From 8e684b1ddc43234032f17b1be537cedd83c427dd Mon Sep 17 00:00:00 2001
From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Wed, 7 May 2025 13:37:15 +0000
Subject: [PATCH] math: Fix UB in ldbl-128ibm ilogb

UBSAN: Undefined behaviour in ../sysdeps/ieee754/ldbl-128ibm/e_ilogbl.c:45:37 left shift of 4611686018427387904 by 1 cannot be represented in type 'long int'
---
 sysdeps/ieee754/ldbl-128ibm/e_ilogbl.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sysdeps/ieee754/ldbl-128ibm/e_ilogbl.c b/sysdeps/ieee754/ldbl-128ibm/e_ilogbl.c
index 9daa970f84..b86c841d08 100644
--- a/sysdeps/ieee754/ldbl-128ibm/e_ilogbl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_ilogbl.c
@@ -27,6 +27,7 @@ static char rcsid[] = "$NetBSD: $";
 #include <math.h>
 #include <math_private.h>
 #include <math_ldbl_opt.h>
+#include <stdbit.h>
 
 int __ieee754_ilogbl(long double x)
 {
@@ -42,7 +43,8 @@ int __ieee754_ilogbl(long double x)
 	    if(hx==0)
 		return FP_ILOGB0;	/* ilogbl(0) = FP_ILOGB0 */
 	    else			/* subnormal x */
-		for (ix = -1022, hx<<=11; hx>0; hx<<=1) ix -=1;
+		//for (ix = -1022, hx<<=11; hx>0; hx<<=1) ix -=1;
+		ix = -1022 - stdc_leading_zeros (hx << 11);
 	    return ix;
 	}
 	else if (hx < 0x7ff0000000000000LL)
-- 
2.47.2