[PATCH v5 6/6] loongarch: Enable THP-aligned load segments by default on 64-bit

[WANG Rui]

On LoongArch64 Linux, aligning ELF load segments to Transparent Huge Page
(THP) boundaries provides consistent performance benefits for large
binaries by reducing TLB pressure and improving instruction fetch
efficiency.

Enable THP-based load segment alignment by default on LoongArch64 by
setting `glibc.elf.hugetlb=1` during startup. Define the default THP
page size for load segment alignment on LoongArch64 as 32MB.

This allows the dynamic loader to apply THP-friendly alignment without
requiring the `glibc.elf.hugetlb` tunable to be explicitly set.

* sysdeps/unix/sysv/linux/loongarch/cpu-features.c
(init_cpu_features): Set glibc.elf.hugetlb to 1 by default on LoongArch64.
* sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h:
Define DL_MAP_DEFAULT_THP_PAGESIZE as 32MB.

Signed-off-by: WANG Rui <wangrui@loongson.cn>
---
 .../unix/sysv/linux/loongarch/cpu-features.c  |  6 +++++
 .../loongarch/lp64/dl-map-segment-align.h     | 22 +++++++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h

diff --git a/sysdeps/unix/sysv/linux/loongarch/cpu-features.c b/sysdeps/unix/sysv/linux/loongarch/cpu-features.c
index 0c125e64e2b..4da3f1ad4ee 100644
--- a/sysdeps/unix/sysv/linux/loongarch/cpu-features.c
+++ b/sysdeps/unix/sysv/linux/loongarch/cpu-features.c
@@ -27,4 +27,10 @@ init_cpu_features (struct cpu_features *cpu_features)
   GLRO(dl_larch_cpu_features).hwcap = GLRO(dl_hwcap);
   TUNABLE_GET (glibc, cpu, hwcaps, tunable_val_t *,
 	       TUNABLE_CALLBACK (set_hwcaps));
+
+#ifdef __LP64__
+  /* Enable THP-based load segment alignment by default on LoongArch64. */
+  if (!TUNABLE_IS_INITIALIZED (glibc, elf, hugetlb))
+    TUNABLE_SET (glibc, elf, hugetlb, 1);
+#endif
 }
diff --git a/sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h b/sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h
new file mode 100644
index 00000000000..c51ee4ac47e
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/loongarch/lp64/dl-map-segment-align.h
@@ -0,0 +1,22 @@
+/* _dl_map_segment_align.  LoongArch64 Linux version.
+   Copyright (C) 2026 Free Software Foundation, Inc.
+   Copyright The GNU Toolchain Authors.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#define DL_MAP_DEFAULT_THP_PAGESIZE (32 * 1024 * 1024)
+
+#include_next <dl-map-segment-align.h>
-- 
2.53.0