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

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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
This commit is contained in:
Scott Turner 2010-01-16 11:30:44 -05:00 committed by Jean-Baptiste Queru
parent 0be7eda75a
commit c1f8dd9f0b
3 changed files with 7 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
libm/src/e_j0f.c
View File

@ -1,5 +1,6 @@
/* e_j0f.c -- float version of e_j0.c. /* e_j0f.c -- float version of e_j0.c.
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. * 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) * 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) * 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 { else {
u = pzerof(x); v = qzerof(x); u = pzerof(x); v = qzerof(x);
z = invsqrtpi*(u*cc-v*ss)/sqrtf(x); z = invsqrtpi*(u*cc-v*ss)/sqrtf(x);
@ -107,7 +108,7 @@ __ieee754_y0f(float x)
int32_t hx,ix; int32_t hx,ix;
GET_FLOAT_WORD(hx,x); GET_FLOAT_WORD(hx,x);
ix = 0x7fffffff&hx; ix = hx&0x7fffffff;
/* Y0(NaN) is NaN, y0(-inf) is Nan, y0(inf) is 0 */ /* Y0(NaN) is NaN, y0(-inf) is Nan, y0(inf) is 0 */
if(ix>=0x7f800000) return one/(x+x*x); if(ix>=0x7f800000) return one/(x+x*x);
if(ix==0) return -one/zero; if(ix==0) return -one/zero;
@ -137,7 +138,7 @@ __ieee754_y0f(float x)
if ((s*c)<zero) cc = z/ss; if ((s*c)<zero) cc = z/ss;
else ss = z/cc; else ss = z/cc;
} }
if(ix>0x80000000) z = (invsqrtpi*ss)/sqrtf(x); if(((uint32_t)hx)>0x80000000) z = (invsqrtpi*ss)/sqrtf(x);
else { else {
u = pzerof(x); v = qzerof(x); u = pzerof(x); v = qzerof(x);
z = invsqrtpi*(u*ss+v*cc)/sqrtf(x); z = invsqrtpi*(u*ss+v*cc)/sqrtf(x);

3
libm/src/e_j1f.c
View File

@ -1,5 +1,6 @@
/* e_j1f.c -- float version of e_j1.c. /* e_j1f.c -- float version of e_j1.c.
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. * 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) * 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) * 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 { else {
u = ponef(y); v = qonef(y); u = ponef(y); v = qonef(y);
z = invsqrtpi*(u*cc-v*ss)/sqrtf(y); z = invsqrtpi*(u*cc-v*ss)/sqrtf(y);

2
libm/src/e_jnf.c
View File

@ -186,7 +186,7 @@ __ieee754_ynf(int n, float x)
b = __ieee754_y1f(x); b = __ieee754_y1f(x);
/* quit if b is -inf */ /* quit if b is -inf */
GET_FLOAT_WORD(ib,b); 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; temp = b;
b = ((float)(i+i)/x)*b - a; b = ((float)(i+i)/x)*b - a;
GET_FLOAT_WORD(ib,b); GET_FLOAT_WORD(ib,b);