Sometimes the compiler is very right! Found bug in bessel routines for float.

Original compiler error:

target arm C: libm <= bionic/libm/src/e_j0f.c
bionic/libm/src/e_j0f.c: In function 'j0f':
bionic/libm/src/e_j0f.c:66: warning: comparison between signed and unsigned integer expressions
bionic/libm/src/e_j0f.c: In function 'y0f':
bionic/libm/src/e_j0f.c:140: warning: comparison between signed and unsigned integer expressions
target arm C: libm <= bionic/libm/src/e_j1.c

It's subtle but ix is masked with 0x7f000000 so it can never ever have a value
greater than 0x80000000. So I switched to using the unmasked hx and added a
cast as a reward to the compiler for being right.

I checked the original routines that e_j0f.c was ported from (in e_j0.c) and
the double's don't use 0x80000000 so this issue didn't exist there.

Let that be a warning to those that just slap on casts to shut up the compiler,
sometimes it's sniffed out a bug for you. :-)

Similar fixes in the other functions.

Change-Id: I7a776e5d4721fc3a9e3bd89179b67e9af3a2ebfa

3 files changed, 7 insertions, 5 deletions

diff --git a/libm/src/e_j0f.c b/libm/src/e_j0f.c
index b872406..6b566bf 100644
--- a/libm/src/e_j0f.c
+++ b/libm/src/e_j0f.c
@@ -1,5 +1,6 @@
 /* e_j0f.c -- float version of e_j0.c.
  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ * Bugs in __ieee754_j0f and __ieee754_y0f fixed by Scott Turner 01/16/2010
  */
 
 /*
@@ -63,7 +64,7 @@ __ieee754_j0f(float x)
 	 * j0(x) = 1/sqrt(pi) * (P(0,x)*cc - Q(0,x)*ss) / sqrt(x)
 	 * y0(x) = 1/sqrt(pi) * (P(0,x)*ss + Q(0,x)*cc) / sqrt(x)
 	 */
-		if(ix>0x80000000) z = (invsqrtpi*cc)/sqrtf(x);
+		if(((uint32_t)hx)>0x80000000) z = (invsqrtpi*cc)/sqrtf(x);
 		else {
 		    u = pzerof(x); v = qzerof(x);
 		    z = invsqrtpi*(u*cc-v*ss)/sqrtf(x);
@@ -107,7 +108,7 @@ __ieee754_y0f(float x)
 	int32_t hx,ix;
 
 	GET_FLOAT_WORD(hx,x);
-        ix = 0x7fffffff&hx;
+        ix = hx&0x7fffffff;
     /* Y0(NaN) is NaN, y0(-inf) is Nan, y0(inf) is 0  */
 	if(ix>=0x7f800000) return  one/(x+x*x);
         if(ix==0) return -one/zero;
@@ -137,7 +138,7 @@ __ieee754_y0f(float x)
                     if ((s*c)<zero) cc = z/ss;
                     else            ss = z/cc;
                 }
-                if(ix>0x80000000) z = (invsqrtpi*ss)/sqrtf(x);
+                if(((uint32_t)hx)>0x80000000) z = (invsqrtpi*ss)/sqrtf(x);
                 else {
                     u = pzerof(x); v = qzerof(x);
                     z = invsqrtpi*(u*ss+v*cc)/sqrtf(x);
diff --git a/libm/src/e_j1f.c b/libm/src/e_j1f.c
index 539399e..ea05774 100644
--- a/libm/src/e_j1f.c
+++ b/libm/src/e_j1f.c
@@ -1,5 +1,6 @@
 /* e_j1f.c -- float version of e_j1.c.
  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ * Bug in __ieee754_j1f fixed by Scott Turner 1/16/2010
  */
 
 /*
@@ -64,7 +65,7 @@ __ieee754_j1f(float x)
 	 * j1(x) = 1/sqrt(pi) * (P(1,x)*cc - Q(1,x)*ss) / sqrt(x)
 	 * y1(x) = 1/sqrt(pi) * (P(1,x)*ss + Q(1,x)*cc) / sqrt(x)
 	 */
-		if(ix>0x80000000) z = (invsqrtpi*cc)/sqrtf(y);
+		if(((uint32_t)hx)>0x80000000) z = (invsqrtpi*cc)/sqrtf(y);
 		else {
 		    u = ponef(y); v = qonef(y);
 		    z = invsqrtpi*(u*cc-v*ss)/sqrtf(y);
diff --git a/libm/src/e_jnf.c b/libm/src/e_jnf.c
index 029dba6..a61fb68 100644
--- a/libm/src/e_jnf.c
+++ b/libm/src/e_jnf.c
@@ -186,7 +186,7 @@ __ieee754_ynf(int n, float x)
 	b = __ieee754_y1f(x);
 	/* quit if b is -inf */
 	GET_FLOAT_WORD(ib,b);
-	for(i=1;i<n&&ib!=0xff800000;i++){
+	for(i=1; i<n && (((uint32_t)ib) != 0xff800000); i++){
 	    temp = b;
 	    b = ((float)(i+i)/x)*b - a;
 	    GET_FLOAT_WORD(ib,b);