[glibc] math: Fix x86_64 tanh _FloatN aliases binding to the FMA variant [BZ 34465]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b01abba04a954cbd6b2834c0643a08685a915fe5

commit b01abba04a954cbd6b2834c0643a08685a915fe5
Author: Adhemerval Zanella <[email protected]>
Date:   Thu Jul 30 08:55:54 2026 -0300

    math: Fix x86_64 tanh _FloatN aliases binding to the FMA variant [BZ 34465]
    
    The generic implementation emits libm_alias_double unconditionally, so
    tanhf32x and tanhf64 bind directly to __tanh_fma.
    
    Guard the alias with '#ifndef __tanh' and emit it from the dispatcher,
    as sin.  Also remove the stale __expm1 defines, unused since tanh moved
    to CORE-MATH.
    
    Checked on x86_64-linux-gnu, and with 'qemu-x86_64 -cpu Nehalem'.
    
    Reported-by: Michael Brunnbauer <[email protected]>

Diff:
---
 sysdeps/ieee754/dbl-64/s_tanh.c           | 2 ++
 sysdeps/x86_64/fpu/multiarch/s_tanh-fma.c | 6 ------
 sysdeps/x86_64/fpu/multiarch/s_tanh.c     | 5 ++---
 3 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/sysdeps/ieee754/dbl-64/s_tanh.c b/sysdeps/ieee754/dbl-64/s_tanh.c
index 2029de8fa5..ef80b9edb6 100644
--- a/sysdeps/ieee754/dbl-64/s_tanh.c
+++ b/sysdeps/ieee754/dbl-64/s_tanh.c
@@ -283,4 +283,6 @@ __tanh (double x)
     return as_tanh_database (x, res);
   return res;
 }
+#ifndef __tanh
 libm_alias_double (__tanh, tanh)
+#endif
diff --git a/sysdeps/x86_64/fpu/multiarch/s_tanh-fma.c b/sysdeps/x86_64/fpu/multiarch/s_tanh-fma.c
index 1b808b1227..1e6b33740a 100644
--- a/sysdeps/x86_64/fpu/multiarch/s_tanh-fma.c
+++ b/sysdeps/x86_64/fpu/multiarch/s_tanh-fma.c
@@ -1,10 +1,4 @@
 #define __tanh __tanh_fma
-#define __expm1 __expm1_fma
-
-/* NB: __expm1 may be expanded to __expm1_fma in the following
-   prototypes.  */
-extern long double __expm1l (long double);
-extern long double __expm1f128 (long double);
 
 #define SECTION __attribute__ ((section (".text.fma")))
 
diff --git a/sysdeps/x86_64/fpu/multiarch/s_tanh.c b/sysdeps/x86_64/fpu/multiarch/s_tanh.c
index ec8826f634..9048c977c1 100644
--- a/sysdeps/x86_64/fpu/multiarch/s_tanh.c
+++ b/sysdeps/x86_64/fpu/multiarch/s_tanh.c
@@ -25,10 +25,9 @@ extern double __redirect_tanh (double);
 # define SYMBOL_NAME tanh
 # include "ifunc-fma.h"
 
-libc_ifunc_redirected (__redirect_tanh, tanh, IFUNC_SELECTOR ());
+libc_ifunc_redirected (__redirect_tanh, __tanh, IFUNC_SELECTOR ());
+libm_alias_double (__tanh, tanh)
 
 # define __tanh __tanh_sse2
-# undef libm_alias_double
-# define libm_alias_double(a, b)
 #endif
 #include <sysdeps/ieee754/dbl-64/s_tanh.c>