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/*
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Crown Copyright (c) 1997
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This TenDRA(r) Computer Program is subject to Copyright
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owned by the United Kingdom Secretary of State for Defence
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acting through the Defence Evaluation and Research Agency
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(DERA). It is made available to Recipients with a
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royalty-free licence for its use, reproduction, transfer
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to other parties and amendment for any purpose not excluding
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product development provided that any such use et cetera
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shall be deemed to be acceptance of the following conditions:-
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(1) Its Recipients shall ensure that this Notice is
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reproduced upon any copies or amended versions of it;
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(2) Any amended version of it shall be clearly marked to
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show both the nature of and the organisation responsible
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for the relevant amendment or amendments;
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(3) Its onward transfer from a recipient to another
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party shall be deemed to be that party's acceptance of
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these conditions;
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(4) DERA gives no warranty or assurance as to its
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quality or suitability for any purpose and DERA accepts
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no liability whatsoever in relation to any use to which
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it may be put.
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*/
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/**********************************************************************
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$Author: release $
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$Date: 1998/01/17 15:56:05 $
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$Revision: 1.1.1.1 $
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$Log: is_worth.c,v $
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* Revision 1.1.1.1 1998/01/17 15:56:05 release
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* First version to be checked into rolling release.
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*
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* Revision 1.2 1995/09/12 10:59:28 currie
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* gcc pedanttry
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*
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* Revision 1.1 1995/04/13 09:08:06 currie
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* Initial revision
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*
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***********************************************************************/
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#include "config.h"
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#include "common_types.h"
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#include "tags.h"
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#include "expmacs.h"
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#include "exp.h"
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#include "shapemacs.h"
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#include "is_worth.h"
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#define true 1
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#define false 0
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int is_worth
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PROTO_N ( (c) )
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PROTO_T ( exp c )
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{ /* decide if constant c is worth declaring
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separately */
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unsigned char cnam = name (c);
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bool isflt = is_floating(name(sh(c)));
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if (name (sh (c)) == ptrhd && al1(sh(c))==1 )
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return 0; /* ptr bits */
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if (cnam == real_tag) return true;
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if (cnam == cont_tag && isflt && (name(son(c)) != name_tag || isglob(son(son(c))) )) {
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return true;
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}
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if (cnam == cont_tag && name (son (c)) == name_tag && isglob (son (son (c)))) {
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return true;
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}
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if (cnam == val_tag) { /* it is sometimes worthwhile extracting
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big constants from loops ... */
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long n = no (c);
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exp dad;
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if (n == 0 || bro(c)==nilexp) {
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return false;
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}
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dad = father (c);
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if (dad==nilexp) return false;
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switch (name (dad)) {
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case and_tag:
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{
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exp grandad = father (dad);
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if ( grandad != nilexp &&
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name (grandad) == test_tag && (n & (n - 1)) == 0 &&
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(props (grandad) == 5 || props (grandad) == 6) &&
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((name (bro (son (grandad))) == val_tag && no (bro (son (grandad))) == 0)
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|| (name (son (grandad)) == val_tag && no (son (grandad)) == 0))
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) { /* a & 2^n == 0 is transformed later to
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shift and test negative */
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return 0;
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}
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/* else next case */
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}
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case or_tag:
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case xor_tag:
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{
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return (n < 0 || n >= 0xffff);/* short literal operands */
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}
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case test_tag: return 1;
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case mult_tag: case offset_mult_tag:
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{
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if (n <= 0x7fff && n > -0x8000)
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return 0; /* short literal operands */
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/* a*2^n and a*2^(n+-1) are transformed later to shifts and adds
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*/
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return ((n & (n - 1)) != 0 && (n & (n + 1)) != 0 && ((n - 1) & (n - 2)) != 0);
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}
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case div1_tag:
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case div2_tag:
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case rem2_tag:
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{
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if (n <= 0x7fff && n > -0x8000)
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return 0 /* short literal operands */ ;
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/* a/2^n transformed later to shift */
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return ((n & (n - 1)) != 0);
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}
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default:
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{
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return (n > 0x7fff || n < -0x8000) /* short literal operands */ ;
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}
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} /* end sw */
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}
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return ((!is_o (cnam) && cnam != clear_tag) ||
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/* ignore simple things unless ... */
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(cnam == cont_tag && name (son (c)) == cont_tag &&
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name (son (son (c))) == name_tag)
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);
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}
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