fix ci

.buildkite/ci.mjs

@@ -470,19 +470,30 @@ function getBuildCommand(target, options, label) {
  */
 function getWindowsArm64CrossFlags(target) {
   if (target.os === "windows" && target.arch === "aarch64") {
-    return " --toolchain windows-aarch64 -DSKIP_CODEGEN=ON -DCMAKE_C_COMPILER=clang-cl -DCMAKE_CXX_COMPILER=clang-cl";
+    return " --toolchain windows-aarch64";
   }
   return "";
 }
 
+
 /**
  * @param {Platform} platform
  * @param {PipelineOptions} options
  * @returns {Step}
  */
 function getBuildCppStep(platform, options) {
+  const { os, arch } = platform;
   const command = getBuildCommand(platform, options);
   const crossFlags = getWindowsArm64CrossFlags(platform);
+
+  // Build commands for C++ dependencies and bun
+  const buildCommands = [`${command}${crossFlags} --target bun`, `${command}${crossFlags} --target dependencies`];
+
+  // Cross-compiling Windows ARM64 from x64 requires Rust ARM64 target
+  if (os === "windows" && arch === "aarch64") {
+    buildCommands.unshift("rustup target add aarch64-pc-windows-msvc");
+  }
+
   return {
     key: `${getTargetKey(platform)}-build-cpp`,
     label: `${getTargetLabel(platform)} - build-cpp`,
@@ -496,7 +507,7 @@ function getBuildCppStep(platform, options) {
     // We used to build the C++ dependencies and bun in separate steps.
     // However, as long as the zig build takes longer than both sequentially,
     // it's cheaper to run them in the same step. Can be revisited in the future.
-    command: [`${command}${crossFlags} --target bun`, `${command}${crossFlags} --target dependencies`],
+    command: buildCommands,
   };
 }
 

cmake/targets/BuildBoringSSL.cmake

@@ -7,6 +7,13 @@ register_repository(
     4f4f5ef8ebc6e23cbf393428f0ab1b526773f7ac
 )
 
+set(BORINGSSL_CMAKE_ARGS -DBUILD_SHARED_LIBS=OFF)
+
+# Disable ASM on Windows ARM64 to avoid mixing non-ARM object files into ARM64 libs
+if(WIN32 AND CMAKE_SYSTEM_PROCESSOR MATCHES "ARM64|aarch64|AARCH64")
+  list(APPEND BORINGSSL_CMAKE_ARGS -DOPENSSL_NO_ASM=1)
+endif()
+
 register_cmake_command(
   TARGET
     boringssl
@@ -15,7 +22,7 @@ register_cmake_command(
     ssl
     decrepit
   ARGS
-    -DBUILD_SHARED_LIBS=OFF
+    ${BORINGSSL_CMAKE_ARGS}
   INCLUDES
     include
 )

cmake/targets/BuildBun.cmake

@@ -1457,6 +1457,8 @@ if(NOT BUN_CPP_ONLY)
   # ==856230==See https://github.com/google/sanitizers/issues/856 for possible workarounds.
   # the linked issue refers to very old kernels but this still happens to us on modern ones.
   # disabling ASLR to run the binary works around it
+  # Skip post-build test/features when cross-compiling (can't run the target binary on the host)
+  if(NOT CMAKE_CROSSCOMPILING)
   set(TEST_BUN_COMMAND_BASE ${BUILD_PATH}/${bunExe} --revision)
   set(TEST_BUN_COMMAND_ENV_WRAP
     ${CMAKE_COMMAND} -E env BUN_DEBUG_QUIET_LOGS=1)
@@ -1505,6 +1507,7 @@ if(NOT BUN_CPP_ONLY)
         ${BUILD_PATH}/features.json
     )
   endif()
+  endif() # NOT CMAKE_CROSSCOMPILING
 
   if(CMAKE_HOST_APPLE AND bunStrip)
     register_command(
@@ -1551,7 +1554,10 @@ if(NOT BUN_CPP_ONLY)
       string(REPLACE bun ${bunTriplet} bunPath ${bun})
     endif()
 
-    set(bunFiles ${bunExe} features.json)
+    set(bunFiles ${bunExe})
+    if(NOT CMAKE_CROSSCOMPILING)
+      list(APPEND bunFiles features.json)
+    endif()
     if(WIN32)
       list(APPEND bunFiles ${bun}.pdb)
     elseif(APPLE)

cmake/targets/BuildLibArchive.cmake

@@ -41,6 +41,7 @@ register_cmake_command(
     # spawn a processes to compress instead of using the library.
     -DENABLE_ZLIB=OFF
     -DHAVE_ZLIB_H=ON
+    -DENABLE_CNG=OFF
     -DCMAKE_C_FLAGS="-I${VENDOR_PATH}/zlib"
   LIB_PATH
     libarchive

cmake/targets/BuildLolHtml.cmake

@@ -26,6 +26,12 @@ if(RELEASE)
   list(APPEND LOLHTML_BUILD_ARGS --release)
 endif()
 
+# Cross-compilation: tell cargo to target ARM64
+if(WIN32 AND CMAKE_SYSTEM_PROCESSOR MATCHES "ARM64|aarch64|AARCH64")
+  list(APPEND LOLHTML_BUILD_ARGS --target aarch64-pc-windows-msvc)
+  set(LOLHTML_LIBRARY ${LOLHTML_BUILD_PATH}/aarch64-pc-windows-msvc/${LOLHTML_BUILD_TYPE}/${CMAKE_STATIC_LIBRARY_PREFIX}lolhtml${CMAKE_STATIC_LIBRARY_SUFFIX})
+endif()
+
 # Windows requires unwind tables, apparently.
 if (NOT WIN32)
   # The encoded escape sequences are intentional. They're how you delimit multiple arguments in a single environment variable.
@@ -51,7 +57,12 @@ if(WIN32)
   if(MSVC_VERSIONS)
     list(GET MSVC_VERSIONS -1 MSVC_LATEST)  # Get the latest version
     if(CMAKE_SYSTEM_PROCESSOR MATCHES "ARM64|aarch64")
-      set(MSVC_LINK_PATH "${MSVC_LATEST}/bin/HostARM64/arm64/link.exe")
+      # Use Hostx64/arm64 for cross-compilation from x64, fall back to native
+      if(EXISTS "${MSVC_LATEST}/bin/Hostx64/arm64/link.exe")
+        set(MSVC_LINK_PATH "${MSVC_LATEST}/bin/Hostx64/arm64/link.exe")
+      else()
+        set(MSVC_LINK_PATH "${MSVC_LATEST}/bin/HostARM64/arm64/link.exe")
+      endif()
       set(CARGO_LINKER_VAR "CARGO_TARGET_AARCH64_PC_WINDOWS_MSVC_LINKER")
     else()
       set(MSVC_LINK_PATH "${MSVC_LATEST}/bin/Hostx64/x64/link.exe")

cmake/toolchains/windows-aarch64.cmake

@@ -4,17 +4,35 @@ set(CMAKE_SYSTEM_PROCESSOR aarch64)
 set(CMAKE_C_COMPILER_WORKS ON)
 set(CMAKE_CXX_COMPILER_WORKS ON)
 
-# Force ARM64 architecture ID - this is what CMake uses to determine /machine: flag
-set(MSVC_C_ARCHITECTURE_ID ARM64 CACHE INTERNAL "")
-set(MSVC_CXX_ARCHITECTURE_ID ARM64 CACHE INTERNAL "")
+# Prevent CMake from trying to link ARM64 executables during try_compile tests.
+# The x64 host can't link ARM64 executables (missing ARM64 CRT/system libs).
+set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
 
-# CMake 4.0+ policy CMP0197 controls how MSVC machine type flags are handled
-set(CMAKE_POLICY_DEFAULT_CMP0197 NEW CACHE INTERNAL "")
+# The rest only applies when building on Windows (C++ and link steps).
+# The Zig step runs on Linux and only needs CMAKE_SYSTEM_NAME/PROCESSOR above.
+if(CMAKE_HOST_SYSTEM_NAME STREQUAL "Windows")
 
-# Clear any inherited static linker flags that might have wrong machine types
-set(CMAKE_STATIC_LINKER_FLAGS "" CACHE STRING "" FORCE)
+  # Set compiler target for ARM64 cross-compilation
+  set(CMAKE_C_COMPILER_TARGET aarch64-pc-windows-msvc CACHE STRING "" FORCE)
+  set(CMAKE_CXX_COMPILER_TARGET aarch64-pc-windows-msvc CACHE STRING "" FORCE)
 
-# Use wrapper script for llvm-lib that strips /machine:x64 flags
-# This works around CMake 4.1.0 bug where both ARM64 and x64 machine flags are added
-get_filename_component(_TOOLCHAIN_DIR "${CMAKE_CURRENT_LIST_DIR}" DIRECTORY)
-set(CMAKE_AR "${_TOOLCHAIN_DIR}/scripts/llvm-lib-wrapper.bat" CACHE FILEPATH "" FORCE)
+  # ARM64 has lock-free atomics (highway's FindAtomics check can't run ARM64 test binary on x64)
+  set(ATOMICS_LOCK_FREE_INSTRUCTIONS TRUE CACHE BOOL "" FORCE)
+  set(HAVE_CXX_ATOMICS_WITHOUT_LIB TRUE CACHE BOOL "" FORCE)
+  set(HAVE_CXX_ATOMICS64_WITHOUT_LIB TRUE CACHE BOOL "" FORCE)
+
+  # Force ARM64 architecture ID - this is what CMake uses to determine /machine: flag
+  set(MSVC_C_ARCHITECTURE_ID ARM64 CACHE INTERNAL "")
+  set(MSVC_CXX_ARCHITECTURE_ID ARM64 CACHE INTERNAL "")
+
+  # CMake 4.0+ policy CMP0197 controls how MSVC machine type flags are handled
+  set(CMAKE_POLICY_DEFAULT_CMP0197 NEW CACHE INTERNAL "")
+
+  # Clear any inherited static linker flags that might have wrong machine types
+  set(CMAKE_STATIC_LINKER_FLAGS "" CACHE STRING "" FORCE)
+
+  # Use wrapper script for llvm-lib that strips /machine:x64 flags
+  # This works around CMake 4.1.0 bug where both ARM64 and x64 machine flags are added
+  get_filename_component(_TOOLCHAIN_DIR "${CMAKE_CURRENT_LIST_DIR}" DIRECTORY)
+  set(CMAKE_AR "${_TOOLCHAIN_DIR}/scripts/llvm-lib-wrapper.bat" CACHE FILEPATH "" FORCE)
+endif()

cmake/tools/SetupWebKit.cmake

@@ -259,3 +259,19 @@ file(RENAME ${CACHE_PATH}/bun-webkit ${WEBKIT_PATH})
 if(APPLE)
   file(REMOVE_RECURSE ${WEBKIT_INCLUDE_PATH}/unicode)
 endif()
+
+# Patch simde neon.h for clang-cl ARM64 compatibility.
+# The MSVC workaround uses intrinsics that clang-cl doesn't provide.
+# TODO: Remove once WebKit is rebuilt with the upstream fix.
+if(WIN32 AND CMAKE_SYSTEM_PROCESSOR MATCHES "ARM64|aarch64|AARCH64")
+  set(SIMDE_NEON_H "${WEBKIT_INCLUDE_PATH}/wtf/simde/arm/neon.h")
+  if(EXISTS "${SIMDE_NEON_H}")
+    file(READ "${SIMDE_NEON_H}" SIMDE_CONTENT)
+    string(REPLACE
+      "(defined _MSC_VER) && (defined SIMDE_ARM_NEON_A64V8_NATIVE)"
+      "(defined _MSC_VER) && !defined(__clang__) && (defined SIMDE_ARM_NEON_A64V8_NATIVE)"
+      SIMDE_CONTENT "${SIMDE_CONTENT}")
+    file(WRITE "${SIMDE_NEON_H}" "${SIMDE_CONTENT}")
+    message(STATUS "Patched simde/arm/neon.h for clang-cl ARM64 compatibility")
+  endif()
+endif()

scripts/build.mjs

@@ -92,21 +92,9 @@ async function build(args) {
     generateOptions["--toolchain"] = toolchainPath;
   }
 
-  // Windows ARM64: automatically set required options
+  // Windows ARM64: log detection (compiler is selected by CMake/toolchain)
   if (isWindowsARM64) {
-    // Use clang-cl instead of MSVC cl.exe for proper ARM64 flag support
-    if (!generateOptions["-DCMAKE_C_COMPILER"]) {
-      generateOptions["-DCMAKE_C_COMPILER"] = "clang-cl";
-    }
-    if (!generateOptions["-DCMAKE_CXX_COMPILER"]) {
-      generateOptions["-DCMAKE_CXX_COMPILER"] = "clang-cl";
-    }
-    // Skip codegen by default since x64 bun crashes under WoW64 emulation
-    // Can be overridden with -DSKIP_CODEGEN=OFF once ARM64 bun is available
-    if (!generateOptions["-DSKIP_CODEGEN"]) {
-      generateOptions["-DSKIP_CODEGEN"] = "ON";
-    }
-    console.log("Windows ARM64 detected: using clang-cl and SKIP_CODEGEN=ON");
+    console.log("Windows ARM64 detected");
   }
 
   const generateArgs = Object.entries(generateOptions).flatMap(([flag, value]) =>

src/bun.js/bindings/highway_strings.cpp

@@ -81,19 +81,6 @@ size_t IndexOfAnyCharImpl(const uint8_t* HWY_RESTRICT text, size_t text_len, con
     } else {
         ASSERT(chars_len <= 16);
 
-        // Use FixedTag to preload search characters into fixed-size vectors.
-        // ScalableTag vectors (SVE) are sizeless and cannot be stored in arrays.
-        // FixedTag gives us a known compile-time size that can be stored in arrays,
-        // then ResizeBitCast converts back to scalable vectors in the inner loop.
-        static constexpr size_t kMaxPreloadedChars = 16;
-        const hn::FixedTag<uint8_t, 16> d_fixed;
-        using VecFixed = hn::Vec<decltype(d_fixed)>;
-        VecFixed char_vecs[kMaxPreloadedChars];
-        const size_t num_chars_to_preload = std::min(chars_len, kMaxPreloadedChars);
-        for (size_t c = 0; c < num_chars_to_preload; ++c) {
-            char_vecs[c] = hn::Set(d_fixed, chars[c]);
-        }
-
         const size_t simd_text_len = text_len - (text_len % N);
         size_t i = 0;
 
@@ -101,8 +88,12 @@ size_t IndexOfAnyCharImpl(const uint8_t* HWY_RESTRICT text, size_t text_len, con
             const auto text_vec = hn::LoadN(d, text + i, N);
             auto found_mask = hn::MaskFalse(d);
 
-            for (size_t c = 0; c < num_chars_to_preload; ++c) {
-                found_mask = hn::Or(found_mask, hn::Eq(text_vec, hn::ResizeBitCast(d, char_vecs[c])));
+            // Broadcast and compare each search character individually.
+            // Cannot preload into a Vec array because SVE types are sizeless.
+            // hn::Set is a single broadcast instruction; the compiler will
+            // hoist these loop-invariant broadcasts out of the outer loop.
+            for (size_t c = 0; c < chars_len; ++c) {
+                found_mask = hn::Or(found_mask, hn::Eq(text_vec, hn::Set(d, chars[c])));
             }
 
             const intptr_t pos = hn::FindFirstTrue(d, found_mask);