[llvm] [libc][bazel] Re-enable memcpy prefetching on x86. (PR #138945)

[Alexey Samsonov via llvm-commits]

https://github.com/vonosmas created https://github.com/llvm/llvm-project/pull/138945

It was re-enabled downstream after further performance analysis, so we can revert c65ed964657c93d51f3e05de9e0609419768a143, effectively re-landing the change.

>From 32513000ed4074cd7d50d27a9d78726088dd6752 Mon Sep 17 00:00:00 2001
From: Alexey Samsonov <vonosmas at gmail.com>
Date: Wed, 7 May 2025 12:25:58 -0700
Subject: [PATCH] [libc][bazel] Re-enable memcpy prefetching on x86.

It was re-enabled downstream after further performance analysis, so
we can revert c65ed964657c93d51f3e05de9e0609419768a143, effectively
re-landing the change.
---
 .../bazel/llvm-project-overlay/libc/libc_configure_options.bzl  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/utils/bazel/llvm-project-overlay/libc/libc_configure_options.bzl b/utils/bazel/llvm-project-overlay/libc/libc_configure_options.bzl
index f65da9e98226b..96d7fa86e9ddf 100644
--- a/utils/bazel/llvm-project-overlay/libc/libc_configure_options.bzl
+++ b/utils/bazel/llvm-project-overlay/libc/libc_configure_options.bzl
@@ -24,7 +24,7 @@ LIBC_CONFIGURE_OPTIONS = [
     # Documentation in libc/src/string/memory_utils/...
     # "LIBC_COPT_MEMCPY_USE_EMBEDDED_TINY",
     # "LIBC_COPT_MEMCPY_X86_USE_REPMOVSB_FROM_SIZE",
-    # "LIBC_COPT_MEMCPY_X86_USE_SOFTWARE_PREFETCHING",
+    "LIBC_COPT_MEMCPY_X86_USE_SOFTWARE_PREFETCHING",
     "LIBC_COPT_MEMSET_X86_USE_SOFTWARE_PREFETCHING",
 
     # Documentation in libc/docs/dev/printf_behavior.rst