Fix floating point math error detection

Working with floating point values were not handling errors correctly.

Most of the heavy lifting of performing floating point operations are
performed within C code.  Errors were not being properly caught which
resulted in invalid results.

Use the C99 provided functions for handling floating point exceptions.

int.asm

@@ -186,6 +186,8 @@ reg_fl:	db	0		; condition code register for numeric operations
 
 	align 8
 fl_flags:	d_word	0	; float flags
+	global	reg_flerr
+reg_flerr:  d_word 	0 	; Floatint point error
 
 	align	8
 ;  constants
@@ -798,17 +800,8 @@ setovr: mov	al,1		; set overflow indicator
 	pop	rsi
 	pop	rdi
 
-	mov	ax, word [reg_ra+6]	; get top 2 bytes
-	and	ax, 0x7ff0			; check for infinity or nan
-	add	ax, 0x10			; set/clear overflow accordingly
-	seto	byte [reg_fl]
-	jo	%%done
-
-	xor	rax, rax
-	fstsw	ax				; Get FPU status word
-	stmxcsr	[fl_flags]		; Get SSE status
-	or	rax, m_word [fl_flags]	; Combine
-	and	al, 0x1f			; INVALID | DENORM | DIVBYZERO | OVERFLOW | UNDERFLOW
+	mov 	rax, m_word [reg_flerr]	; Combine
+	and	al, 0x1f			; INVALID | DIVBYZERO | OVERFLOW | UNDERFLOW
 	mov	byte [reg_fl], al
 %%done: ret
 %endmacro
@@ -855,7 +848,11 @@ setovr: mov	al,1		; set overflow indicator
 	pop	rdx
 	pop	rsi
 	pop	rdi
-	ret
+	xor   rax,rax
+	mov	rax, [reg_flerr]		; 0x01       0x04        0x08       0x10
+	and	al, 0x1f			; INVALID | DIVBYZERO | OVERFLOW | UNDERFLOW
+	mov	byte [reg_fl], al
+%%done	ret
 %endmacro
 
 	math_op	atn_,f_atn

osint/float.c

@@ -27,6 +27,9 @@ This file is part of Macro SPITBOL.
 
 #include "port.h"
 #include <math.h>
+#include <fenv.h>
+#define FE_SBL_EXCEPT (FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW )
+
 #if (FLOAT & !FLTHDWR) | EXTFUN
 
 
@@ -45,28 +48,35 @@ void f_str() {			// store real
 }
 
 void f_adr() {			// add real
+	feclearexcept(FE_ALL_EXCEPT);
 	reg_ra += *reg_rp;
+	reg_flerr = fetestexcept(FE_SBL_EXCEPT);
 	return;
 }
 
 void f_sbr() {			// subtract real
+	feclearexcept(FE_ALL_EXCEPT);
 	reg_ra -= *reg_rp;
+	reg_flerr = fetestexcept(FE_SBL_EXCEPT);
 	return;
 }
 
 void f_mlr() {			// multiply real
+	feclearexcept(FE_ALL_EXCEPT);
 	reg_ra *= *reg_rp;
+	reg_flerr = fetestexcept(FE_SBL_EXCEPT);
 	return;
 }
 
 void f_dvr() {			// divide real
+	feclearexcept(FE_ALL_EXCEPT);
 	if (*reg_rp != 0.0) {
 		reg_ra /= *reg_rp;
-		reg_fl = 0;
+		reg_flerr = fetestexcept(FE_SBL_EXCEPT);
 	}
 	else {
-		reg_fl = 1;
 		reg_ra = NAN;
+		reg_flerr = FE_DIVBYZERO;
 	}
 	return;
 }

osint/math.c

@@ -13,44 +13,53 @@ Copyright 2012-2017 David Shields
  */
 
 #include "port.h"
-
 #include <errno.h>
 
 #if FLOAT & !MATHHDWR
 
 #include <math.h>
+#include <fenv.h>
 
 #ifndef errno
 int errno;
 #endif
 
+#define FE_SBL_EXCEPT (FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW )
+
 extern double inf;	// infinity
+extern word reg_flerr;	/* Floating point error */
 
 /*
  * f_atn - arctangent
  */
 void f_atn()
 {
-	reg_ra = atan(reg_ra);
+    feclearexcept(FE_ALL_EXCEPT);
+    reg_ra = atan(reg_ra);
+    reg_flerr = fetestexcept(FE_SBL_EXCEPT);
 }
 
 /*
  * f_chp - chop
  */
 void f_chp()
 {
+    feclearexcept(FE_ALL_EXCEPT);
     if (reg_ra >= 0.0)
         reg_ra =  floor(reg_ra);
     else
         reg_ra =  ceil(reg_ra);
+    reg_flerr = fetestexcept(FE_SBL_EXCEPT);
 }
 
 /*
  * f_cos - cosine
  */
 void f_cos()
 {
+    feclearexcept(FE_ALL_EXCEPT);
     reg_ra =  cos(reg_ra);
+    reg_flerr = fetestexcept(FE_SBL_EXCEPT);
 }
 
 
@@ -60,10 +69,12 @@ void f_cos()
 void f_etx()
 {
     errno = 0;
+    feclearexcept(FE_ALL_EXCEPT);
     reg_ra = exp(reg_ra);
     if (errno) {
-	reg_ra = inf;
+        reg_ra = inf;
     }
+    reg_flerr = fetestexcept(FE_SBL_EXCEPT);
 }
 
 /*
@@ -72,26 +83,33 @@ void f_etx()
 void f_lnf()
 {
     errno = 0;
+    feclearexcept(FE_ALL_EXCEPT);
+
     reg_ra = log(reg_ra);
     if (errno) {
-	reg_ra = inf;
+        reg_ra = inf;
     }
+    reg_flerr = fetestexcept(FE_SBL_EXCEPT);
 }
 
 /*
  * f_sin - sine
  */
 void f_sin()
 {
+    feclearexcept(FE_ALL_EXCEPT);
     reg_ra = sin(reg_ra);
+    reg_flerr = fetestexcept(FE_SBL_EXCEPT);
 }
 
 /*
  * f_sqr - square root  (reg_range checked by caller)
  */
 void f_sqr()
 {
+    feclearexcept(FE_ALL_EXCEPT);
     reg_ra = sqrt(reg_ra);
+    reg_flerr = fetestexcept(FE_SBL_EXCEPT);
 }
 
 /*
@@ -100,8 +118,10 @@ void f_sqr()
 void f_tan()
 {
     double result;
+    feclearexcept(FE_ALL_EXCEPT);
     result = tan(reg_ra);
     errno = 0;
     reg_ra = errno ? inf : result;
+    reg_flerr = fetestexcept(FE_SBL_EXCEPT);
 }
 #endif					// FLOAT & !MATHHDWR

osint/osint.h

@@ -17,6 +17,7 @@ Copyright 2012-2017 David Shields
 
 extern word	reg_cp, reg_wa, reg_wb, reg_wc, reg_xr, reg_xl, reg_xs, reg_w0;
 extern signed char	reg_fl;
+extern word 	reg_flerr;
 extern long	reg_ia;
 extern double 	reg_ra,*reg_rp;
 extern uword	minimal_id;