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25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Use is subject to license terms.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fmax(x,y) returns the larger of x and y. If just one of the
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * arguments is NaN, fmax returns the other argument. If both
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * arguments are NaN, fmax returns NaN (ideally, one of the
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * argument NaNs).
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * C99 does not require that fmax(-0,+0) = fmax(+0,-0) = +0, but
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ideally fmax should satisfy this.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * C99 makes no mention of exceptions for fmax. I suppose ideally
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * either fmax never raises any exceptions or else it raises the
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * invalid operation exception if and only if some argument is a
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * signaling NaN. In the former case, fmax should always return
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * one of its arguments. In the latter, fmax shouldn't return a
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * signaling NaN, although when both arguments are signaling NaNs,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * this ideal is at odds with the stipulation that fmax should
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * always return one of its arguments.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Commutativity of fmax follows from the properties listed above
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * except when both arguments are NaN. In that case, fmax may be
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * declared commutative by fiat because there is no portable way
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * to tell different NaNs apart. Ideally fmax would be truly com-
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * mutative for all arguments.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * On SPARC V8, fmax must involve tests and branches. Ideally,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * an implementation on SPARC V9 should avoid branching, using
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * conditional moves instead where necessary, and be as efficient
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * as possible in its use of other resources.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * It appears to be impossible to attain all of the aforementioned
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ideals simultaneously. The implementation below satisfies the
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * following (on SPARC):
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 1. fmax(x,y) returns the larger of x and y if neither x nor y
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * is NaN and the non-NaN argument if just one of x or y is NaN.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * If both x and y are NaN, fmax(x,y) returns x unchanged.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 2. fmax(-0,+0) = fmax(+0,-0) = +0.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 3. If either argument is a signaling NaN, fmax raises the invalid
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * operation exception. Otherwise, it raises no exceptions.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis#include "libm.h" /* for isgreaterequal macro */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * On SPARC v8plus/v9, this could be implemented as follows
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * (assuming %f0 = x, %f1 = y, return value left in %f0):
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fcmps %fcc0,%f1,%f1
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fmovsu %fcc0,%f0,%f1
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fcmps %fcc0,%f0,%f1
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fmovsul %fcc0,%f1,%f0
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * and %l0,%l1,%l2
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * sethi %hi(0x80000000),%l3
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * andn %l3,%l2,%l2
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * andn %l0,%l2,%l0
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * If VIS instructions are available, use this code instead:
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fcmps %fcc0,%f1,%f1
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fmovsu %fcc0,%f0,%f1
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fcmps %fcc0,%f0,%f1
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fmovsul %fcc0,%f1,%f0
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fands %f0,%f1,%f2
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fnegs %f3,%f3
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fandnot2s %f3,%f2,%f2
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fandnot2s %f0,%f2,%f0
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * If VIS 3.0 instructions are available, use this:
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * flcmps %fcc0,%f0,%f1
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * fmovslg %fcc0,%f1,%f0 ! move if %fcc0 is 1 or 2
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* if y is nan, replace it by x */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* if x is nan, replace it by y */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* At this point, x and y are either both numeric, or both NaN */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * clear the sign of the result if either x or y has its sign clear