[COMMITTED 2.36] Ensure calculations happen with desired rounding mode in y1lf128

[COMMITTED 2.36] Ensure calculations happen with desired rounding mode in y1lf128

[Aurelien Jarno]

From: Michael Hudson-Doyle <michael.hudson@canonical.com>

math/test-float128-y1 fails on x86_64 and ppc64el with gcc 12 and -O3,
because code inside a block guarded by SET_RESTORE_ROUNDL is being moved
after the rounding mode has been restored. Use math_force_eval to
prevent this (and insert some math_opt_barrier calls to prevent code
from being moved before the rounding mode is set).

Fixes #29463

Reviewed-By: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
(cherry picked from commit 2b274fd8c9c776cf70fcdb8356e678ada522a7b0)
---
 NEWS                             | 1 +
 sysdeps/ieee754/ldbl-128/e_j1l.c | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/NEWS b/NEWS
index 63e26d7062..bea1d8a11f 100644
--- a/NEWS
+++ b/NEWS
@@ -24,6 +24,7 @@ The following bugs are resolved with this release:
   [29446] _dlopen now ignores dl_caller argument in static mode
   [29485] Linux: Terminate subprocess on late failure in tst-pidfd
   [29490] alpha: New __brk_call implementation is broken
+  [29463] math/test-float128-y1 fails on x86_64
   [29528] elf: Call __libc_early_init for reused namespaces
   [29537] libc: [2.34 regression]: Alignment issue on m68k when using
   [29539] libc: LD_TRACE_LOADED_OBJECTS changed how vDSO library are
diff --git a/sysdeps/ieee754/ldbl-128/e_j1l.c b/sysdeps/ieee754/ldbl-128/e_j1l.c
index 54c457681a..9a9c5c6f00 100644
--- a/sysdeps/ieee754/ldbl-128/e_j1l.c
+++ b/sysdeps/ieee754/ldbl-128/e_j1l.c
@@ -869,10 +869,13 @@ __ieee754_y1l (_Float128 x)
     {
       /* 0 <= x <= 2 */
       SET_RESTORE_ROUNDL (FE_TONEAREST);
+      xx = math_opt_barrier (xx);
+      x = math_opt_barrier (x);
       z = xx * xx;
       p = xx * neval (z, Y0_2N, NY0_2N) / deval (z, Y0_2D, NY0_2D);
       p = -TWOOPI / xx + p;
       p = TWOOPI * __ieee754_logl (x) * __ieee754_j1l (x) + p;
+      math_force_eval (p);
       return p;
     }
 
-- 
2.35.1