[win][arm64ec] Fixes to unblock building LLVM and Clang as Arm64EC (#150068)

dpaoliello · web-flow · commit 4adce336f462 · 2025-07-31T09:30:05.000-07:00
These changes allow LLVM and Clang to be built with Clang targeting
Arm64EC using the MSVC linker.

Built with these options:
```
-DLLVM_ENABLE_PROJECTS="clang"
-DLLVM_HOST_TRIPLE=arm64ec-pc-windows-msvc
-DCMAKE_C_COMPILER=clang-cl.exe
-DCMAKE_C_COMPILER_TARGET=arm64ec-pc-windows-msvc
-DCMAKE_CXX_COMPILER=clang-cl.exe
-DCMAKE_CXX_COMPILER_TARGET=arm64ec-pc-windows-msvc
-DCMAKE_LINKER_TYPE=MSVC
```
diff --git a/clang/tools/clang-repl/CMakeLists.txt b/clang/tools/clang-repl/CMakeLists.txt
@@ -19,14 +19,14 @@ if(MSVC)
   set_target_properties(clang-repl PROPERTIES WINDOWS_EXPORT_ALL_SYMBOLS 1)
 
   # RTTI/C++ symbols
-  set(clang_repl_exports ${clang_repl_exports} ??_7type_info@@6B@
-    ?__type_info_root_node@@3U__type_info_node@@A
-    ?nothrow@std@@3Unothrow_t@1@B
+  set(clang_repl_exports ${clang_repl_exports} ??_7type_info@@6B@,DATA
+    ?__type_info_root_node@@3U__type_info_node@@A,DATA
+    ?nothrow@std@@3Unothrow_t@1@B,DATA
   )
 
   # Compiler added symbols for static variables. NOT for VStudio < 2015
-  set(clang_repl_exports ${clang_repl_exports} _Init_thread_abort _Init_thread_epoch
-    _Init_thread_footer _Init_thread_header _tls_index
+  set(clang_repl_exports ${clang_repl_exports} _Init_thread_abort _Init_thread_epoch,DATA
+    _Init_thread_footer _Init_thread_header _tls_index,DATA
   )
 
   if(CMAKE_SIZEOF_VOID_P EQUAL 8)
@@ -50,7 +50,10 @@ if(MSVC)
   endif()
 
   # List to '/EXPORT:sym0 /EXPORT:sym1 /EXPORT:sym2 ...'
-  list(TRANSFORM clang_repl_exports PREPEND "LINKER:/EXPORT:")
+  # The 'SHELL' prefix tells CMake to use a space instead of comma as the
+  # separator between the driver and linker options, which we need since MSVC's
+  # linker uses `,DATA` as a suffix to indicate that data is being exported.
+  list(TRANSFORM clang_repl_exports PREPEND "LINKER:SHELL:/EXPORT:")
 
   set_property(TARGET clang-repl APPEND PROPERTY LINK_OPTIONS ${clang_repl_exports})
 
diff --git a/llvm/lib/Support/BLAKE3/CMakeLists.txt b/llvm/lib/Support/BLAKE3/CMakeLists.txt
@@ -26,7 +26,8 @@ endmacro()
 if (CAN_USE_ASSEMBLER)
   if (MSVC)
     check_symbol_exists(_M_X64 "" IS_X64)
-    if (IS_X64)
+    check_symbol_exists(_M_ARM64EC "" IS_ARM64EC)
+    if (IS_X64 AND NOT IS_ARM64EC)
       enable_language(ASM_MASM)
       set(LLVM_BLAKE3_ASM_FILES
         blake3_sse2_x86-64_windows_msvc.asm
diff --git a/llvm/lib/TargetParser/Host.cpp b/llvm/lib/TargetParser/Host.cpp
@@ -587,8 +587,9 @@ StringRef sys::detail::getHostCPUNameForBPF() {
 #endif
 }
 
-#if defined(__i386__) || defined(_M_IX86) || defined(__x86_64__) ||            \
-    defined(_M_X64)
+#if (defined(__i386__) || defined(_M_IX86) || defined(__x86_64__) ||           \
+     defined(_M_X64)) &&                                                       \
+    !defined(_M_ARM64EC)
 
 /// getX86CpuIDAndInfo - Execute the specified cpuid and return the 4 values in
 /// the specified arguments.  If we can't run cpuid on the host, return true.
@@ -1853,8 +1854,9 @@ VendorSignatures getVendorSignature(unsigned *MaxLeaf) {
 } // namespace llvm
 #endif
 
-#if defined(__i386__) || defined(_M_IX86) || \
-    defined(__x86_64__) || defined(_M_X64)
+#if (defined(__i386__) || defined(_M_IX86) || defined(__x86_64__) ||           \
+     defined(_M_X64)) &&                                                       \
+    !defined(_M_ARM64EC)
 StringMap<bool> sys::getHostCPUFeatures() {
   unsigned EAX = 0, EBX = 0, ECX = 0, EDX = 0;
   unsigned MaxLevel;
@@ -2147,7 +2149,8 @@ StringMap<bool> sys::getHostCPUFeatures() {
 
   return Features;
 }
-#elif defined(_WIN32) && (defined(__aarch64__) || defined(_M_ARM64))
+#elif defined(_WIN32) && (defined(__aarch64__) || defined(_M_ARM64) ||         \
+                          defined(__arm64ec__) || defined(_M_ARM64EC))
 StringMap<bool> sys::getHostCPUFeatures() {
   StringMap<bool> Features;
 
diff --git a/llvm/tools/llvm-exegesis/lib/X86/Target.cpp b/llvm/tools/llvm-exegesis/lib/X86/Target.cpp
@@ -30,11 +30,12 @@
 #include <memory>
 #include <string>
 #include <vector>
-#if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
+#if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64)) &&              \
+    !defined(_M_ARM64EC)
 #include <immintrin.h>
 #include <intrin.h>
 #endif
-#if defined(_MSC_VER) && defined(_M_X64)
+#if defined(_MSC_VER) && defined(_M_X64) && !defined(_M_ARM64EC)
 #include <float.h> // For _clearfp in ~X86SavedState().
 #endif
 
@@ -654,7 +655,7 @@ namespace {
 class X86SavedState : public ExegesisTarget::SavedState {
 public:
   X86SavedState() {
-#if defined(_MSC_VER) && defined(_M_X64)
+#if defined(_MSC_VER) && defined(_M_X64) && !defined(_M_ARM64EC)
     _fxsave64(FPState);
     Eflags = __readeflags();
 #elif defined(__GNUC__) && defined(__x86_64__)
@@ -668,7 +669,7 @@ class X86SavedState : public ExegesisTarget::SavedState {
   ~X86SavedState() {
     // Restoring the X87 state does not flush pending exceptions, make sure
     // these exceptions are flushed now.
-#if defined(_MSC_VER) && defined(_M_X64)
+#if defined(_MSC_VER) && defined(_M_X64) && !defined(_M_ARM64EC)
     _clearfp();
     _fxrstor64(FPState);
     __writeeflags(Eflags);
@@ -682,7 +683,7 @@ class X86SavedState : public ExegesisTarget::SavedState {
   }
 
 private:
-#if defined(__x86_64__) || defined(_M_X64)
+#if defined(__x86_64__) || defined(_M_X64) && !defined(_M_ARM64EC)
   alignas(16) char FPState[512];
   uint64_t Eflags;
 #endif
@@ -824,8 +825,9 @@ class ExegesisX86Target : public ExegesisTarget {
       // For now, only do the check if we see an Intel machine because
       // the counter uses some intel-specific magic and it could
       // be confuse and think an AMD machine actually has LBR support.
-#if defined(__i386__) || defined(_M_IX86) || defined(__x86_64__) ||            \
-    defined(_M_X64)
+#if (defined(__i386__) || defined(_M_IX86) || defined(__x86_64__) ||           \
+     defined(_M_X64)) &&                                                       \
+    !defined(_M_ARM64EC)
     using namespace sys::detail::x86;
 
     if (getVendorSignature() == VendorSignatures::GENUINE_INTEL)
diff --git a/third-party/benchmark/src/cycleclock.h b/third-party/benchmark/src/cycleclock.h
@@ -79,7 +79,7 @@ inline BENCHMARK_ALWAYS_INLINE int64_t Now() {
   int64_t ret;
   __asm__ volatile("rdtsc" : "=A"(ret));
   return ret;
-#elif defined(__x86_64__) || defined(__amd64__)
+#elif (defined(__x86_64__) || defined(__amd64__)) && !defined(__arm64ec__)
   uint64_t low, high;
   __asm__ volatile("rdtsc" : "=a"(low), "=d"(high));
   return (high << 32) | low;
@@ -139,7 +139,7 @@ inline BENCHMARK_ALWAYS_INLINE int64_t Now() {
   struct timespec ts = {0, 0};
   clock_gettime(CLOCK_MONOTONIC, &ts);
   return static_cast<int64_t>(ts.tv_sec) * 1000000000 + ts.tv_nsec;
-#elif defined(__aarch64__)
+#elif defined(__aarch64__) || defined(__arm64ec__)
   // System timer of ARMv8 runs at a different frequency than the CPU's.
   // The frequency is fixed, typically in the range 1-50MHz.  It can be
   // read at CNTFRQ special register.  We assume the OS has set up
