[libc][NFC] Split memcpy implementations per platform

[gchatelet]

Summary

This is a follow up on D154800 and D154770 to make the code structure more principled and avoid too many nested #ifdef/#endif.

[gchatelet]

• Remove unused includes
• Fix wrong signature

[gchatelet]

• Fix arguments

[gchatelet]

rebase

libc/src/__support/CPP/string.h

public:
   LIBC_INLINE constexpr string() {}
   LIBC_INLINE string(const string &other) { this->operator+=(other); }
   LIBC_INLINE constexpr string(string &&other)
       : buffer_(other.buffer_), size_(other.size_), capacity_(other.capacity_) {
     other.reset_no_deallocate();
   }
   LIBC_INLINE string(const char *cstr, size_t count) {
     resize(count);
-    inline_memcpy((void *)buffer_, (const void *)cstr, count);
+    inline_memcpy(buffer_, cstr, count);
   }
   LIBC_INLINE string(const char *cstr)
       : string(cstr, ::__llvm_libc::internal::string_length(cstr)) {}
   LIBC_INLINE string(size_t size_, char value) {
     resize(size_);
     inline_memset((void *)buffer_, value, size_);
   }
 

libc/src/string/memory_utils/CMakeLists.txt

-#TODO(michaelrj): split out the implementations from memory_utils
+# TODO(michaelrj): split out the implementations from memory_utils
 add_header_library(
   memory_utils
   HDRS
     aarch64/memcmp_implementations.h
     aarch64/memcpy_implementations.h
     bcmp_implementations.h
     bzero_implementations.h
     generic/aligned_access.h
     generic/byte_per_byte.h
     memcmp_implementations.h
     memcpy_implementations.h
     memmove_implementations.h
     memset_implementations.h
     op_aarch64.h
     op_builtin.h
     op_generic.h
     op_x86.h
+    riscv/memcpy_implementations.h
     utils.h
     x86_64/memcmp_implementations.h
     x86_64/memcpy_implementations.h
   DEPS
     libc.src.__support.common
     libc.src.__support.CPP.bit
     libc.src.__support.CPP.cstddef
     libc.src.__support.CPP.type_traits

libc/src/string/memory_utils/memcpy_implementations.h

 //===-- Memcpy implementation -----------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMCPY_IMPLEMENTATIONS_H
 #define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMCPY_IMPLEMENTATIONS_H
 
-#include "src/__support/macros/config.h"       // LIBC_INLINE
-#include "src/__support/macros/optimization.h" // LIBC_LOOP_NOUNROLL
-#include "src/__support/macros/properties/architectures.h"
-#include "src/string/memory_utils/generic/aligned_access.h"
-#include "src/string/memory_utils/generic/byte_per_byte.h"
-#include "src/string/memory_utils/op_builtin.h"
-#include "src/string/memory_utils/utils.h"
+#include "src/__support/macros/config.h"                   // LIBC_INLINE
+#include "src/__support/macros/properties/architectures.h" // LIBC_TARGET_ARCH_IS_
+#include "src/string/memory_utils/utils.h"                 // Ptr, CPtr
 
 #include <stddef.h> // size_t
 
-#if defined(LIBC_TARGET_ARCH_IS_X86)
+#if defined(LIBC_COPT_MEMCPY_USE_EMBEDDED_TINY)
+#include "src/string/memory_utils/generic/byte_per_byte.h"
+#define LIBC_SRC_STRING_MEMORY_UTILS_MEMCPY inline_memcpy_byte_per_byte
+#elif defined(LIBC_TARGET_ARCH_IS_X86)
 #include "src/string/memory_utils/x86_64/memcpy_implementations.h"
+#define LIBC_SRC_STRING_MEMORY_UTILS_MEMCPY                                    \
+  inline_memcpy_x86_maybe_interpose_repmovsb
 #elif defined(LIBC_TARGET_ARCH_IS_AARCH64)
 #include "src/string/memory_utils/aarch64/memcpy_implementations.h"
+#define LIBC_SRC_STRING_MEMORY_UTILS_MEMCPY inline_memcpy_aarch64
+#elif defined(LIBC_TARGET_ARCH_IS_ANY_RISCV)
+#include "src/string/memory_utils/riscv/memcpy_implementations.h"
+#define LIBC_SRC_STRING_MEMORY_UTILS_MEMCPY inline_memcpy_riscv
+#else
+// We may want to error instead of defaulting to suboptimal implementation.
+#include "src/string/memory_utils/generic/byte_per_byte.h"
+#define LIBC_SRC_STRING_MEMORY_UTILS_MEMCPY inline_memcpy_byte_per_byte
 #endif
 
 namespace __llvm_libc {
 
-LIBC_INLINE void inline_memcpy(Ptr __restrict dst, CPtr __restrict src,
-                               size_t count) {
-  using namespace __llvm_libc::builtin;
-#if defined(LIBC_COPT_MEMCPY_USE_EMBEDDED_TINY)
-  return inline_memcpy_byte_per_byte(dst, src, count);
-#elif defined(LIBC_TARGET_ARCH_IS_X86)
-  return inline_memcpy_x86_maybe_interpose_repmovsb(dst, src, count);
-#elif defined(LIBC_TARGET_ARCH_IS_AARCH64)
-  return inline_memcpy_aarch64(dst, src, count);
-#elif defined(LIBC_TARGET_ARCH_IS_RISCV64)
-  return inline_memcpy_aligned_access_64bit(dst, src, count);
-#elif defined(LIBC_TARGET_ARCH_IS_RISCV32)
-  return inline_memcpy_aligned_access_32bit(dst, src, count);
-#else
-  return inline_memcpy_byte_per_byte(dst, src, count);
-#endif
-}
-
 LIBC_INLINE void inline_memcpy(void *__restrict dst, const void *__restrict src,
                                size_t count) {
-  inline_memcpy(reinterpret_cast<Ptr>(dst), reinterpret_cast<CPtr>(src), count);
+  LIBC_SRC_STRING_MEMORY_UTILS_MEMCPY(reinterpret_cast<Ptr>(dst),
+                                      reinterpret_cast<CPtr>(src), count);
 }
 
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMCPY_IMPLEMENTATIONS_H

libc/src/string/memory_utils/riscv/memcpy_implementations.h

+//===-- Memcpy implementation for riscv -------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+#ifndef LIBC_SRC_STRING_MEMORY_UTILS_RISCV_MEMCPY_IMPLEMENTATIONS_H
+#define LIBC_SRC_STRING_MEMORY_UTILS_RISCV_MEMCPY_IMPLEMENTATIONS_H
+
+#include "src/__support/macros/attributes.h"               // LIBC_INLINE
+#include "src/__support/macros/properties/architectures.h" // LIBC_TARGET_ARCH_IS_RISCV64
+#include "src/string/memory_utils/generic/aligned_access.h"
+#include "src/string/memory_utils/utils.h" // Ptr, CPtr
+
+#include <stddef.h> // size_t
+
+namespace __llvm_libc {
+
+[[maybe_unused]] LIBC_INLINE void
+inline_memcpy_riscv(Ptr __restrict dst, CPtr __restrict src, size_t count) {
+#if defined(LIBC_TARGET_ARCH_IS_RISCV64)
+  return inline_memcpy_aligned_access_64bit(dst, src, count);
+#elif defined(LIBC_TARGET_ARCH_IS_RISCV32)
+  return inline_memcpy_aligned_access_32bit(dst, src, count);
+#else
+#error "Unimplemented"
+#endif
+}
+
+} // namespace __llvm_libc
+
+#endif // LIBC_SRC_STRING_MEMORY_UTILS_RISCV_MEMCPY_IMPLEMENTATIONS_H

utils/bazel/llvm-project-overlay/libc/BUILD.bazel

textual_hdrs = [
         "src/string/memory_utils/bzero_implementations.h",
         "src/string/memory_utils/generic/aligned_access.h",
         "src/string/memory_utils/generic/byte_per_byte.h",
         "src/string/memory_utils/memcmp_implementations.h",
         "src/string/memory_utils/memcpy_implementations.h",
         "src/string/memory_utils/memmem_implementations.h",
         "src/string/memory_utils/memmove_implementations.h",
         "src/string/memory_utils/memset_implementations.h",
+        "src/string/memory_utils/riscv/memcpy_implementations.h",
         "src/string/memory_utils/strcmp_implementations.h",
         "src/string/memory_utils/strstr_implementations.h",
         "src/string/memory_utils/x86_64/memcmp_implementations.h",
         "src/string/memory_utils/x86_64/memcpy_implementations.h",
     ],
     deps = [
         ":__support_common",
         ":__support_cpp_array",