[flang-commits] [libc] [compiler-rt] [clang-tools-extra] [clang] [flang] [libcxx] [llvm] Move implementation to src/string/memory_utils/x86_64/inline_memset.h and other minor changes (PR #71558)

via flang-commits flang-commits at lists.llvm.org
Tue Nov 7 08:38:34 PST 2023


https://github.com/doshimili updated https://github.com/llvm/llvm-project/pull/71558

>From 6c313955185c0d59564f6535b6f1580dca168bea Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Tue, 24 Oct 2023 21:15:23 +0000
Subject: [PATCH 01/16] Add software prefetching to memset

---
 libc/src/string/memory_utils/op_generic.h     | 19 +++++++++++++++++++
 .../memory_utils/x86_64/inline_memset.h       | 12 +++++++++++-
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index fd71ca30e24b936..54af7ea10e25e46 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -163,6 +163,25 @@ template <typename T> struct Memset {
     } while (offset < count - SIZE);
     tail(dst, value, count);
   }
+
+  template <size_t prefetch_distance, size_t prefetch_degree>
+  LIBC_INLINE static void loop_and_tail_prefetch(Ptr dst, uint8_t value,
+                                                 size_t count) {
+    Memset<uint512_t>::block(dst, value);
+    Memset<uint256_t>::block(dst + 64, value);
+    size_t offset = 96;
+    while (offset + prefetch_degree + kSize <= count) {
+      for (size_t i = 0; i < prefetch_degree / kCachelineSize; ++i)
+        PrefetchW(dst + offset + prefetch_distance + kCachelineSize * i);
+      for (size_t i = 0; i < prefetch_degree; i += kSize, offset += kSize)
+        block(dst + offset, value);
+    }
+    while (offset + kSize < count) {
+      block(dst + offset, value);
+      offset += kSize;
+    }
+    tail(dst, value, count);
+  }
 };
 
 template <typename T, typename... TS> struct MemsetSequence {
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index 6436594856b0eaf..da463bc0029f9aa 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -17,6 +17,11 @@
 
 namespace LIBC_NAMESPACE {
 
+static constexpr size_t kCachelineSize = 64;
+
+// prefetch for write
+static inline void PrefetchW(CPtr dst) { __builtin_prefetch(dst, 1, 3); }
+
 [[maybe_unused]] LIBC_INLINE static void
 inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
 #if defined(__AVX512F__)
@@ -53,12 +58,17 @@ inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
     return generic::Memset<uint128_t>::head_tail(dst, value, count);
   if (count <= 64)
     return generic::Memset<uint256_t>::head_tail(dst, value, count);
+  PrefetchW(dst + kCachelineSize);
   if (count <= 128)
     return generic::Memset<uint512_t>::head_tail(dst, value, count);
+  PrefetchW(dst + kCachelineSize * 2);
   // Aligned loop
   generic::Memset<uint256_t>::block(dst, value);
   align_to_next_boundary<32>(dst, count);
-  return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
+  if (count <= 192) {
+    return Memset<uint256_t>::loop_and_tail(dst, value, count);
+  }
+  return Memset<uint256_t>::loop_and_tail_prefetch<320, 128>(dst, value, count);
 }
 } // namespace LIBC_NAMESPACE
 

>From 15cbd0a0c851fa3ac5315e796bb69c1bf791e956 Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Tue, 24 Oct 2023 21:15:23 +0000
Subject: [PATCH 02/16] Add software prefetching to memset

---
 libc/src/string/CMakeLists.txt                |  1 +
 .../memory_utils/x86_64/inline_memset.h       | 32 ++++++++++++++++---
 .../llvm-project-overlay/libc/BUILD.bazel     |  1 +
 3 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/libc/src/string/CMakeLists.txt b/libc/src/string/CMakeLists.txt
index 67675b682081c67..aa69bff7a8cfada 100644
--- a/libc/src/string/CMakeLists.txt
+++ b/libc/src/string/CMakeLists.txt
@@ -656,6 +656,7 @@ if(${LIBC_TARGET_ARCHITECTURE_IS_X86})
   add_memset(memset_x86_64_opt_sse4   COMPILE_OPTIONS -march=nehalem        REQUIRE SSE4_2)
   add_memset(memset_x86_64_opt_avx2   COMPILE_OPTIONS -march=haswell        REQUIRE AVX2)
   add_memset(memset_x86_64_opt_avx512 COMPILE_OPTIONS -march=skylake-avx512 REQUIRE AVX512F)
+  add_memset(memset_x86_64_opt_sw_prefetch COMPILE_OPTIONS -DLIBC_COPT_MEMSET_X86_USE_SOFTWARE_PREFETCHING)
   add_memset(memset_opt_host          COMPILE_OPTIONS ${LIBC_COMPILE_OPTIONS_NATIVE})
   add_memset(memset)
 elseif(${LIBC_TARGET_ARCHITECTURE_IS_AARCH64})
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index da463bc0029f9aa..f3ad04930c52c64 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -16,12 +16,34 @@
 #include <stddef.h> // size_t
 
 namespace LIBC_NAMESPACE {
+namespace x86 {
 
 static constexpr size_t kCachelineSize = 64;
 
+LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetching =
+    LLVM_LIBC_IS_DEFINED(LIBC_COPT_MEMSET_X86_USE_SOFTWARE_PREFETCHING);
+
+} // namespace x86
+
 // prefetch for write
 static inline void PrefetchW(CPtr dst) { __builtin_prefetch(dst, 1, 3); }
 
+[[maybe_unused]] LIBC_INLINE static void inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
+  PrefetchW(dst + kCachelineSize);
+  if (count <= 128)
+    return generic::Memset<uint512_t>::head_tail(dst, value, count);
+  PrefetchW(dst + kCachelineSize * 2);
+  // Aligned loop
+  generic::Memset<uint256_t>::block(dst, value);
+  align_to_next_boundary<32>(dst, count);
+  if (count <= 192) {
+    return Memset<uint256_t>::loop_and_tail(dst, value, count);
+  }
+  else {
+    return Memset<uint256_t>::loop_and_tail_prefetch<320, 128>(dst, value, count);
+  }
+}
+
 [[maybe_unused]] LIBC_INLINE static void
 inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
 #if defined(__AVX512F__)
@@ -58,17 +80,17 @@ inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
     return generic::Memset<uint128_t>::head_tail(dst, value, count);
   if (count <= 64)
     return generic::Memset<uint256_t>::head_tail(dst, value, count);
-  PrefetchW(dst + kCachelineSize);
+  if constexpr (x86::kUseSoftwarePrefetching) {
+    return inline_memset_x86_sw_prefetching(dst, value, count);
+  }
   if (count <= 128)
     return generic::Memset<uint512_t>::head_tail(dst, value, count);
-  PrefetchW(dst + kCachelineSize * 2);
   // Aligned loop
   generic::Memset<uint256_t>::block(dst, value);
   align_to_next_boundary<32>(dst, count);
-  if (count <= 192) {
-    return Memset<uint256_t>::loop_and_tail(dst, value, count);
+  else {
+    return Memset<uint256_t>::loop_and_tail(dst, value, count); 
   }
-  return Memset<uint256_t>::loop_and_tail_prefetch<320, 128>(dst, value, count);
 }
 } // namespace LIBC_NAMESPACE
 
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 3ae68193dccd2b2..dea21fd77182605 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -33,6 +33,7 @@ PRINTF_COPTS = [
 MEMORY_COPTS = [
     # "LIBC_COPT_MEMCPY_X86_USE_REPMOVSB_FROM_SIZE=0",
     # "LIBC_COPT_MEMCPY_X86_USE_SOFTWARE_PREFETCHING",
+    # "LIBC_COPT_MEMSET_X86_USE_SOFTWARE_PREFETCHING",
 ]
 
 # A flag to pick which `mpfr` to use for math tests.

>From abb9debc49b7e171eae14a98320b9a49779c808c Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Fri, 27 Oct 2023 17:55:47 +0000
Subject: [PATCH 03/16] Fix formatting

---
 libc/src/string/memory_utils/x86_64/inline_memset.h | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index f3ad04930c52c64..e82b600bf66ab96 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -28,7 +28,8 @@ LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetching =
 // prefetch for write
 static inline void PrefetchW(CPtr dst) { __builtin_prefetch(dst, 1, 3); }
 
-[[maybe_unused]] LIBC_INLINE static void inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
+[[maybe_unused]] LIBC_INLINE static void
+inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
   PrefetchW(dst + kCachelineSize);
   if (count <= 128)
     return generic::Memset<uint512_t>::head_tail(dst, value, count);
@@ -38,9 +39,9 @@ static inline void PrefetchW(CPtr dst) { __builtin_prefetch(dst, 1, 3); }
   align_to_next_boundary<32>(dst, count);
   if (count <= 192) {
     return Memset<uint256_t>::loop_and_tail(dst, value, count);
-  }
-  else {
-    return Memset<uint256_t>::loop_and_tail_prefetch<320, 128>(dst, value, count);
+  } else {
+    return Memset<uint256_t>::loop_and_tail_prefetch<320, 128>(dst, value,
+                                                               count);
   }
 }
 
@@ -89,7 +90,7 @@ inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
   generic::Memset<uint256_t>::block(dst, value);
   align_to_next_boundary<32>(dst, count);
   else {
-    return Memset<uint256_t>::loop_and_tail(dst, value, count); 
+    return Memset<uint256_t>::loop_and_tail(dst, value, count);
   }
 }
 } // namespace LIBC_NAMESPACE

>From 2155db70066c2c220160c4178bd73237e1372d45 Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Mon, 30 Oct 2023 14:53:56 +0000
Subject: [PATCH 04/16] Fix build errors

---
 libc/src/string/memory_utils/op_generic.h         | 15 +++++++++------
 .../string/memory_utils/x86_64/inline_memset.h    |  7 ++-----
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index 54af7ea10e25e46..4ba137c97ec9a9a 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -87,6 +87,9 @@ template <class T, size_t N>
 struct array_size<cpp::array<T, N>> : cpp::integral_constant<size_t, N> {};
 template <typename T> constexpr size_t array_size_v = array_size<T>::value;
 
+// Size of a cacheline for software prefetching
+static constexpr size_t kCachelineSize = 64;
+
 // Generic operations for the above type categories.
 
 template <typename T> T load(CPtr src) {
@@ -167,18 +170,18 @@ template <typename T> struct Memset {
   template <size_t prefetch_distance, size_t prefetch_degree>
   LIBC_INLINE static void loop_and_tail_prefetch(Ptr dst, uint8_t value,
                                                  size_t count) {
-    Memset<uint512_t>::block(dst, value);
-    Memset<uint256_t>::block(dst + 64, value);
+    Memset<64>::block(dst, value);
+    Memset<32>::block(dst + 64, value);
     size_t offset = 96;
-    while (offset + prefetch_degree + kSize <= count) {
+    while (offset + prefetch_degree + SIZE <= count) {
       for (size_t i = 0; i < prefetch_degree / kCachelineSize; ++i)
         PrefetchW(dst + offset + prefetch_distance + kCachelineSize * i);
-      for (size_t i = 0; i < prefetch_degree; i += kSize, offset += kSize)
+      for (size_t i = 0; i < prefetch_degree; i += SIZE, offset += SIZE)
         block(dst + offset, value);
     }
-    while (offset + kSize < count) {
+    while (offset + SIZE < count) {
       block(dst + offset, value);
-      offset += kSize;
+      offset += SIZE;
     }
     tail(dst, value, count);
   }
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index e82b600bf66ab96..fca48e9658a752d 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -17,9 +17,6 @@
 
 namespace LIBC_NAMESPACE {
 namespace x86 {
-
-static constexpr size_t kCachelineSize = 64;
-
 LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetching =
     LLVM_LIBC_IS_DEFINED(LIBC_COPT_MEMSET_X86_USE_SOFTWARE_PREFETCHING);
 
@@ -30,10 +27,10 @@ static inline void PrefetchW(CPtr dst) { __builtin_prefetch(dst, 1, 3); }
 
 [[maybe_unused]] LIBC_INLINE static void
 inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
-  PrefetchW(dst + kCachelineSize);
+  PrefetchW(dst + generic::kCachelineSize);
   if (count <= 128)
     return generic::Memset<uint512_t>::head_tail(dst, value, count);
-  PrefetchW(dst + kCachelineSize * 2);
+  PrefetchW(dst + generic::kCachelineSize * 2);
   // Aligned loop
   generic::Memset<uint256_t>::block(dst, value);
   align_to_next_boundary<32>(dst, count);

>From 9fe0041c2bb8ba1d522538c79ac1ebae7d0632bb Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Mon, 30 Oct 2023 17:09:15 +0000
Subject: [PATCH 05/16] Fix build errors

---
 libc/src/string/memory_utils/op_generic.h     | 15 +++---
 .../memory_utils/x86_64/inline_memset.h       | 50 +++++++++----------
 2 files changed, 33 insertions(+), 32 deletions(-)

diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index 4ba137c97ec9a9a..12eeb65a1edc52e 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -48,6 +48,13 @@ using generic_v256 = uint8_t __attribute__((__vector_size__(32)));
 using generic_v512 = uint8_t __attribute__((__vector_size__(64)));
 } // namespace LIBC_NAMESPACE
 
+namespace sw_prefetch {
+  // Size of a cacheline for software prefetching
+static constexpr size_t kCachelineSize = 64;
+  // prefetch for write
+static inline void PrefetchW(CPtr dst) { __builtin_prefetch(dst, 1, 3); }
+}
+
 namespace LIBC_NAMESPACE::generic {
 
 // We accept three types of values as elements for generic operations:
@@ -87,9 +94,6 @@ template <class T, size_t N>
 struct array_size<cpp::array<T, N>> : cpp::integral_constant<size_t, N> {};
 template <typename T> constexpr size_t array_size_v = array_size<T>::value;
 
-// Size of a cacheline for software prefetching
-static constexpr size_t kCachelineSize = 64;
-
 // Generic operations for the above type categories.
 
 template <typename T> T load(CPtr src) {
@@ -167,12 +171,9 @@ template <typename T> struct Memset {
     tail(dst, value, count);
   }
 
-  template <size_t prefetch_distance, size_t prefetch_degree>
+  template <size_t prefetch_distance, size_t prefetch_degree, size_t offset>
   LIBC_INLINE static void loop_and_tail_prefetch(Ptr dst, uint8_t value,
                                                  size_t count) {
-    Memset<64>::block(dst, value);
-    Memset<32>::block(dst + 64, value);
-    size_t offset = 96;
     while (offset + prefetch_degree + SIZE <= count) {
       for (size_t i = 0; i < prefetch_degree / kCachelineSize; ++i)
         PrefetchW(dst + offset + prefetch_distance + kCachelineSize * i);
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index fca48e9658a752d..bc7a6162f77b9cd 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -17,33 +17,11 @@
 
 namespace LIBC_NAMESPACE {
 namespace x86 {
-LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetching =
+LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetchingMemset =
     LLVM_LIBC_IS_DEFINED(LIBC_COPT_MEMSET_X86_USE_SOFTWARE_PREFETCHING);
 
 } // namespace x86
 
-// prefetch for write
-static inline void PrefetchW(CPtr dst) { __builtin_prefetch(dst, 1, 3); }
-
-[[maybe_unused]] LIBC_INLINE static void
-inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
-  PrefetchW(dst + generic::kCachelineSize);
-  if (count <= 128)
-    return generic::Memset<uint512_t>::head_tail(dst, value, count);
-  PrefetchW(dst + generic::kCachelineSize * 2);
-  // Aligned loop
-  generic::Memset<uint256_t>::block(dst, value);
-  align_to_next_boundary<32>(dst, count);
-  if (count <= 192) {
-    return Memset<uint256_t>::loop_and_tail(dst, value, count);
-  } else {
-    return Memset<uint256_t>::loop_and_tail_prefetch<320, 128>(dst, value,
-                                                               count);
-  }
-}
-
-[[maybe_unused]] LIBC_INLINE static void
-inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
 #if defined(__AVX512F__)
   using uint128_t = generic_v128;
   using uint256_t = generic_v256;
@@ -62,6 +40,28 @@ inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
   using uint512_t = cpp::array<uint64_t, 8>;
 #endif
 
+[[maybe_unused]] LIBC_INLINE static void
+inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
+  sw_prefetch::PrefetchW(dst + generic::kCachelineSize);
+  if (count <= 128)
+    return generic::Memset<uint512_t>::head_tail(dst, value, count);
+  sw_prefetch::PrefetchW(dst + generic::kCachelineSize * 2);
+  // Aligned loop
+  generic::Memset<uint256_t>::block(dst, value);
+  align_to_next_boundary<32>(dst, count);
+  if (count <= 192) {
+    return Memset<uint256_t>::loop_and_tail(dst, value, count);
+  } else {
+    // Warm up memset
+    generic::Memset<uint256_t>::block(dst, value);
+    generic::Memset<uint128_t>::block(dst + 64, value);
+    return generic::Memset<uint256_t>::loop_and_tail_prefetch<320, 128, 96>(dst, value,
+                                                               count);
+  }
+}
+
+[[maybe_unused]] LIBC_INLINE static void
+inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
   if (count == 0)
     return;
   if (count == 1)
@@ -78,7 +78,7 @@ inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
     return generic::Memset<uint128_t>::head_tail(dst, value, count);
   if (count <= 64)
     return generic::Memset<uint256_t>::head_tail(dst, value, count);
-  if constexpr (x86::kUseSoftwarePrefetching) {
+  if constexpr (x86::kUseSoftwarePrefetchingMemset) {
     return inline_memset_x86_sw_prefetching(dst, value, count);
   }
   if (count <= 128)
@@ -87,7 +87,7 @@ inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
   generic::Memset<uint256_t>::block(dst, value);
   align_to_next_boundary<32>(dst, count);
   else {
-    return Memset<uint256_t>::loop_and_tail(dst, value, count);
+    return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
   }
 }
 } // namespace LIBC_NAMESPACE

>From 52aad858a4a8652f95a3e1120e4dd7bd2f45d225 Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Mon, 30 Oct 2023 17:39:04 +0000
Subject: [PATCH 06/16] Fix formatting

---
 libc/src/string/memory_utils/op_generic.h     |  6 +-
 .../memory_utils/x86_64/inline_memset.h       | 92 +++++++++----------
 2 files changed, 49 insertions(+), 49 deletions(-)

diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index 12eeb65a1edc52e..af6a814be1542a4 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -49,11 +49,11 @@ using generic_v512 = uint8_t __attribute__((__vector_size__(64)));
 } // namespace LIBC_NAMESPACE
 
 namespace sw_prefetch {
-  // Size of a cacheline for software prefetching
+// Size of a cacheline for software prefetching
 static constexpr size_t kCachelineSize = 64;
-  // prefetch for write
+// prefetch for write
 static inline void PrefetchW(CPtr dst) { __builtin_prefetch(dst, 1, 3); }
-}
+} // namespace sw_prefetch
 
 namespace LIBC_NAMESPACE::generic {
 
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index bc7a6162f77b9cd..9000aa03019d291 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -40,56 +40,56 @@ LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetchingMemset =
   using uint512_t = cpp::array<uint64_t, 8>;
 #endif
 
-[[maybe_unused]] LIBC_INLINE static void
-inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
-  sw_prefetch::PrefetchW(dst + generic::kCachelineSize);
-  if (count <= 128)
-    return generic::Memset<uint512_t>::head_tail(dst, value, count);
-  sw_prefetch::PrefetchW(dst + generic::kCachelineSize * 2);
-  // Aligned loop
-  generic::Memset<uint256_t>::block(dst, value);
-  align_to_next_boundary<32>(dst, count);
-  if (count <= 192) {
-    return Memset<uint256_t>::loop_and_tail(dst, value, count);
-  } else {
-    // Warm up memset
+  [[maybe_unused]] LIBC_INLINE static void
+  inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
+    sw_prefetch::PrefetchW(dst + generic::kCachelineSize);
+    if (count <= 128)
+      return generic::Memset<uint512_t>::head_tail(dst, value, count);
+    sw_prefetch::PrefetchW(dst + generic::kCachelineSize * 2);
+    // Aligned loop
     generic::Memset<uint256_t>::block(dst, value);
-    generic::Memset<uint128_t>::block(dst + 64, value);
-    return generic::Memset<uint256_t>::loop_and_tail_prefetch<320, 128, 96>(dst, value,
-                                                               count);
+    align_to_next_boundary<32>(dst, count);
+    if (count <= 192) {
+      return Memset<uint256_t>::loop_and_tail(dst, value, count);
+    } else {
+      // Warm up memset
+      generic::Memset<uint256_t>::block(dst, value);
+      generic::Memset<uint128_t>::block(dst + 64, value);
+      return generic::Memset<uint256_t>::loop_and_tail_prefetch<320, 128, 96>(
+          dst, value, count);
+    }
   }
-}
 
-[[maybe_unused]] LIBC_INLINE static void
-inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
-  if (count == 0)
-    return;
-  if (count == 1)
-    return generic::Memset<uint8_t>::block(dst, value);
-  if (count == 2)
-    return generic::Memset<uint16_t>::block(dst, value);
-  if (count == 3)
-    return generic::MemsetSequence<uint16_t, uint8_t>::block(dst, value);
-  if (count <= 8)
-    return generic::Memset<uint32_t>::head_tail(dst, value, count);
-  if (count <= 16)
-    return generic::Memset<uint64_t>::head_tail(dst, value, count);
-  if (count <= 32)
-    return generic::Memset<uint128_t>::head_tail(dst, value, count);
-  if (count <= 64)
-    return generic::Memset<uint256_t>::head_tail(dst, value, count);
-  if constexpr (x86::kUseSoftwarePrefetchingMemset) {
-    return inline_memset_x86_sw_prefetching(dst, value, count);
-  }
-  if (count <= 128)
-    return generic::Memset<uint512_t>::head_tail(dst, value, count);
-  // Aligned loop
-  generic::Memset<uint256_t>::block(dst, value);
-  align_to_next_boundary<32>(dst, count);
-  else {
-    return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
+  [[maybe_unused]] LIBC_INLINE static void
+  inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
+    if (count == 0)
+      return;
+    if (count == 1)
+      return generic::Memset<uint8_t>::block(dst, value);
+    if (count == 2)
+      return generic::Memset<uint16_t>::block(dst, value);
+    if (count == 3)
+      return generic::MemsetSequence<uint16_t, uint8_t>::block(dst, value);
+    if (count <= 8)
+      return generic::Memset<uint32_t>::head_tail(dst, value, count);
+    if (count <= 16)
+      return generic::Memset<uint64_t>::head_tail(dst, value, count);
+    if (count <= 32)
+      return generic::Memset<uint128_t>::head_tail(dst, value, count);
+    if (count <= 64)
+      return generic::Memset<uint256_t>::head_tail(dst, value, count);
+    if constexpr (x86::kUseSoftwarePrefetchingMemset) {
+      return inline_memset_x86_sw_prefetching(dst, value, count);
+    }
+    if (count <= 128)
+      return generic::Memset<uint512_t>::head_tail(dst, value, count);
+    // Aligned loop
+    generic::Memset<uint256_t>::block(dst, value);
+    align_to_next_boundary<32>(dst, count);
+    else {
+      return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
+    }
   }
-}
 } // namespace LIBC_NAMESPACE
 
 #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_X86_64_INLINE_MEMSET_H

>From efbfcd19cecbd3e27b72523d06d8cff3a5bbbafa Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Mon, 30 Oct 2023 19:12:19 +0000
Subject: [PATCH 07/16] Fix formatting

---
 libc/src/string/memory_utils/op_generic.h     | 24 +++++++++++--------
 .../memory_utils/x86_64/inline_memset.h       |  6 ++---
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index af6a814be1542a4..ae221e0fa380655 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -48,12 +48,12 @@ using generic_v256 = uint8_t __attribute__((__vector_size__(32)));
 using generic_v512 = uint8_t __attribute__((__vector_size__(64)));
 } // namespace LIBC_NAMESPACE
 
-namespace sw_prefetch {
+namespace LIBC_NAMESPACE::sw_prefetch {
 // Size of a cacheline for software prefetching
 static constexpr size_t kCachelineSize = 64;
 // prefetch for write
 static inline void PrefetchW(CPtr dst) { __builtin_prefetch(dst, 1, 3); }
-} // namespace sw_prefetch
+} // namespace LIBC_NAMESPACE::sw_prefetch
 
 namespace LIBC_NAMESPACE::generic {
 
@@ -174,15 +174,19 @@ template <typename T> struct Memset {
   template <size_t prefetch_distance, size_t prefetch_degree, size_t offset>
   LIBC_INLINE static void loop_and_tail_prefetch(Ptr dst, uint8_t value,
                                                  size_t count) {
-    while (offset + prefetch_degree + SIZE <= count) {
-      for (size_t i = 0; i < prefetch_degree / kCachelineSize; ++i)
-        PrefetchW(dst + offset + prefetch_distance + kCachelineSize * i);
-      for (size_t i = 0; i < prefetch_degree; i += SIZE, offset += SIZE)
-        block(dst + offset, value);
+    size_t prefetch_offset = offset;
+
+    while (prefetch_offset + prefetch_degree + SIZE <= count) {
+      for (size_t i = 0; i < prefetch_degree / sw_prefetch::kCachelineSize; ++i)
+        PrefetchW(dst + prefetch_offset + prefetch_distance +
+                  sw_prefetch::kCachelineSize * i);
+      for (size_t i = 0; i < prefetch_degree;
+           i += SIZE, prefetch_offset += SIZE)
+        block(dst + prefetch_offset, value);
     }
-    while (offset + SIZE < count) {
-      block(dst + offset, value);
-      offset += SIZE;
+    while (prefetch_offset + SIZE < count) {
+      block(dst + prefetch_offset, value);
+      prefetch_offset += SIZE;
     }
     tail(dst, value, count);
   }
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index 9000aa03019d291..fc00f86fc0fb34e 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -42,15 +42,15 @@ LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetchingMemset =
 
   [[maybe_unused]] LIBC_INLINE static void
   inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
-    sw_prefetch::PrefetchW(dst + generic::kCachelineSize);
+    sw_prefetch::PrefetchW(dst + sw_prefetch::kCachelineSize);
     if (count <= 128)
       return generic::Memset<uint512_t>::head_tail(dst, value, count);
-    sw_prefetch::PrefetchW(dst + generic::kCachelineSize * 2);
+    sw_prefetch::PrefetchW(dst + sw_prefetch::kCachelineSize * 2);
     // Aligned loop
     generic::Memset<uint256_t>::block(dst, value);
     align_to_next_boundary<32>(dst, count);
     if (count <= 192) {
-      return Memset<uint256_t>::loop_and_tail(dst, value, count);
+      return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
     } else {
       // Warm up memset
       generic::Memset<uint256_t>::block(dst, value);

>From d97c8c0d17c860a892c029059469b70962e4a201 Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Mon, 30 Oct 2023 20:21:49 +0000
Subject: [PATCH 08/16] Fix formatting

---
 libc/src/string/memory_utils/op_generic.h           | 4 ++--
 libc/src/string/memory_utils/x86_64/inline_memset.h | 4 +---
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index ae221e0fa380655..35f74b544bb3598 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -178,8 +178,8 @@ template <typename T> struct Memset {
 
     while (prefetch_offset + prefetch_degree + SIZE <= count) {
       for (size_t i = 0; i < prefetch_degree / sw_prefetch::kCachelineSize; ++i)
-        PrefetchW(dst + prefetch_offset + prefetch_distance +
-                  sw_prefetch::kCachelineSize * i);
+        sw_prefetch::PrefetchW(dst + prefetch_offset + prefetch_distance +
+                               sw_prefetch::kCachelineSize * i);
       for (size_t i = 0; i < prefetch_degree;
            i += SIZE, prefetch_offset += SIZE)
         block(dst + prefetch_offset, value);
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index fc00f86fc0fb34e..50ba2fb2e37cfab 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -86,9 +86,7 @@ LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetchingMemset =
     // Aligned loop
     generic::Memset<uint256_t>::block(dst, value);
     align_to_next_boundary<32>(dst, count);
-    else {
-      return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
-    }
+    return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
   }
 } // namespace LIBC_NAMESPACE
 

>From 34d572e81b561b4450022dc358f6e3a91632224f Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Mon, 30 Oct 2023 20:21:49 +0000
Subject: [PATCH 09/16] Fix formatting

---
 libc/src/string/memory_utils/op_generic.h      | 18 +++++++++---------
 .../string/memory_utils/x86_64/inline_memset.h |  5 +----
 2 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index 35f74b544bb3598..f36c3acafff5665 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -171,22 +171,22 @@ template <typename T> struct Memset {
     tail(dst, value, count);
   }
 
-  template <size_t prefetch_distance, size_t prefetch_degree, size_t offset>
+  template <size_t prefetch_distance, size_t prefetch_degree>
   LIBC_INLINE static void loop_and_tail_prefetch(Ptr dst, uint8_t value,
                                                  size_t count) {
-    size_t prefetch_offset = offset;
+    size_t offset = 0;
 
-    while (prefetch_offset + prefetch_degree + SIZE <= count) {
+    while (offset + prefetch_degree + SIZE <= count) {
       for (size_t i = 0; i < prefetch_degree / sw_prefetch::kCachelineSize; ++i)
-        sw_prefetch::PrefetchW(dst + prefetch_offset + prefetch_distance +
+        sw_prefetch::PrefetchW(dst + offset + prefetch_distance +
                                sw_prefetch::kCachelineSize * i);
       for (size_t i = 0; i < prefetch_degree;
-           i += SIZE, prefetch_offset += SIZE)
-        block(dst + prefetch_offset, value);
+           i += SIZE, offset += SIZE)
+        block(dst + offset, value);
     }
-    while (prefetch_offset + SIZE < count) {
-      block(dst + prefetch_offset, value);
-      prefetch_offset += SIZE;
+    while (offset + SIZE < count) {
+      block(dst + offset, value);
+      offset += SIZE;
     }
     tail(dst, value, count);
   }
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index 50ba2fb2e37cfab..4834968c0b99f38 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -52,10 +52,7 @@ LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetchingMemset =
     if (count <= 192) {
       return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
     } else {
-      // Warm up memset
-      generic::Memset<uint256_t>::block(dst, value);
-      generic::Memset<uint128_t>::block(dst + 64, value);
-      return generic::Memset<uint256_t>::loop_and_tail_prefetch<320, 128, 96>(
+      return generic::Memset<uint256_t>::loop_and_tail_prefetch<320, 128>(
           dst, value, count);
     }
   }

>From f363ce21eedc44821e5163ad9472396856a096c1 Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Mon, 30 Oct 2023 20:21:49 +0000
Subject: [PATCH 10/16] Fix formatting

---
 libc/src/string/memory_utils/op_generic.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index f36c3acafff5665..4063de1d5f5832a 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -180,8 +180,7 @@ template <typename T> struct Memset {
       for (size_t i = 0; i < prefetch_degree / sw_prefetch::kCachelineSize; ++i)
         sw_prefetch::PrefetchW(dst + offset + prefetch_distance +
                                sw_prefetch::kCachelineSize * i);
-      for (size_t i = 0; i < prefetch_degree;
-           i += SIZE, offset += SIZE)
+      for (size_t i = 0; i < prefetch_degree; i += SIZE, offset += SIZE)
         block(dst + offset, value);
     }
     while (offset + SIZE < count) {

>From 1110c4e6237dcae26351d7678ee91de0e7fe3791 Mon Sep 17 00:00:00 2001
From: doshimili <milidoshi at google.com>
Date: Tue, 31 Oct 2023 15:42:32 -0400
Subject: [PATCH 11/16] Sw prefetch in memset (#2)

* Add software prefetching to memset

* Add software prefetching to memset

* Fix formatting

* Fix build errors

* Fix build errors

* Fix formatting

* Fix formatting

* Fix formatting

* Fix formatting

* Fix formatting
---
 libc/src/string/CMakeLists.txt                |  1 +
 libc/src/string/memory_utils/op_generic.h     | 26 +++++++
 .../memory_utils/x86_64/inline_memset.h       | 75 ++++++++++++-------
 .../llvm-project-overlay/libc/BUILD.bazel     |  1 +
 4 files changed, 78 insertions(+), 25 deletions(-)

diff --git a/libc/src/string/CMakeLists.txt b/libc/src/string/CMakeLists.txt
index 67675b682081c67..aa69bff7a8cfada 100644
--- a/libc/src/string/CMakeLists.txt
+++ b/libc/src/string/CMakeLists.txt
@@ -656,6 +656,7 @@ if(${LIBC_TARGET_ARCHITECTURE_IS_X86})
   add_memset(memset_x86_64_opt_sse4   COMPILE_OPTIONS -march=nehalem        REQUIRE SSE4_2)
   add_memset(memset_x86_64_opt_avx2   COMPILE_OPTIONS -march=haswell        REQUIRE AVX2)
   add_memset(memset_x86_64_opt_avx512 COMPILE_OPTIONS -march=skylake-avx512 REQUIRE AVX512F)
+  add_memset(memset_x86_64_opt_sw_prefetch COMPILE_OPTIONS -DLIBC_COPT_MEMSET_X86_USE_SOFTWARE_PREFETCHING)
   add_memset(memset_opt_host          COMPILE_OPTIONS ${LIBC_COMPILE_OPTIONS_NATIVE})
   add_memset(memset)
 elseif(${LIBC_TARGET_ARCHITECTURE_IS_AARCH64})
diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index fd71ca30e24b936..4063de1d5f5832a 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -48,6 +48,13 @@ using generic_v256 = uint8_t __attribute__((__vector_size__(32)));
 using generic_v512 = uint8_t __attribute__((__vector_size__(64)));
 } // namespace LIBC_NAMESPACE
 
+namespace LIBC_NAMESPACE::sw_prefetch {
+// Size of a cacheline for software prefetching
+static constexpr size_t kCachelineSize = 64;
+// prefetch for write
+static inline void PrefetchW(CPtr dst) { __builtin_prefetch(dst, 1, 3); }
+} // namespace LIBC_NAMESPACE::sw_prefetch
+
 namespace LIBC_NAMESPACE::generic {
 
 // We accept three types of values as elements for generic operations:
@@ -163,6 +170,25 @@ template <typename T> struct Memset {
     } while (offset < count - SIZE);
     tail(dst, value, count);
   }
+
+  template <size_t prefetch_distance, size_t prefetch_degree>
+  LIBC_INLINE static void loop_and_tail_prefetch(Ptr dst, uint8_t value,
+                                                 size_t count) {
+    size_t offset = 0;
+
+    while (offset + prefetch_degree + SIZE <= count) {
+      for (size_t i = 0; i < prefetch_degree / sw_prefetch::kCachelineSize; ++i)
+        sw_prefetch::PrefetchW(dst + offset + prefetch_distance +
+                               sw_prefetch::kCachelineSize * i);
+      for (size_t i = 0; i < prefetch_degree; i += SIZE, offset += SIZE)
+        block(dst + offset, value);
+    }
+    while (offset + SIZE < count) {
+      block(dst + offset, value);
+      offset += SIZE;
+    }
+    tail(dst, value, count);
+  }
 };
 
 template <typename T, typename... TS> struct MemsetSequence {
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index 6436594856b0eaf..4834968c0b99f38 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -16,9 +16,12 @@
 #include <stddef.h> // size_t
 
 namespace LIBC_NAMESPACE {
+namespace x86 {
+LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetchingMemset =
+    LLVM_LIBC_IS_DEFINED(LIBC_COPT_MEMSET_X86_USE_SOFTWARE_PREFETCHING);
+
+} // namespace x86
 
-[[maybe_unused]] LIBC_INLINE static void
-inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
 #if defined(__AVX512F__)
   using uint128_t = generic_v128;
   using uint256_t = generic_v256;
@@ -37,29 +40,51 @@ inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
   using uint512_t = cpp::array<uint64_t, 8>;
 #endif
 
-  if (count == 0)
-    return;
-  if (count == 1)
-    return generic::Memset<uint8_t>::block(dst, value);
-  if (count == 2)
-    return generic::Memset<uint16_t>::block(dst, value);
-  if (count == 3)
-    return generic::MemsetSequence<uint16_t, uint8_t>::block(dst, value);
-  if (count <= 8)
-    return generic::Memset<uint32_t>::head_tail(dst, value, count);
-  if (count <= 16)
-    return generic::Memset<uint64_t>::head_tail(dst, value, count);
-  if (count <= 32)
-    return generic::Memset<uint128_t>::head_tail(dst, value, count);
-  if (count <= 64)
-    return generic::Memset<uint256_t>::head_tail(dst, value, count);
-  if (count <= 128)
-    return generic::Memset<uint512_t>::head_tail(dst, value, count);
-  // Aligned loop
-  generic::Memset<uint256_t>::block(dst, value);
-  align_to_next_boundary<32>(dst, count);
-  return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
-}
+  [[maybe_unused]] LIBC_INLINE static void
+  inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
+    sw_prefetch::PrefetchW(dst + sw_prefetch::kCachelineSize);
+    if (count <= 128)
+      return generic::Memset<uint512_t>::head_tail(dst, value, count);
+    sw_prefetch::PrefetchW(dst + sw_prefetch::kCachelineSize * 2);
+    // Aligned loop
+    generic::Memset<uint256_t>::block(dst, value);
+    align_to_next_boundary<32>(dst, count);
+    if (count <= 192) {
+      return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
+    } else {
+      return generic::Memset<uint256_t>::loop_and_tail_prefetch<320, 128>(
+          dst, value, count);
+    }
+  }
+
+  [[maybe_unused]] LIBC_INLINE static void
+  inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
+    if (count == 0)
+      return;
+    if (count == 1)
+      return generic::Memset<uint8_t>::block(dst, value);
+    if (count == 2)
+      return generic::Memset<uint16_t>::block(dst, value);
+    if (count == 3)
+      return generic::MemsetSequence<uint16_t, uint8_t>::block(dst, value);
+    if (count <= 8)
+      return generic::Memset<uint32_t>::head_tail(dst, value, count);
+    if (count <= 16)
+      return generic::Memset<uint64_t>::head_tail(dst, value, count);
+    if (count <= 32)
+      return generic::Memset<uint128_t>::head_tail(dst, value, count);
+    if (count <= 64)
+      return generic::Memset<uint256_t>::head_tail(dst, value, count);
+    if constexpr (x86::kUseSoftwarePrefetchingMemset) {
+      return inline_memset_x86_sw_prefetching(dst, value, count);
+    }
+    if (count <= 128)
+      return generic::Memset<uint512_t>::head_tail(dst, value, count);
+    // Aligned loop
+    generic::Memset<uint256_t>::block(dst, value);
+    align_to_next_boundary<32>(dst, count);
+    return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
+  }
 } // namespace LIBC_NAMESPACE
 
 #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_X86_64_INLINE_MEMSET_H
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 3ae68193dccd2b2..dea21fd77182605 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -33,6 +33,7 @@ PRINTF_COPTS = [
 MEMORY_COPTS = [
     # "LIBC_COPT_MEMCPY_X86_USE_REPMOVSB_FROM_SIZE=0",
     # "LIBC_COPT_MEMCPY_X86_USE_SOFTWARE_PREFETCHING",
+    # "LIBC_COPT_MEMSET_X86_USE_SOFTWARE_PREFETCHING",
 ]
 
 # A flag to pick which `mpfr` to use for math tests.

>From 6c96e79b76f2a09f908af1fc323b7986e871ceec Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Tue, 31 Oct 2023 20:35:35 +0000
Subject: [PATCH 12/16] Add warmup to memset

---
 libc/src/string/memory_utils/op_generic.h           | 3 +--
 libc/src/string/memory_utils/x86_64/inline_memset.h | 4 ++++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index 4063de1d5f5832a..2844501a7459044 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -174,8 +174,7 @@ template <typename T> struct Memset {
   template <size_t prefetch_distance, size_t prefetch_degree>
   LIBC_INLINE static void loop_and_tail_prefetch(Ptr dst, uint8_t value,
                                                  size_t count) {
-    size_t offset = 0;
-
+    size_t offset = 96;
     while (offset + prefetch_degree + SIZE <= count) {
       for (size_t i = 0; i < prefetch_degree / sw_prefetch::kCachelineSize; ++i)
         sw_prefetch::PrefetchW(dst + offset + prefetch_distance +
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index 4834968c0b99f38..98f559bca875a3a 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -42,9 +42,11 @@ LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetchingMemset =
 
   [[maybe_unused]] LIBC_INLINE static void
   inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
+    // Prefetch one cacheline
     sw_prefetch::PrefetchW(dst + sw_prefetch::kCachelineSize);
     if (count <= 128)
       return generic::Memset<uint512_t>::head_tail(dst, value, count);
+    // Prefetch the next cacheline
     sw_prefetch::PrefetchW(dst + sw_prefetch::kCachelineSize * 2);
     // Aligned loop
     generic::Memset<uint256_t>::block(dst, value);
@@ -52,6 +54,8 @@ LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetchingMemset =
     if (count <= 192) {
       return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
     } else {
+      generic::Memset<uint512_t>::block(dst, value);
+      generic::Memset<uint256_t>::block(dst + sizeof(uint512_t), value);
       return generic::Memset<uint256_t>::loop_and_tail_prefetch<320, 128>(
           dst, value, count);
     }

>From 01be692503dc4e913b00b5d074b2cbb4c63347f6 Mon Sep 17 00:00:00 2001
From: doshimili <milidoshi at google.com>
Date: Tue, 31 Oct 2023 17:05:57 -0400
Subject: [PATCH 13/16] Add software prefetch instructions to memset

* Add software prefetching to memset

* Add software prefetching to memset

* Fix formatting

* Fix build errors

* Fix build errors

* Fix formatting

* Fix formatting

* Fix formatting

* Fix formatting

* Fix formatting

* Add warmup to memset
---
 libc/src/string/memory_utils/op_generic.h           | 3 +--
 libc/src/string/memory_utils/x86_64/inline_memset.h | 4 ++++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index 4063de1d5f5832a..2844501a7459044 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -174,8 +174,7 @@ template <typename T> struct Memset {
   template <size_t prefetch_distance, size_t prefetch_degree>
   LIBC_INLINE static void loop_and_tail_prefetch(Ptr dst, uint8_t value,
                                                  size_t count) {
-    size_t offset = 0;
-
+    size_t offset = 96;
     while (offset + prefetch_degree + SIZE <= count) {
       for (size_t i = 0; i < prefetch_degree / sw_prefetch::kCachelineSize; ++i)
         sw_prefetch::PrefetchW(dst + offset + prefetch_distance +
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index 4834968c0b99f38..98f559bca875a3a 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -42,9 +42,11 @@ LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetchingMemset =
 
   [[maybe_unused]] LIBC_INLINE static void
   inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
+    // Prefetch one cacheline
     sw_prefetch::PrefetchW(dst + sw_prefetch::kCachelineSize);
     if (count <= 128)
       return generic::Memset<uint512_t>::head_tail(dst, value, count);
+    // Prefetch the next cacheline
     sw_prefetch::PrefetchW(dst + sw_prefetch::kCachelineSize * 2);
     // Aligned loop
     generic::Memset<uint256_t>::block(dst, value);
@@ -52,6 +54,8 @@ LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetchingMemset =
     if (count <= 192) {
       return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
     } else {
+      generic::Memset<uint512_t>::block(dst, value);
+      generic::Memset<uint256_t>::block(dst + sizeof(uint512_t), value);
       return generic::Memset<uint256_t>::loop_and_tail_prefetch<320, 128>(
           dst, value, count);
     }

>From 2f3f80163438cd663eed98b63fd0b704a38315b8 Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Tue, 31 Oct 2023 21:10:17 +0000
Subject: [PATCH 14/16] SW Prefetching in Memset

---
 libc/src/string/memory_utils/x86_64/inline_memset.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index 98f559bca875a3a..e4eadf614adc6bf 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -46,7 +46,7 @@ LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetchingMemset =
     sw_prefetch::PrefetchW(dst + sw_prefetch::kCachelineSize);
     if (count <= 128)
       return generic::Memset<uint512_t>::head_tail(dst, value, count);
-    // Prefetch the next cacheline
+    // Prefetch the second cacheline
     sw_prefetch::PrefetchW(dst + sw_prefetch::kCachelineSize * 2);
     // Aligned loop
     generic::Memset<uint256_t>::block(dst, value);

>From 24467d08dd39a286629e6fb4bcc3c8d0fede2a41 Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Tue, 7 Nov 2023 16:25:15 +0000
Subject: [PATCH 15/16] Move implementation to
 src/string/memory_utils/x86_64/inline_memset.h and other minor changes

---
 libc/src/string/memory_utils/op_generic.h     |  43 ++----
 libc/src/string/memory_utils/utils.h          |   6 +
 .../memory_utils/x86_64/inline_memcpy.h       |   5 -
 .../memory_utils/x86_64/inline_memset.h       | 131 ++++++++++--------
 4 files changed, 92 insertions(+), 93 deletions(-)

diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index 2844501a7459044..2ee1a650ba71879 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -48,13 +48,6 @@ using generic_v256 = uint8_t __attribute__((__vector_size__(32)));
 using generic_v512 = uint8_t __attribute__((__vector_size__(64)));
 } // namespace LIBC_NAMESPACE
 
-namespace LIBC_NAMESPACE::sw_prefetch {
-// Size of a cacheline for software prefetching
-static constexpr size_t kCachelineSize = 64;
-// prefetch for write
-static inline void PrefetchW(CPtr dst) { __builtin_prefetch(dst, 1, 3); }
-} // namespace LIBC_NAMESPACE::sw_prefetch
-
 namespace LIBC_NAMESPACE::generic {
 
 // We accept three types of values as elements for generic operations:
@@ -141,19 +134,23 @@ template <typename T> struct Memset {
   static_assert(is_element_type_v<T>);
   static constexpr size_t SIZE = sizeof(T);
 
-  LIBC_INLINE static void block(Ptr dst, uint8_t value) {
+  LIBC_INLINE static void block_offset(Ptr dst, uint8_t value, size_t offset) {
     if constexpr (is_scalar_v<T> || is_vector_v<T>) {
-      store<T>(dst, splat<T>(value));
+      store<T>(dst + offset, splat<T>(value));
     } else if constexpr (is_array_v<T>) {
       using value_type = typename T::value_type;
       const auto Splat = splat<value_type>(value);
       for (size_t I = 0; I < array_size_v<T>; ++I)
-        store<value_type>(dst + (I * sizeof(value_type)), Splat);
+        store<value_type>(dst + offset + (I * sizeof(value_type)), Splat);
     }
   }
 
+  LIBC_INLINE static void block(Ptr dst, uint8_t value) {
+    block_offset(dst, value, 0);
+  }
+
   LIBC_INLINE static void tail(Ptr dst, uint8_t value, size_t count) {
-    block(dst + count - SIZE, value);
+    block_offset(dst, value, count - SIZE);
   }
 
   LIBC_INLINE static void head_tail(Ptr dst, uint8_t value, size_t count) {
@@ -161,33 +158,19 @@ template <typename T> struct Memset {
     tail(dst, value, count);
   }
 
-  LIBC_INLINE static void loop_and_tail(Ptr dst, uint8_t value, size_t count) {
+  LIBC_INLINE static void loop_and_tail_offset(Ptr dst, uint8_t value, size_t count, size_t offset) {
     static_assert(SIZE > 1, "a loop of size 1 does not need tail");
-    size_t offset = 0;
     do {
-      block(dst + offset, value);
+      block_offset(dst, value, offset);
       offset += SIZE;
     } while (offset < count - SIZE);
     tail(dst, value, count);
   }
 
-  template <size_t prefetch_distance, size_t prefetch_degree>
-  LIBC_INLINE static void loop_and_tail_prefetch(Ptr dst, uint8_t value,
-                                                 size_t count) {
-    size_t offset = 96;
-    while (offset + prefetch_degree + SIZE <= count) {
-      for (size_t i = 0; i < prefetch_degree / sw_prefetch::kCachelineSize; ++i)
-        sw_prefetch::PrefetchW(dst + offset + prefetch_distance +
-                               sw_prefetch::kCachelineSize * i);
-      for (size_t i = 0; i < prefetch_degree; i += SIZE, offset += SIZE)
-        block(dst + offset, value);
-    }
-    while (offset + SIZE < count) {
-      block(dst + offset, value);
-      offset += SIZE;
+    LIBC_INLINE static void loop_and_tail(Ptr dst, uint8_t value, size_t count) {
+      return loop_and_tail_offset(dst, value, count, 0);
     }
-    tail(dst, value, count);
-  }
+
 };
 
 template <typename T, typename... TS> struct MemsetSequence {
diff --git a/libc/src/string/memory_utils/utils.h b/libc/src/string/memory_utils/utils.h
index 85677e51fad0e09..62b3b7a0d728bd5 100644
--- a/libc/src/string/memory_utils/utils.h
+++ b/libc/src/string/memory_utils/utils.h
@@ -374,6 +374,12 @@ template <size_t SIZE> struct AlignHelper {
   uintptr_t offset_;
 };
 
+LIBC_INLINE void prefetch_for_write(CPtr dst) { __builtin_prefetch(dst, 1, 3); }
+
+LIBC_INLINE void prefetch_to_local_cache(CPtr dst) {
+  __builtin_prefetch(dst, 0, 3);
+}
+
 } // namespace LIBC_NAMESPACE
 
 #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_UTILS_H
diff --git a/libc/src/string/memory_utils/x86_64/inline_memcpy.h b/libc/src/string/memory_utils/x86_64/inline_memcpy.h
index f43230ffd8ad125..f851bcec09650d3 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memcpy.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memcpy.h
@@ -47,11 +47,6 @@ LIBC_INLINE_VAR constexpr size_t kRepMovsbThreshold =
 
 } // namespace x86
 
-// TODO: Move to a shared header when appropriate.
-[[maybe_unused]] LIBC_INLINE void prefetch_to_local_cache(const void *addr) {
-  __builtin_prefetch(addr, 0, 3);
-}
-
 [[maybe_unused]] LIBC_INLINE void
 inline_memcpy_x86_sse2_ge64(Ptr __restrict dst, CPtr __restrict src,
                             size_t count) {
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index e4eadf614adc6bf..2f132b45789b5c9 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -12,83 +12,98 @@
 #include "src/string/memory_utils/op_generic.h"
 #include "src/string/memory_utils/op_x86.h"
 #include "src/string/memory_utils/utils.h" // Ptr, CPtr
+#include "third_party/llvm/llvm-project/libc/src/string/memory_utils/inline_memcpy.h"
 
 #include <stddef.h> // size_t
 
 namespace LIBC_NAMESPACE {
 namespace x86 {
+// Size of one cache line for software prefetching
+LIBC_INLINE_VAR constexpr size_t kOneCachelineSize = 64;
+LIBC_INLINE_VAR constexpr size_t kTwoCachelinesSize = kOneCachelineSize * 2;
+LIBC_INLINE_VAR constexpr size_t kFiveCachelinesSize = kOneCachelineSize * 5;
+
 LIBC_INLINE_VAR constexpr bool kUseSoftwarePrefetchingMemset =
     LLVM_LIBC_IS_DEFINED(LIBC_COPT_MEMSET_X86_USE_SOFTWARE_PREFETCHING);
 
 } // namespace x86
 
 #if defined(__AVX512F__)
-  using uint128_t = generic_v128;
-  using uint256_t = generic_v256;
-  using uint512_t = generic_v512;
+using uint128_t = generic_v128;
+using uint256_t = generic_v256;
+using uint512_t = generic_v512;
 #elif defined(__AVX__)
-  using uint128_t = generic_v128;
-  using uint256_t = generic_v256;
-  using uint512_t = cpp::array<generic_v256, 2>;
+using uint128_t = generic_v128;
+using uint256_t = generic_v256;
+using uint512_t = cpp::array<generic_v256, 2>;
 #elif defined(__SSE2__)
-  using uint128_t = generic_v128;
-  using uint256_t = cpp::array<generic_v128, 2>;
-  using uint512_t = cpp::array<generic_v128, 4>;
+using uint128_t = generic_v128;
+using uint256_t = cpp::array<generic_v128, 2>;
+using uint512_t = cpp::array<generic_v128, 4>;
 #else
-  using uint128_t = cpp::array<uint64_t, 2>;
-  using uint256_t = cpp::array<uint64_t, 4>;
-  using uint512_t = cpp::array<uint64_t, 8>;
+using uint128_t = cpp::array<uint64_t, 2>;
+using uint256_t = cpp::array<uint64_t, 4>;
+using uint512_t = cpp::array<uint64_t, 8>;
 #endif
 
-  [[maybe_unused]] LIBC_INLINE static void
-  inline_memset_x86_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
-    // Prefetch one cacheline
-    sw_prefetch::PrefetchW(dst + sw_prefetch::kCachelineSize);
-    if (count <= 128)
-      return generic::Memset<uint512_t>::head_tail(dst, value, count);
-    // Prefetch the second cacheline
-    sw_prefetch::PrefetchW(dst + sw_prefetch::kCachelineSize * 2);
-    // Aligned loop
-    generic::Memset<uint256_t>::block(dst, value);
-    align_to_next_boundary<32>(dst, count);
-    if (count <= 192) {
-      return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
-    } else {
-      generic::Memset<uint512_t>::block(dst, value);
-      generic::Memset<uint256_t>::block(dst + sizeof(uint512_t), value);
-      return generic::Memset<uint256_t>::loop_and_tail_prefetch<320, 128>(
-          dst, value, count);
+[[maybe_unused]] LIBC_INLINE static void
+inline_memset_x86_gt64_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
+  size_t prefetch_distance = x86::kFiveCachelinesSize;
+  size_t prefetch_degree = x86::kTwoCachelinesSize;
+  size_t SIZE = sizeof(uint256_t);
+  // Prefetch one cache line
+  prefetch_for_write(dst + x86::kOneCachelineSize);
+  if (count <= 128)
+    return generic::Memset<uint512_t>::head_tail(dst, value, count);
+  // Prefetch the second cache line
+  prefetch_for_write(dst + x86::kTwoCachelinesSize);
+  // Aligned loop
+  generic::Memset<uint256_t>::block(dst, value);
+  align_to_next_boundary<32>(dst, count);
+  if (count <= 192) {
+    return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
+  } else {
+    generic::Memset<uint512_t>::block(dst, value);
+    generic::Memset<uint256_t>::block_offset(dst, value, SIZE);
+    size_t offset = 96;
+    while (offset + prefetch_degree + SIZE <= count) {
+      for (size_t i = 0; i < prefetch_degree / x86::kOneCachelineSize; ++i)
+        prefetch_for_write(dst + offset + prefetch_distance +
+                               x86::kOneCachelineSize * i);
+      for (size_t i = 0; i < prefetch_degree; i += SIZE, offset += SIZE)
+        generic::Memset<uint256_t>::block_offset(dst, value, offset);
     }
+    generic::Memset<uint256_t>::loop_and_tail_offset(dst, value, count, offset);
   }
+}
 
-  [[maybe_unused]] LIBC_INLINE static void
-  inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
-    if (count == 0)
-      return;
-    if (count == 1)
-      return generic::Memset<uint8_t>::block(dst, value);
-    if (count == 2)
-      return generic::Memset<uint16_t>::block(dst, value);
-    if (count == 3)
-      return generic::MemsetSequence<uint16_t, uint8_t>::block(dst, value);
-    if (count <= 8)
-      return generic::Memset<uint32_t>::head_tail(dst, value, count);
-    if (count <= 16)
-      return generic::Memset<uint64_t>::head_tail(dst, value, count);
-    if (count <= 32)
-      return generic::Memset<uint128_t>::head_tail(dst, value, count);
-    if (count <= 64)
-      return generic::Memset<uint256_t>::head_tail(dst, value, count);
-    if constexpr (x86::kUseSoftwarePrefetchingMemset) {
-      return inline_memset_x86_sw_prefetching(dst, value, count);
-    }
-    if (count <= 128)
-      return generic::Memset<uint512_t>::head_tail(dst, value, count);
-    // Aligned loop
-    generic::Memset<uint256_t>::block(dst, value);
-    align_to_next_boundary<32>(dst, count);
-    return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
-  }
+[[maybe_unused]] LIBC_INLINE static void
+inline_memset_x86(Ptr dst, uint8_t value, size_t count) {
+  if (count == 0)
+    return;
+  if (count == 1)
+    return generic::Memset<uint8_t>::block(dst, value);
+  if (count == 2)
+    return generic::Memset<uint16_t>::block(dst, value);
+  if (count == 3)
+    return generic::MemsetSequence<uint16_t, uint8_t>::block(dst, value);
+  if (count <= 8)
+    return generic::Memset<uint32_t>::head_tail(dst, value, count);
+  if (count <= 16)
+    return generic::Memset<uint64_t>::head_tail(dst, value, count);
+  if (count <= 32)
+    return generic::Memset<uint128_t>::head_tail(dst, value, count);
+  if (count <= 64)
+    return generic::Memset<uint256_t>::head_tail(dst, value, count);
+  if constexpr (x86::kUseSoftwarePrefetchingMemset)
+    return inline_memset_x86_gt64_sw_prefetching(dst, value, count);
+  if (count <= 128)
+    return generic::Memset<uint512_t>::head_tail(dst, value, count);
+  // Aligned loop
+  generic::Memset<uint256_t>::block(dst, value);
+  align_to_next_boundary<32>(dst, count);
+  return generic::Memset<uint256_t>::loop_and_tail(dst, value, count);
+}
 } // namespace LIBC_NAMESPACE
 
 #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_X86_64_INLINE_MEMSET_H

>From e86bcb7440c6a157907169dcc6fe25f0b322ef89 Mon Sep 17 00:00:00 2001
From: Your Name <milidoshi at google.com>
Date: Tue, 7 Nov 2023 16:27:51 +0000
Subject: [PATCH 16/16] Fix formatting

---
 libc/src/string/memory_utils/op_generic.h           | 10 +++++-----
 libc/src/string/memory_utils/x86_64/inline_memset.h |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index 2ee1a650ba71879..b508aca6e846bb4 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -158,7 +158,8 @@ template <typename T> struct Memset {
     tail(dst, value, count);
   }
 
-  LIBC_INLINE static void loop_and_tail_offset(Ptr dst, uint8_t value, size_t count, size_t offset) {
+  LIBC_INLINE static void loop_and_tail_offset(Ptr dst, uint8_t value,
+                                               size_t count, size_t offset) {
     static_assert(SIZE > 1, "a loop of size 1 does not need tail");
     do {
       block_offset(dst, value, offset);
@@ -167,10 +168,9 @@ template <typename T> struct Memset {
     tail(dst, value, count);
   }
 
-    LIBC_INLINE static void loop_and_tail(Ptr dst, uint8_t value, size_t count) {
-      return loop_and_tail_offset(dst, value, count, 0);
-    }
-
+  LIBC_INLINE static void loop_and_tail(Ptr dst, uint8_t value, size_t count) {
+    return loop_and_tail_offset(dst, value, count, 0);
+  }
 };
 
 template <typename T, typename... TS> struct MemsetSequence {
diff --git a/libc/src/string/memory_utils/x86_64/inline_memset.h b/libc/src/string/memory_utils/x86_64/inline_memset.h
index 2f132b45789b5c9..b745b8a6b7b1bcb 100644
--- a/libc/src/string/memory_utils/x86_64/inline_memset.h
+++ b/libc/src/string/memory_utils/x86_64/inline_memset.h
@@ -69,7 +69,7 @@ inline_memset_x86_gt64_sw_prefetching(Ptr dst, uint8_t value, size_t count) {
     while (offset + prefetch_degree + SIZE <= count) {
       for (size_t i = 0; i < prefetch_degree / x86::kOneCachelineSize; ++i)
         prefetch_for_write(dst + offset + prefetch_distance +
-                               x86::kOneCachelineSize * i);
+                           x86::kOneCachelineSize * i);
       for (size_t i = 0; i < prefetch_degree; i += SIZE, offset += SIZE)
         generic::Memset<uint256_t>::block_offset(dst, value, offset);
     }



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