runtime: make complex division c99 compatible

- changes tests to check that the real and imaginary part of the go complex
  division result is equal to the result gcc produces for c99
- changes complex division code to satisfy new complex division test
- adds float functions isNan, isFinite, isInf, abs and copysign
  in the runtime package

Fixes #14644.

name                   old time/op  new time/op  delta
Complex128DivNormal-4  21.8ns ± 6%  13.9ns ± 6%  -36.37%  (p=0.000 n=20+20)
Complex128DivNisNaN-4  14.1ns ± 1%  15.0ns ± 1%   +5.86%  (p=0.000 n=20+19)
Complex128DivDisNaN-4  12.5ns ± 1%  16.7ns ± 1%  +33.79%  (p=0.000 n=19+20)
Complex128DivNisInf-4  10.1ns ± 1%  13.0ns ± 1%  +28.25%  (p=0.000 n=20+19)
Complex128DivDisInf-4  11.0ns ± 1%  20.9ns ± 1%  +90.69%  (p=0.000 n=16+19)
ComplexAlgMap-4        86.7ns ± 1%  86.8ns ± 2%     ~     (p=0.804 n=20+20)

Change-Id: I261f3b4a81f6cc858bc7ff48f6fd1b39c300abf0
Reviewed-on: https://go-review.googlesource.com/37441
Reviewed-by: Robert Griesemer <gri@golang.org>

1 files changed, 38 insertions, 34 deletions

diff --git a/test/cmplxdivide.c b/test/cmplxdivide.c
index a475cc24c9..89a2868b75 100644
--- a/test/cmplxdivide.c
+++ b/test/cmplxdivide.c
@@ -23,50 +23,63 @@
 #define nelem(x) (sizeof(x)/sizeof((x)[0]))
 
 double f[] = {
-	0,
-	1,
-	-1,
-	2,
+	0.0,
+	-0.0,
+	1.0,
+	-1.0,
+	2.0,
 	NAN,
 	INFINITY,
 	-INFINITY,
 };
 
-char*
-fmt(double g)
-{
+char* fmt(double g) {
 	static char buf[10][30];
 	static int n;
 	char *p;
-	
+
 	p = buf[n++];
-	if(n == 10)
+	if(n == 10) {
 		n = 0;
+	}
+
 	sprintf(p, "%g", g);
-	if(strcmp(p, "-0") == 0)
-		strcpy(p, "negzero");
-	return p;
-}
 
-int
-iscnan(double complex d)
-{
-	return !isinf(creal(d)) && !isinf(cimag(d)) && (isnan(creal(d)) || isnan(cimag(d)));
-}
+	if(strcmp(p, "0") == 0) {
+		strcpy(p, "zero");
+		return p;
+	}
+
+	if(strcmp(p, "-0") == 0) {
+		strcpy(p, "-zero");
+		return p;
+	}
 
-double complex zero;	// attempt to hide zero division from gcc
+	return p;
+}
 
-int
-main(void)
-{
+int main(void) {
 	int i, j, k, l;
 	double complex n, d, q;
-	
+
 	printf("// skip\n");
 	printf("// # generated by cmplxdivide.c\n");
 	printf("\n");
 	printf("package main\n");
-	printf("var tests = []Test{\n");
+	printf("\n");
+	printf("import \"math\"\n");
+	printf("\n");
+	printf("var (\n");
+	printf("\tnan     = math.NaN()\n");
+	printf("\tinf     = math.Inf(1)\n");
+	printf("\tzero    = 0.0\n");
+	printf(")\n");
+	printf("\n");
+	printf("var tests = []struct {\n");
+	printf("\tf, g complex128\n");
+	printf("\tout  complex128\n");
+	printf("}{\n");
+
 	for(i=0; i<nelem(f); i++)
 	for(j=0; j<nelem(f); j++)
 	for(k=0; k<nelem(f); k++)
@@ -74,17 +87,8 @@ main(void)
 		n = f[i] + f[j]*I;
 		d = f[k] + f[l]*I;
 		q = n/d;
-		
-		// BUG FIX.
-		// Gcc gets the wrong answer for NaN/0 unless both sides are NaN.
-		// That is, it treats (NaN+NaN*I)/0 = NaN+NaN*I (a complex NaN)
-		// but it then computes (1+NaN*I)/0 = Inf+NaN*I (a complex infinity).
-		// Since both numerators are complex NaNs, it seems that the
-		// results should agree in kind.  Override the gcc computation in this case.
-		if(iscnan(n) && d == 0)
-			q = (NAN+NAN*I) / zero;
 
-		printf("\tTest{complex(%s, %s), complex(%s, %s), complex(%s, %s)},\n",
+		printf("\t{complex(%s, %s), complex(%s, %s), complex(%s, %s)},\n",
 			fmt(creal(n)), fmt(cimag(n)),
 			fmt(creal(d)), fmt(cimag(d)),
 			fmt(creal(q)), fmt(cimag(q)));