A few minor corrections, including some from bde:

- When y/x is huge, it's faster and more accurate to return pi/2
  instead of pi - pi/2.
- There's no need for 3 lines of bit fiddling to compute -z.
- Fix a comment.

3 files changed, 16 insertions, 17 deletions

diff --git a/lib/msun/src/e_atan2.c b/lib/msun/src/e_atan2.c
index 399822a..a4a985b 100644
--- a/lib/msun/src/e_atan2.c
+++ b/lib/msun/src/e_atan2.c
@@ -109,17 +109,15 @@ __ieee754_atan2(double y, double x)
 
     /* compute y/x */
 	k = (iy-ix)>>20;
-	if(k > 60) z=pi_o_2+0.5*pi_lo; 	/* |y/x| >  2**60 */
-	else if(hx<0&&k<-60) z=0.0; 	/* |y|/x < -2**60 */
+	if(k > 60) {		 	/* |y/x| >  2**60 */
+	    z=pi_o_2+0.5*pi_lo;
+	    m&=1;
+	}
+	else if(hx<0&&k<-60) z=0.0; 	/* 0 > |y|/x > -2**-60 */
 	else z=atan(fabs(y/x));		/* safe to do y/x */
 	switch (m) {
 	    case 0: return       z  ;	/* atan(+,+) */
-	    case 1: {
-	    	      u_int32_t zh;
-		      GET_HIGH_WORD(zh,z);
-		      SET_HIGH_WORD(z,zh ^ 0x80000000);
-		    }
-		    return       z  ;	/* atan(-,+) */
+	    case 1: return      -z  ;	/* atan(-,+) */
 	    case 2: return  pi-(z-pi_lo);/* atan(+,-) */
 	    default: /* case 3 */
 	    	    return  (z-pi_lo)-pi;/* atan(-,-) */
diff --git a/lib/msun/src/e_atan2f.c b/lib/msun/src/e_atan2f.c
index a48ada1..3b6818a 100644
--- a/lib/msun/src/e_atan2f.c
+++ b/lib/msun/src/e_atan2f.c
@@ -80,17 +80,15 @@ __ieee754_atan2f(float y, float x)
 
     /* compute y/x */
 	k = (iy-ix)>>23;
-	if(k > 26) z=pi_o_2+(float)0.5*pi_lo; 	/* |y/x| >  2**26 */
-	else if(hx<0&&k<-26) z=0.0; 	/* |y|/x < -2**26 */
+	if(k > 26) {			/* |y/x| >  2**26 */
+	    z=pi_o_2+(float)0.5*pi_lo;
+	    m&=1;
+	}
+	else if(hx<0&&k<-26) z=0.0; 	/* 0 > |y|/x > -2**-26 */
 	else z=atanf(fabsf(y/x));	/* safe to do y/x */
 	switch (m) {
 	    case 0: return       z  ;	/* atan(+,+) */
-	    case 1: {
-	    	      u_int32_t zh;
-		      GET_FLOAT_WORD(zh,z);
-		      SET_FLOAT_WORD(z,zh ^ 0x80000000);
-		    }
-		    return       z  ;	/* atan(-,+) */
+	    case 1: return      -z  ;	/* atan(-,+) */
 	    case 2: return  pi-(z-pi_lo);/* atan(+,-) */
 	    default: /* case 3 */
 	    	    return  (z-pi_lo)-pi;/* atan(-,-) */
diff --git a/lib/msun/src/e_atan2l.c b/lib/msun/src/e_atan2l.c
index 0071a7c..0326482 100644
--- a/lib/msun/src/e_atan2l.c
+++ b/lib/msun/src/e_atan2l.c
@@ -104,7 +104,10 @@ atan2l(long double y, long double x)
 
     /* compute y/x */
 	k = expty-exptx;
-	if(k > LDBL_MANT_DIG+2) z=pio2_hi+pio2_lo;	/* |y/x| huge */
+	if(k > LDBL_MANT_DIG+2) {			/* |y/x| huge */
+	    z=pio2_hi+pio2_lo;
+	    m&=1;
+	}
 	else if(expsignx<0&&k<-LDBL_MANT_DIG-2) z=0.0; 	/* |y/x| tiny, x<0 */
 	else z=atanl(fabsl(y/x));		/* safe to do y/x */
 	switch (m) {