[libc] [llvm] [libc] Some MSVC compatibility changes for src/string/memory_utils. (PR #158393)

via llvm-commits llvm-commits at lists.llvm.org
Fri Sep 12 18:14:21 PDT 2025 

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: None (lntue)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/158393.diff


9 Files Affected:

- (modified) libc/src/__support/endian_internal.h (+7-5) 
- (modified) libc/src/__support/macros/config.h (+2) 
- (modified) libc/src/string/memory_utils/CMakeLists.txt (+1) 
- (modified) libc/src/string/memory_utils/op_generic.h (+11) 
- (modified) libc/src/string/memory_utils/op_x86.h (+10) 
- (modified) libc/src/string/memory_utils/utils.h (+5) 
- (modified) libc/test/UnitTest/CMakeLists.txt (+1) 
- (modified) libc/test/UnitTest/LibcTest.h (+5) 
- (modified) utils/bazel/llvm-project-overlay/libc/test/UnitTest/BUILD.bazel (+1) 


``````````diff
diff --git a/libc/src/__support/endian_internal.h b/libc/src/__support/endian_internal.h
index 4ac8709625d3a..07cde7b905c4d 100644
--- a/libc/src/__support/endian_internal.h
+++ b/libc/src/__support/endian_internal.h
@@ -35,7 +35,7 @@ template <> LIBC_INLINE uint16_t byte_swap<uint16_t>(uint16_t value) {
 #if __has_builtin(__builtin_bswap16)
   return __builtin_bswap16(value);
 #else
-  return (v << 8) | (v >> 8);
+  return (value << 8) | (value >> 8);
 #endif // __builtin_bswap16
 }
 
@@ -43,8 +43,9 @@ template <> LIBC_INLINE uint32_t byte_swap<uint32_t>(uint32_t value) {
 #if __has_builtin(__builtin_bswap32)
   return __builtin_bswap32(value);
 #else
-  return byte_swap<uint16_t>(static_cast<uint16>(v >> 16)) ||
-         (static_cast<uint32_t>(byte_swap<uint16_t>(static_cast<uint16_t>(v)))
+  return byte_swap<uint16_t>(static_cast<uint16_t>(value >> 16)) ||
+         (static_cast<uint32_t>(
+              byte_swap<uint16_t>(static_cast<uint16_t>(value)))
           << 16);
 #endif // __builtin_bswap64
 }
@@ -53,8 +54,9 @@ template <> LIBC_INLINE uint64_t byte_swap<uint64_t>(uint64_t value) {
 #if __has_builtin(__builtin_bswap64)
   return __builtin_bswap64(value);
 #else
-  return byte_swap<uint32_t>(static_cast<uint32>(v >> 32)) ||
-         (static_cast<uint64_t>(byte_swap<uint32_t>(static_cast<uint32_t>(v)))
+  return byte_swap<uint32_t>(static_cast<uint32_t>(value >> 32)) ||
+         (static_cast<uint64_t>(
+              byte_swap<uint32_t>(static_cast<uint32_t>(value)))
           << 32);
 #endif // __builtin_bswap64
 }
diff --git a/libc/src/__support/macros/config.h b/libc/src/__support/macros/config.h
index 501a816d49631..b06a890c9c13c 100644
--- a/libc/src/__support/macros/config.h
+++ b/libc/src/__support/macros/config.h
@@ -46,6 +46,8 @@
 #define __builtin_expect(value, expectation) (value)
 #define __builtin_unreachable() __assume(0)
 
+#define __builtin_prefetch(X, Y, Z)
+
 #endif // LIBC_COMPILER_IS_MSVC
 
 #ifdef __clang__
diff --git a/libc/src/string/memory_utils/CMakeLists.txt b/libc/src/string/memory_utils/CMakeLists.txt
index 670db30129572..9cabfb9318012 100644
--- a/libc/src/string/memory_utils/CMakeLists.txt
+++ b/libc/src/string/memory_utils/CMakeLists.txt
@@ -42,6 +42,7 @@ add_header_library(
     libc.src.__support.macros.config
     libc.src.__support.macros.optimization
     libc.src.__support.macros.properties.architectures
+    libc.src.__support.macros.properties.compiler
 )
 
 add_header_library(
diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index 37603410e3a51..010f2187a4ffd 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -31,6 +31,7 @@
 #include "src/__support/macros/attributes.h" // LIBC_INLINE
 #include "src/__support/macros/config.h"     // LIBC_NAMESPACE_DECL
 #include "src/__support/macros/optimization.h"
+#include "src/__support/macros/properties/compiler.h"
 #include "src/__support/macros/properties/types.h" // LIBC_TYPES_HAS_INT64
 #include "src/string/memory_utils/op_builtin.h"
 #include "src/string/memory_utils/utils.h"
@@ -39,12 +40,22 @@ static_assert((UINTPTR_MAX == 4294967295U) ||
                   (UINTPTR_MAX == 18446744073709551615UL),
               "We currently only support 32- or 64-bit platforms");
 
+#ifdef LIBC_COMPILER_IS_MSVC
+
+namespace LIBC_NAMESPACE_DECL {
+using generic_v128 = __m128i;
+using generic_v256 = __m256i;
+using generic_v512 = __m512i;
+} // namespace LIBC_NAMESPACE_DECL
+
+#else
 namespace LIBC_NAMESPACE_DECL {
 // Compiler types using the vector attributes.
 using generic_v128 = uint8_t __attribute__((__vector_size__(16)));
 using generic_v256 = uint8_t __attribute__((__vector_size__(32)));
 using generic_v512 = uint8_t __attribute__((__vector_size__(64)));
 } // namespace LIBC_NAMESPACE_DECL
+#endif // LIBC_COMPILER_IS_MSVC
 
 namespace LIBC_NAMESPACE_DECL {
 namespace generic {
diff --git a/libc/src/string/memory_utils/op_x86.h b/libc/src/string/memory_utils/op_x86.h
index 8bd84120c4ffa..1b4052747552d 100644
--- a/libc/src/string/memory_utils/op_x86.h
+++ b/libc/src/string/memory_utils/op_x86.h
@@ -15,6 +15,7 @@
 #include "src/__support/macros/attributes.h" // LIBC_INLINE
 #include "src/__support/macros/config.h"     // LIBC_NAMESPACE_DECL
 #include "src/__support/macros/properties/architectures.h"
+#include "src/__support/macros/properties/compiler.h"
 
 #if defined(LIBC_TARGET_ARCH_IS_X86)
 
@@ -57,7 +58,12 @@ LIBC_INLINE_VAR constexpr bool K_AVX512_BW = LLVM_LIBC_IS_DEFINED(__AVX512BW__);
 // Memcpy repmovsb implementation
 struct Memcpy {
   LIBC_INLINE static void repmovsb(void *dst, const void *src, size_t count) {
+#ifdef LIBC_COMPILER_IS_MSVC
+    __movsb(static_cast<unsigned char *>(dst),
+            static_cast<const unsigned char *>(src), count);
+#else
     asm volatile("rep movsb" : "+D"(dst), "+S"(src), "+c"(count) : : "memory");
+#endif // LIBC_COMPILER_IS_MSVC
   }
 };
 
@@ -138,8 +144,10 @@ LIBC_INLINE MemcmpReturnType cmp_neq<uint64_t>(CPtr p1, CPtr p2,
 // When we use these SIMD types in template specialization GCC complains:
 // "ignoring attributes on template argument ‘__m128i’ [-Wignored-attributes]"
 // Therefore, we disable this warning in this file.
+#ifndef LIBC_COMPILER_IS_MSVC
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wignored-attributes"
+#endif // !LIBC_COMPILER_IS_MSVC
 
 ///////////////////////////////////////////////////////////////////////////////
 // Specializations for __m128i
@@ -366,7 +374,9 @@ LIBC_INLINE MemcmpReturnType cmp_neq<__m512i>(CPtr p1, CPtr p2, size_t offset) {
 }
 #endif // __AVX512BW__
 
+#ifndef LIBC_COMPILER_IS_MSVC
 #pragma GCC diagnostic pop
+#endif // !LIBC_COMPILER_IS_MSVC
 
 } // namespace generic
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/string/memory_utils/utils.h b/libc/src/string/memory_utils/utils.h
index 0f9c9e36a3dcd..86ff4f12e8c26 100644
--- a/libc/src/string/memory_utils/utils.h
+++ b/libc/src/string/memory_utils/utils.h
@@ -17,6 +17,7 @@
 #include "src/__support/macros/attributes.h" // LIBC_INLINE
 #include "src/__support/macros/config.h"     // LIBC_NAMESPACE_DECL
 #include "src/__support/macros/properties/architectures.h"
+#include "src/__support/macros/properties/compiler.h"
 
 #include <stddef.h> // size_t
 
@@ -90,13 +91,17 @@ LIBC_INLINE void memcpy_inline(void *__restrict dst,
   // different value of the Size parameter. This doesn't play well with GCC's
   // Value Range Analysis that wrongly detects out of bounds accesses. We
   // disable these warnings for the purpose of this function.
+#ifndef LIBC_COMPILER_IS_MSVC
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Warray-bounds"
 #pragma GCC diagnostic ignored "-Wstringop-overread"
 #pragma GCC diagnostic ignored "-Wstringop-overflow"
+#endif // !LIBC_COMPILER_IS_MSVC
   for (size_t i = 0; i < Size; ++i)
     static_cast<char *>(dst)[i] = static_cast<const char *>(src)[i];
+#ifndef LIBC_COMPILER_IS_MSVC
 #pragma GCC diagnostic pop
+#endif // !LIBC_COMPILER_IS_MSVC
 #endif
 }
 
diff --git a/libc/test/UnitTest/CMakeLists.txt b/libc/test/UnitTest/CMakeLists.txt
index f1a83fc601e5e..31d1e9dce8204 100644
--- a/libc/test/UnitTest/CMakeLists.txt
+++ b/libc/test/UnitTest/CMakeLists.txt
@@ -76,6 +76,7 @@ add_unittest_framework_library(
     libc.src.__support.CPP.string_view
     libc.src.__support.CPP.type_traits
     libc.src.__support.fixed_point.fx_rep
+    libc.src.__support.macros.properties.compiler
     libc.src.__support.macros.properties.types
     libc.src.__support.OSUtil.osutil
     libc.src.__support.uint128
diff --git a/libc/test/UnitTest/LibcTest.h b/libc/test/UnitTest/LibcTest.h
index fbeafd0bacb75..cf098cdd7a49a 100644
--- a/libc/test/UnitTest/LibcTest.h
+++ b/libc/test/UnitTest/LibcTest.h
@@ -30,6 +30,7 @@
 #include "src/__support/CPP/string_view.h"
 #include "src/__support/CPP/type_traits.h"
 #include "src/__support/c_string.h"
+#include "src/__support/macros/properties/compiler.h"
 #include "test/UnitTest/ExecuteFunction.h"
 #include "test/UnitTest/TestLogger.h"
 
@@ -260,7 +261,11 @@ constexpr char const *GetPrettyFunctionParamType(char const *str) {
 // This function recovers ParamType at compile time by using __PRETTY_FUNCTION__
 // It can be customized by using the REGISTER_TYPE_NAME macro below.
 template <typename ParamType> static constexpr const char *GetTypeName() {
+#ifdef LIBC_COMPILER_IS_MSVC
+  return GetPrettyFunctionParamType(__FUNCSIG__);
+#else
   return GetPrettyFunctionParamType(__PRETTY_FUNCTION__);
+#endif // LIBC_COMPILER_IS_MSVC
 }
 
 template <typename T>
diff --git a/utils/bazel/llvm-project-overlay/libc/test/UnitTest/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/test/UnitTest/BUILD.bazel
index 24baaf1983a08..318397615d0e3 100644
--- a/utils/bazel/llvm-project-overlay/libc/test/UnitTest/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/test/UnitTest/BUILD.bazel
@@ -62,6 +62,7 @@ libc_test_library(
         "//libc:__support_libc_errno",
         "//libc:__support_macros_config",
         "//libc:__support_macros_properties_architectures",
+        "//libc:__support_macros_properties_compiler",
         "//libc:__support_macros_properties_types",
         "//libc:__support_stringutil",
         "//libc:__support_uint128",

``````````

</details>


https://github.com/llvm/llvm-project/pull/158393

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