xref: /aosp_15_r20/external/musl/src/math/floor.c (revision c9945492fdd68bbe62686c5b452b4dc1be3f8453)
1*c9945492SAndroid Build Coastguard Worker #include "libm.h"
2*c9945492SAndroid Build Coastguard Worker 
3*c9945492SAndroid Build Coastguard Worker #if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
4*c9945492SAndroid Build Coastguard Worker #define EPS DBL_EPSILON
5*c9945492SAndroid Build Coastguard Worker #elif FLT_EVAL_METHOD==2
6*c9945492SAndroid Build Coastguard Worker #define EPS LDBL_EPSILON
7*c9945492SAndroid Build Coastguard Worker #endif
8*c9945492SAndroid Build Coastguard Worker static const double_t toint = 1/EPS;
9*c9945492SAndroid Build Coastguard Worker 
floor(double x)10*c9945492SAndroid Build Coastguard Worker double floor(double x)
11*c9945492SAndroid Build Coastguard Worker {
12*c9945492SAndroid Build Coastguard Worker 	union {double f; uint64_t i;} u = {x};
13*c9945492SAndroid Build Coastguard Worker 	int e = u.i >> 52 & 0x7ff;
14*c9945492SAndroid Build Coastguard Worker 	double_t y;
15*c9945492SAndroid Build Coastguard Worker 
16*c9945492SAndroid Build Coastguard Worker 	if (e >= 0x3ff+52 || x == 0)
17*c9945492SAndroid Build Coastguard Worker 		return x;
18*c9945492SAndroid Build Coastguard Worker 	/* y = int(x) - x, where int(x) is an integer neighbor of x */
19*c9945492SAndroid Build Coastguard Worker 	if (u.i >> 63)
20*c9945492SAndroid Build Coastguard Worker 		y = x - toint + toint - x;
21*c9945492SAndroid Build Coastguard Worker 	else
22*c9945492SAndroid Build Coastguard Worker 		y = x + toint - toint - x;
23*c9945492SAndroid Build Coastguard Worker 	/* special case because of non-nearest rounding modes */
24*c9945492SAndroid Build Coastguard Worker 	if (e <= 0x3ff-1) {
25*c9945492SAndroid Build Coastguard Worker 		FORCE_EVAL(y);
26*c9945492SAndroid Build Coastguard Worker 		return u.i >> 63 ? -1 : 0;
27*c9945492SAndroid Build Coastguard Worker 	}
28*c9945492SAndroid Build Coastguard Worker 	if (y > 0)
29*c9945492SAndroid Build Coastguard Worker 		return x + y - 1;
30*c9945492SAndroid Build Coastguard Worker 	return x + y;
31*c9945492SAndroid Build Coastguard Worker }
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