raze/libraries/gdtoa/arithchk.c

/****************************************************************
Copyright (C) 1997, 1998 Lucent Technologies
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
THIS SOFTWARE.
****************************************************************/

/* Try to deduce arith.h from arithmetic properties. */

#include <stdio.h>

 static int dalign;
 typedef struct
Akind {
	char *name;
	int   kind;
	} Akind;

 static Akind
IEEE_8087	= { "IEEE_8087", 1 },
IEEE_MC68k	= { "IEEE_MC68k", 2 },
IBM		= { "IBM", 3 },
VAX		= { "VAX", 4 },
CRAY		= { "CRAY", 5};

 static Akind *
Lcheck()
{
	union {
		double d;
		long L[2];
		} u;
	struct {
		double d;
		long L;
		} x[2];

	if (sizeof(x) > 2*(sizeof(double) + sizeof(long)))
		dalign = 1;
	u.L[0] = u.L[1] = 0;
	u.d = 1e13;
	if (u.L[0] == 1117925532 && u.L[1] == -448790528)
		return &IEEE_MC68k;
	if (u.L[1] == 1117925532 && u.L[0] == -448790528)
		return &IEEE_8087;
	if (u.L[0] == -2065213935 && u.L[1] == 10752)
		return &VAX;
	if (u.L[0] == 1267827943 && u.L[1] == 704643072)
		return &IBM;
	return 0;
	}

 static Akind *
icheck()
{
	union {
		double d;
		int L[2];
		} u;
	struct {
		double d;
		int L;
		} x[2];

	if (sizeof(x) > 2*(sizeof(double) + sizeof(int)))
		dalign = 1;
	u.L[0] = u.L[1] = 0;
	u.d = 1e13;
	if (u.L[0] == 1117925532 && u.L[1] == -448790528)
		return &IEEE_MC68k;
	if (u.L[1] == 1117925532 && u.L[0] == -448790528)
		return &IEEE_8087;
	if (u.L[0] == -2065213935 && u.L[1] == 10752)
		return &VAX;
	if (u.L[0] == 1267827943 && u.L[1] == 704643072)
		return &IBM;
	return 0;
	}

char *emptyfmt = "";	/* avoid possible warning message with printf("") */

 static Akind *
ccheck()
{
	union {
		double d;
		long L;
		} u;
	long Cray1;

	/* Cray1 = 4617762693716115456 -- without overflow on non-Crays */
	Cray1 = printf("%s", emptyfmt) < 0 ? 0 : 4617762;
	if (printf(emptyfmt, Cray1) >= 0)
		Cray1 = 1000000*Cray1 + 693716;
	if (printf(emptyfmt, Cray1) >= 0)
		Cray1 = 1000000*Cray1 + 115456;
	u.d = 1e13;
	if (u.L == Cray1)
		return &CRAY;
	return 0;
	}

 static int
fzcheck()
{
	double a, b;
	int i;

	a = 1.;
	b = .1;
	for(i = 155;; b *= b, i >>= 1) {
		if (i & 1) {
			a *= b;
			if (i == 1)
				break;
			}
		}
	b = a * a;
	return b == 0.;
	}

 int
main()
{
	Akind *a = 0;
	int Ldef = 0;
	FILE *f;

#ifdef WRITE_ARITH_H	/* for Symantec's buggy "make" */
	f = fopen("arith.h", "w");
	if (!f) {
		printf("Cannot open arith.h\n");
		return 1;
		}
#else
	f = stdout;
#endif

	if (sizeof(double) == 2*sizeof(long))
		a = Lcheck();
	else if (sizeof(double) == 2*sizeof(int)) {
		Ldef = 1;
		a = icheck();
		}
	else if (sizeof(double) == sizeof(long))
		a = ccheck();
	if (a) {
		fprintf(f, "#define %s\n#define Arith_Kind_ASL %d\n",
			a->name, a->kind);
		if (Ldef)
			fprintf(f, "#define Long int\n#define Intcast (int)(long)\n");
		if (dalign)
			fprintf(f, "#define Double_Align\n");
		if (sizeof(char*) == 8)
			fprintf(f, "#define X64_bit_pointers\n");
#ifndef NO_LONG_LONG
		if (sizeof(long long) < 8)
#endif
			fprintf(f, "#define NO_LONG_LONG\n");
		if (a->kind <= 2 && fzcheck())
			fprintf(f, "#define Sudden_Underflow\n");
		return 0;
		}
	fprintf(f, "/* Unknown arithmetic */\n");
	return 1;
	}