[libc][NFC] Split memcpy implementations per platform

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

Reviewed By: courbet

Differential Revision: https://reviews.llvm.org/D155099

4 files changed, 54 insertions, 28 deletions

diff --git a/libc/src/__support/CPP/string.h b/libc/src/__support/CPP/string.h
index fa73d53..a5611b9 100644
--- a/libc/src/__support/CPP/string.h
+++ b/libc/src/__support/CPP/string.h
@@ -56,7 +56,7 @@ public:
   }
   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)) {}
diff --git a/libc/src/string/memory_utils/CMakeLists.txt b/libc/src/string/memory_utils/CMakeLists.txt
index d6fa1d9..60a2482 100644
--- a/libc/src/string/memory_utils/CMakeLists.txt
+++ b/libc/src/string/memory_utils/CMakeLists.txt
@@ -18,6 +18,7 @@ add_header_library(
     op_generic.h
     op_x86.h
     riscv/bcmp_implementations.h
+    riscv/memcpy_implementations.h
     utils.h
     x86_64/bcmp_implementations.h
     x86_64/memcmp_implementations.h
diff --git a/libc/src/string/memory_utils/memcpy_implementations.h b/libc/src/string/memory_utils/memcpy_implementations.h
index a7bfc9e..657fbac 100644
--- a/libc/src/string/memory_utils/memcpy_implementations.h
+++ b/libc/src/string/memory_utils/memcpy_implementations.h
@@ -9,45 +9,37 @@
 #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
diff --git a/libc/src/string/memory_utils/riscv/memcpy_implementations.h b/libc/src/string/memory_utils/riscv/memcpy_implementations.h
new file mode 100644
index 0000000..a633f34
--- /dev/null
+++ b/libc/src/string/memory_utils/riscv/memcpy_implementations.h
@@ -0,0 +1,33 @@
+//===-- 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