[libc] Change __builtin_memcpy to inline_memcpy. #158345

lntue · 2025-09-12T18:44:39Z

No description provided.

llvmbot · 2025-09-12T18:45:18Z

@llvm/pr-subscribers-libc

Author: None (lntue)

Changes

Full diff: https://github.com/llvm/llvm-project/pull/158345.diff

15 Files Affected:

(modified) libc/src/__support/CMakeLists.txt (+1)
(modified) libc/src/__support/arg_list.h (+2-1)
(modified) libc/src/stdio/printf_core/CMakeLists.txt (+1)
(modified) libc/src/stdio/printf_core/float_dec_converter_limited.h (+3-2)
(modified) libc/src/stdlib/CMakeLists.txt (+1)
(modified) libc/src/stdlib/qsort_data.h (+6-5)
(modified) libc/src/string/CMakeLists.txt (+1)
(modified) libc/src/string/stpcpy.cpp (+2-1)
(modified) libc/src/string/string_utils.h (+2-1)
(modified) libc/src/wchar/CMakeLists.txt (+1)
(modified) libc/src/wchar/wcpcpy.cpp (+1-1)
(modified) libc/src/wchar/wcscpy.cpp (+1-1)
(modified) libc/src/wchar/wmemcpy.cpp (+2-1)
(modified) libc/src/wchar/wmempcpy.cpp (+2-1)
(modified) utils/bazel/llvm-project-overlay/libc/BUILD.bazel (+4)

diff --git a/libc/src/__support/CMakeLists.txt b/libc/src/__support/CMakeLists.txt
index b6e87ac336fb2..0ef09a9b8c9d0 100644
--- a/libc/src/__support/CMakeLists.txt
+++ b/libc/src/__support/CMakeLists.txt
@@ -302,6 +302,7 @@ add_header_library(
   DEPENDS
     libc.hdr.stdint_proxy
     libc.src.__support.common
+    libc.src.string.memory_utils.inline_memcpy
 )
 
 add_header_library(
diff --git a/libc/src/__support/arg_list.h b/libc/src/__support/arg_list.h
index 1e26a5e8ef9c7..7b78a9c0fe619 100644
--- a/libc/src/__support/arg_list.h
+++ b/libc/src/__support/arg_list.h
@@ -12,6 +12,7 @@
 #include "hdr/stdint_proxy.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
+#include "src/string/memory_utils/inline_memcpy.h"
 
 #include <stdarg.h>
 #include <stddef.h>
@@ -126,7 +127,7 @@ template <bool packed> class StructArgList {
 
     // Memcpy because pointer alignment may be illegal given a packed struct.
     T val;
-    __builtin_memcpy(&val, ptr, sizeof(T));
+    inline_memcpy(&val, ptr, sizeof(T));
 
     ptr =
         reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(ptr) + sizeof(T));
diff --git a/libc/src/stdio/printf_core/CMakeLists.txt b/libc/src/stdio/printf_core/CMakeLists.txt
index 76eb0a2fdaaa5..ee66145e60156 100644
--- a/libc/src/stdio/printf_core/CMakeLists.txt
+++ b/libc/src/stdio/printf_core/CMakeLists.txt
@@ -112,6 +112,7 @@ add_header_library(
     libc.src.__support.libc_assert
     libc.src.__support.uint128
     libc.src.__support.StringUtil.error_to_string
+    libc.src.string.memory_utils.inline_memcpy
 )
 
 add_header_library(
diff --git a/libc/src/stdio/printf_core/float_dec_converter_limited.h b/libc/src/stdio/printf_core/float_dec_converter_limited.h
index f468dbc8e2ae8..9cdc13573d320 100644
--- a/libc/src/stdio/printf_core/float_dec_converter_limited.h
+++ b/libc/src/stdio/printf_core/float_dec_converter_limited.h
@@ -53,6 +53,7 @@
 #include "src/stdio/printf_core/core_structs.h"
 #include "src/stdio/printf_core/float_inf_nan_converter.h"
 #include "src/stdio/printf_core/writer.h"
+#include "src/string/memory_utils/inline_memcpy.h"
 
 namespace LIBC_NAMESPACE_DECL {
 namespace printf_core {
@@ -250,7 +251,7 @@ DigitsOutput decimal_digits(DigitsInput input, int precision, bool e_mode) {
   // there's space for it in the DigitsOutput buffer).
   DigitsOutput output;
   output.ndigits = view.size();
-  __builtin_memcpy(output.digits, view.data(), output.ndigits);
+  inline_memcpy(output.digits, view.data(), output.ndigits);
 
   // Set up the output exponent, which is done differently depending on mode.
   // Also, figure out whether we have one digit too many, and if so, set the
@@ -551,7 +552,7 @@ convert_float_inner(Writer<write_mode> *writer, const FormatSection &to_conv,
     cpp::string_view expview = expcvt.view();
     expbuf[0] = internal::islower(to_conv.conv_name) ? 'e' : 'E';
     explen = expview.size() + 1;
-    __builtin_memcpy(expbuf + 1, expview.data(), expview.size());
+    inline_memcpy(expbuf + 1, expview.data(), expview.size());
   }
 
   // Now we know enough to work out the length of the unpadded output:
diff --git a/libc/src/stdlib/CMakeLists.txt b/libc/src/stdlib/CMakeLists.txt
index aa653c38a8c3f..c464f82dcbda7 100644
--- a/libc/src/stdlib/CMakeLists.txt
+++ b/libc/src/stdlib/CMakeLists.txt
@@ -292,6 +292,7 @@ add_header_library(
     libc.hdr.stdint_proxy
     libc.include.stdlib
     libc.src.__support.CPP.cstddef
+    libc.src.string.memory_utils.inline_memcpy    
 )
 
 add_entrypoint_object(
diff --git a/libc/src/stdlib/qsort_data.h b/libc/src/stdlib/qsort_data.h
index 739fce88ab75d..4f9774088fbd3 100644
--- a/libc/src/stdlib/qsort_data.h
+++ b/libc/src/stdlib/qsort_data.h
@@ -12,6 +12,7 @@
 #include "hdr/stdint_proxy.h"
 #include "src/__support/CPP/cstddef.h"
 #include "src/__support/macros/config.h"
+#include "src/string/memory_utils/inline_memcpy.h"
 
 namespace LIBC_NAMESPACE_DECL {
 namespace internal {
@@ -54,9 +55,9 @@ class ArrayGenericSize {
     const cpp::byte *elem_i_block_end = elem_i + (elem_size - elem_size_rem);
 
     while (elem_i != elem_i_block_end) {
-      __builtin_memcpy(tmp_block, elem_i, BLOCK_SIZE);
-      __builtin_memcpy(elem_i, elem_j, BLOCK_SIZE);
-      __builtin_memcpy(elem_j, tmp_block, BLOCK_SIZE);
+      inline_memcpy(tmp_block, elem_i, BLOCK_SIZE);
+      inline_memcpy(elem_i, elem_j, BLOCK_SIZE);
+      inline_memcpy(elem_j, tmp_block, BLOCK_SIZE);
 
       elem_i += BLOCK_SIZE;
       elem_j += BLOCK_SIZE;
@@ -112,9 +113,9 @@ template <size_t ELEM_SIZE> class ArrayFixedSize {
     cpp::byte *elem_i = get_internal(i);
     cpp::byte *elem_j = get_internal(j);
 
-    __builtin_memcpy(tmp, elem_i, ELEM_SIZE);
+    inline_memcpy(tmp, elem_i, ELEM_SIZE);
     __builtin_memmove(elem_i, elem_j, ELEM_SIZE);
-    __builtin_memcpy(elem_j, tmp, ELEM_SIZE);
+    inline_memcpy(elem_j, tmp, ELEM_SIZE);
   }
 
   LIBC_INLINE size_t len() const { return array_len; }
diff --git a/libc/src/string/CMakeLists.txt b/libc/src/string/CMakeLists.txt
index 5c9f622d44397..b8cdb2a7d3538 100644
--- a/libc/src/string/CMakeLists.txt
+++ b/libc/src/string/CMakeLists.txt
@@ -22,6 +22,7 @@ add_header_library(
     libc.src.__support.CPP.type_traits
     libc.src.__support.CPP.simd
     libc.src.__support.common
+    libc.src.string.memory_utils.inline_memcpy
   ${string_config_options}
 )
 
diff --git a/libc/src/string/stpcpy.cpp b/libc/src/string/stpcpy.cpp
index 48c0db950ace0..fefae81172585 100644
--- a/libc/src/string/stpcpy.cpp
+++ b/libc/src/string/stpcpy.cpp
@@ -8,6 +8,7 @@
 
 #include "src/string/stpcpy.h"
 #include "src/__support/macros/config.h"
+#include "src/string/memory_utils/inline_memcpy.h"
 #include "src/string/string_utils.h"
 
 #include "src/__support/common.h"
@@ -17,7 +18,7 @@ namespace LIBC_NAMESPACE_DECL {
 LLVM_LIBC_FUNCTION(char *, stpcpy,
                    (char *__restrict dest, const char *__restrict src)) {
   size_t size = internal::string_length(src) + 1;
-  __builtin_memcpy(dest, src, size);
+  inline_memcpy(dest, src, size);
   char *result = dest + size;
 
   if (result != nullptr)
diff --git a/libc/src/string/string_utils.h b/libc/src/string/string_utils.h
index 10803488b6cf5..9d636d02f4756 100644
--- a/libc/src/string/string_utils.h
+++ b/libc/src/string/string_utils.h
@@ -21,6 +21,7 @@
 #include "src/__support/CPP/type_traits.h" // cpp::is_same_v
 #include "src/__support/macros/config.h"
 #include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
+#include "src/string/memory_utils/inline_memcpy.h"
 
 #if defined(LIBC_COPT_STRING_UNSAFE_WIDE_READ)
 #if LIBC_HAS_VECTOR_TYPE
@@ -242,7 +243,7 @@ LIBC_INLINE size_t strlcpy(char *__restrict dst, const char *__restrict src,
   if (!size)
     return len;
   size_t n = len < size - 1 ? len : size - 1;
-  __builtin_memcpy(dst, src, n);
+  inline_memcpy(dst, src, n);
   dst[n] = '\0';
   return len;
 }
diff --git a/libc/src/wchar/CMakeLists.txt b/libc/src/wchar/CMakeLists.txt
index 9ba0a06c57b7f..adde382bf0950 100644
--- a/libc/src/wchar/CMakeLists.txt
+++ b/libc/src/wchar/CMakeLists.txt
@@ -452,6 +452,7 @@ add_entrypoint_object(
   DEPENDS
     libc.hdr.types.size_t
     libc.hdr.wchar_macros
+    libc.src.string.memory_utils.inline_memcpy
 )
 
 add_entrypoint_object(
diff --git a/libc/src/wchar/wcpcpy.cpp b/libc/src/wchar/wcpcpy.cpp
index 9e2b12f09eb05..b6d80d4d671d9 100644
--- a/libc/src/wchar/wcpcpy.cpp
+++ b/libc/src/wchar/wcpcpy.cpp
@@ -19,7 +19,7 @@ namespace LIBC_NAMESPACE_DECL {
 LLVM_LIBC_FUNCTION(wchar_t *, wcpcpy,
                    (wchar_t *__restrict s1, const wchar_t *__restrict s2)) {
   size_t size = internal::string_length(s2);
-  __builtin_memcpy(s1, s2, (size + 1) * sizeof(wchar_t));
+  inline_memcpy(s1, s2, (size + 1) * sizeof(wchar_t));
   wchar_t *result = s1 + size;
   return result;
 }
diff --git a/libc/src/wchar/wcscpy.cpp b/libc/src/wchar/wcscpy.cpp
index 01ba994cecbb2..703706e6a7be8 100644
--- a/libc/src/wchar/wcscpy.cpp
+++ b/libc/src/wchar/wcscpy.cpp
@@ -19,7 +19,7 @@ namespace LIBC_NAMESPACE_DECL {
 LLVM_LIBC_FUNCTION(wchar_t *, wcscpy,
                    (wchar_t *__restrict s1, const wchar_t *__restrict s2)) {
   size_t size = internal::string_length(s2) + 1;
-  __builtin_memcpy(s1, s2, size * sizeof(wchar_t));
+  inline_memcpy(s1, s2, size * sizeof(wchar_t));
   return s1;
 }
 
diff --git a/libc/src/wchar/wmemcpy.cpp b/libc/src/wchar/wmemcpy.cpp
index bf92309b20944..56708d6cee496 100644
--- a/libc/src/wchar/wmemcpy.cpp
+++ b/libc/src/wchar/wmemcpy.cpp
@@ -12,13 +12,14 @@
 #include "hdr/types/wchar_t.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
+#include "src/string/memory_utils/inline_memcpy.h"
 
 namespace LIBC_NAMESPACE_DECL {
 
 LLVM_LIBC_FUNCTION(wchar_t *, wmemcpy,
                    (wchar_t *__restrict s1, const wchar_t *__restrict s2,
                     size_t n)) {
-  __builtin_memcpy(s1, s2, n * sizeof(wchar_t));
+  inline_memcpy(s1, s2, n * sizeof(wchar_t));
   return s1;
 }
 
diff --git a/libc/src/wchar/wmempcpy.cpp b/libc/src/wchar/wmempcpy.cpp
index 21e16210a757a..d8b89c0a88d05 100644
--- a/libc/src/wchar/wmempcpy.cpp
+++ b/libc/src/wchar/wmempcpy.cpp
@@ -11,13 +11,14 @@
 #include "hdr/types/size_t.h"
 #include "hdr/types/wchar_t.h"
 #include "src/__support/common.h"
+#include "src/string/memory_utils/inline_memcpy.h"
 
 namespace LIBC_NAMESPACE_DECL {
 
 LLVM_LIBC_FUNCTION(wchar_t *, wmempcpy,
                    (wchar_t *__restrict to, const wchar_t *__restrict from,
                     size_t size)) {
-  __builtin_memcpy(to, from, size * sizeof(wchar_t));
+  inline_memcpy(to, from, size * sizeof(wchar_t));
   return reinterpret_cast<wchar_t *>(to) + size;
 }
 
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index d9b1bb5635aaf..a955f7f4916ac 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -818,6 +818,7 @@ libc_support_library(
     hdrs = ["src/__support/arg_list.h"],
     deps = [
         ":__support_common",
+        ":string_memory_utils",
     ],
 )
 
@@ -5003,6 +5004,7 @@ libc_support_library(
         ":__support_cpp_bit",
         ":__support_cpp_cstddef",
         ":__support_macros_attributes",
+        ":string_memory_utils",
     ],
 )
 
@@ -6945,6 +6947,7 @@ libc_function(
     deps = [
         ":__support_common",
         ":__support_macros_config",
+        ":string_memory_utils",
         ":types_size_t",
         ":types_wchar_t",
     ],
@@ -6968,6 +6971,7 @@ libc_function(
     hdrs = ["src/wchar/wmempcpy.h"],
     deps = [
         ":__support_common",
+        ":string_memory_utils",
         ":types_size_t",
         ":types_wchar_t",
     ],

michaelrj-google

LGTM.

For context the reason behind this change is MSVC doesn't support __builtin_memcpy so we're moving everything to inline_memcpy. We can discuss how to adjust this so it's more optimal later but this change is needed to unblock MSVC.

[libc] Change __builtin_memcpy to inline_memcpy.

3dd3f25

lntue requested review from jhuber6, michaelrj-google and vonosmas September 12, 2025 18:44

lntue requested review from aaronmondal, keith and rupprecht as code owners September 12, 2025 18:44

llvmbot added libc bazel "Peripheral" support tier build system: utils/bazel labels Sep 12, 2025

michaelrj-google approved these changes Sep 12, 2025

View reviewed changes

lntue merged commit f019e23 into llvm:main Sep 12, 2025
22 of 23 checks passed

lntue deleted the memcpy branch September 12, 2025 21:57

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[libc] Change __builtin_memcpy to inline_memcpy. #158345

[libc] Change __builtin_memcpy to inline_memcpy. #158345

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lntue commented Sep 12, 2025

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[libc] Change __builtin_memcpy to inline_memcpy. #158345

[libc] Change __builtin_memcpy to inline_memcpy. #158345

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lntue commented Sep 12, 2025

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