[glibc/azanella/ubsan-undef] math: Fix UB in float128 atan2

[Adhemerval Zanella]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=8a45f66e63439cf94d7d5e300600f83fc15a3325

commit 8a45f66e63439cf94d7d5e300600f83fc15a3325
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Tue Apr 22 15:59:02 2025 -0300

    math: Fix UB in float128 atan2
    
    UBSAN: Undefined behaviour in ../sysdeps/ieee754/float128/../ldbl-128/e_atan2l.c:68:9 unsigned integer overflow: 9223372036854775808 - 4611404543450677248 cannot be represened in type 'long int'

Diff:
---
 sysdeps/ieee754/ldbl-128/e_atan2l.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sysdeps/ieee754/ldbl-128/e_atan2l.c b/sysdeps/ieee754/ldbl-128/e_atan2l.c
index cdf08170f6..d2701084de 100644
--- a/sysdeps/ieee754/ldbl-128/e_atan2l.c
+++ b/sysdeps/ieee754/ldbl-128/e_atan2l.c
@@ -65,7 +65,7 @@ __ieee754_atan2l(_Float128 y, _Float128 x)
 	if(((ix|((lx|-lx)>>63))>0x7fff000000000000LL)||
 	   ((iy|((ly|-ly)>>63))>0x7fff000000000000LL))	/* x or y is NaN */
 	   return x+y;
-	if(((hx-0x3fff000000000000LL)|lx)==0) return __atanl(y);   /* x=1.0L */
+	if((((uint64_t)hx-0x3fff000000000000LL)|lx)==0) return __atanl(y);   /* x=1.0L */
 	m = ((hy>>63)&1)|((hx>>62)&2);	/* 2*sign(x)+sign(y) */
 
     /* when y = 0 */