added > during the cplxlower1 pass. > > No problems with bootstrap on aarch64-none-linux-gnu. Unsurprisingly, there > are regressions in gcc/testsuite/gcc.dg/torture/builtin-math-7.c. As in the > patch linked above, the regressions in that test are due to the loss in > accuracy. > > To evaluate the performance, the same test which generates 360 000 000 random > numbers was used. Doing one less division results in a nice 11.32% > improvement in performance: > > | CPU time > -------------------- > smiths | 7 290 996 > b1div | 6 465 590 > > That implementation works (in a sense that it produces an expected result), > but it could be made more efficient and clean. As an example, the cplxlower1 > pass assigns one variable to another variable, which seems redundant: > > [...] > > <bb 3> [local count: 1063004407]: > # i_19 = PHI <0(2), i_15(7)> > _9 = REALPART_EXPR <x[i_19]>; > _7 = IMAGPART_EXPR <x[i_19]>; > _1 = COMPLEX_EXPR <_9, _7>; > _18 = REALPART_EXPR <y[i_19]>; > _17 = IMAGPART_EXPR <y[i_19]>; > _2 = COMPLEX_EXPR <_18, _17>; > _16 = ABS_EXPR <_18>; > _21 = ABS_EXPR <_17>; > _22 = _16 > _21; > if (_22 != 0) > goto <bb 9>; [50.00%] > else > goto <bb 10>; [50.00%] > > <bb 9> [local count: 531502204]: > _23 = _17 / _18; > _24 = _17 * _23; > _25 = _18 + _24; > _26 = 1.0e+0 / _25; > _27 = _23 == 0.0; > if (_27 != 0) > goto <bb 12>; [50.00%] > else > goto <bb 13>; [50.00%] > > <bb 12> [local count: 265751102]: > _28 = _7 / _18; > _29 = _17 * _28; > _30 = _9 + _29; > _31 = _26 * _30; > _32 = _9 / _18; > _33 = _17 * _32; > _34 = _7 - _33; > _35 = _26 * _34; > _83 = _31; <----------------------- could these extra assignments be > avoided? > _84 = _35; <-----------------------| > goto <bb 11>; [100.00%] I wouldn't really worry about them at this point. They'll almost certainly get propagated away as they're simple copies.
> > 2019-08-29 Elen Kalda <elen.ka...@arm.com> > > * fold-const.c (fold_negate_const): Make the fold_negate_const function > non-static > (const_binop): Implement Baudin's algorithm for complex division > * fold-const.h (fold_negate_const): Add a fold_negate_const function > declaration > * tree-complex.c (complex_div_internal_wide): New function to aid with > the > wide complex division > (expand_complex_div_wide): Implement Baudin's algorithm for complex > division I'd like Joseph to chime in when he can. jeff
