/*
	This C language subroutine computes the greatest
	integer less then or equal to the input.

	The Run Time Library for the C Language.

	Gordon A. Sterling	(617) 461 - 3076
	DSP Development Tools Engineering

	Created on 4/28/90
	Updated on 5/94 by AS

	#include <math.h>			    <Header>
	double floor(double x);			    <Prototype>
*/

#include "lib_glob.h"
#include "mth_glob.h"

.SEGMENT/CODE	Code_Space_Name;
.FILE 		RTL_FILENAME;

.GLOBAL	    	_floor;

_floor:	    put(R6);
	    put(R7);

	    reads(R4,1);
	    reads(R8,2);

	    R0=PASS R4, R12=R8;

	    R4=FEXT R0 BY 20:11;	/*Extract biased exponent*/
	    R3=D_EXP_BIAS;
	    R4=R4-R3, R1=R12;		/*Compute unbiased exponent*/
	    R3=52;
	    COMP(R4,R3);		/*Test for zero fraction*/
	    IF GT JUMP (PC, restore_state); /*Return already set to zero*/
	    R8=0xFFFFFFFF;
	    R2=52;
	    R2=R2-R4;
	    R7=ASHIFT R8 BY R2;		/*Determine mask*/
	    R7=R12 AND R7;		/*R7 holds LSW integer part only*/
	    R2=20;
	    R2=R2-R4, R1=R7;
	    R8=ASHIFT R8 BY R2;
	    R6=R0 AND R8;		/*R6 holds MSW integer part only*/
	    F2=PASS F0, R0=R6;	/* If the original input is pos.*/
	    IF GE JUMP (PC, restore_state); /* just remove the fraction	*/

					/* Otherwise, for a neg value we*/
	    put(R12);			/* need to subtract integer val	*/
	    put(R2);			/* from the original value to	*/
    	    put(R1);			/* determine if there is a 	*/
	    put(R0);			/* fractional part remaining.	*/

	    CALLER_HOLD(R2)
	    CALLER_SWAP
	    RTLCALL (PC, ___dsub) (DB);
	    SAVE_OLD_FRAME(R2)
label_1:    SAVE_RET_ADDR
		
	alter(4);			/* Clean parameters from stack	*/
	R4=R0 OR R1;			/* Test for zero fraction, if it*/
	IF EQ JUMP (PC, restore_state) (DB);	/* is, return with result, else	*/
	R0=PASS R6, R1=R7;		/* subtract one from result	*/
	R8=D_ONE_LSW;			

	R4=D_ONE_MSW;
	put(R8);
	put(R4);
        put(R1);			/*Store LSW of integer*/
	put(R0);

	CALLER_HOLD(R2)
	CALLER_SWAP
	RTLCALL (PC, ___dsub) (DB);
	SAVE_OLD_FRAME(R2)
label_2:SAVE_RET_ADDR
	
	alter(4);
	    
restore_state:	FETCH_RETURN
		get(R7,2);
		get(R6,3);
		RETURN (DB);
		RESTORE_STACK
		RESTORE_FRAME

.ENDSEG;