Update libunwind from LLVM 20.1.8 to 21.1.8 (#26036)

This updates libunwind from 20.1.8 to LLVM 21.1.8:
https://github.com/llvm/llvm-project/releases/tag/llvmorg-21.1.8

Additional change:
- Add `-Wno-c23-extensions` to libunwind's cflags:
0070206
  llvm/llvm-project#125412 removed parameter names
  to suppress `-Wunused-parameter` in their own build system, but this
  causes these errors instead for us:
  ```console
 ../../../system/lib/libunwind/src/Unwind-wasm.c:105:62: error: omitting
the parameter name in a function definition is a C23 extension
[-Werror,-Wc23-extensions]
105 | _LIBUNWIND_EXPORT void _Unwind_SetIP(struct _Unwind_Context *,
uintptr_t) {}
          |
  ```
  This suppresses the warnings.

Author: aheejin

ChangeLog.md

@@ -20,7 +20,7 @@ See docs/process.md for more on how version tagging works.
 
 4.0.24 (in development)
 -----------------------
-- compiler-rt was updated to LLVM 21.1.8. (#26405)
+- compiler-rt and libunwind were updated to LLVM 21.1.8. (#26036 and #26045)
 - A new `-sEXECUTABLE` setting was added which adds a #! line to the resulting
   JavaScript and makes it executable.  This setting defaults to true when the
   output filename has no extension, or ends in `.out` (e.g. `a.out`) (#26085)

system/lib/libunwind/readme.txt

@@ -1,14 +1,14 @@
 LLVM's libunwind
 ----------------
 
-These files are from the llvm-project based on release 20.1.8.
+These files are from the llvm-project based on release 21.1.8.
 
 We maintain a local fork of llvm-project that contains any Emscripten
 specific patches:
 
   https://github.com/emscripten-core/llvm-project
 
-The current patch is based on the emscripten-libs-20 branch.
+The current patch is based on the emscripten-libs-21 branch.
 
 Update Instructions
 -------------------
@@ -20,4 +20,4 @@ Modifications
 
 For a list of changes from upstream see the libunwind files that are part of:
 
-https://github.com/llvm/llvm-project/compare/llvmorg-20.1.8...emscripten-core:emscripten-libs-20
+https://github.com/llvm/llvm-project/compare/llvmorg-21.1.8...emscripten-core:emscripten-libs-21

system/lib/libunwind/src/Registers.hpp

@@ -15,9 +15,9 @@
 #include <stdint.h>
 #include <string.h>
 
-#include "cet_unwind.h"
 #include "config.h"
 #include "libunwind.h"
+#include "shadow_stack_unwind.h"
 
 namespace libunwind {
 
@@ -48,7 +48,7 @@ class _LIBUNWIND_HIDDEN Registers_x86;
 extern "C" void __libunwind_Registers_x86_jumpto(Registers_x86 *);
 
 #if defined(_LIBUNWIND_USE_CET)
-extern "C" void *__libunwind_cet_get_jump_target() {
+extern "C" void *__libunwind_shstk_get_jump_target() {
   return reinterpret_cast<void *>(&__libunwind_Registers_x86_jumpto);
 }
 #endif
@@ -268,7 +268,7 @@ class _LIBUNWIND_HIDDEN Registers_x86_64;
 extern "C" void __libunwind_Registers_x86_64_jumpto(Registers_x86_64 *);
 
 #if defined(_LIBUNWIND_USE_CET)
-extern "C" void *__libunwind_cet_get_jump_target() {
+extern "C" void *__libunwind_shstk_get_jump_target() {
   return reinterpret_cast<void *>(&__libunwind_Registers_x86_64_jumpto);
 }
 #endif
@@ -1817,7 +1817,7 @@ class _LIBUNWIND_HIDDEN Registers_arm64;
 extern "C" void __libunwind_Registers_arm64_jumpto(Registers_arm64 *);
 
 #if defined(_LIBUNWIND_USE_GCS)
-extern "C" void *__libunwind_cet_get_jump_target() {
+extern "C" void *__libunwind_shstk_get_jump_target() {
   return reinterpret_cast<void *>(&__libunwind_Registers_arm64_jumpto);
 }
 #endif
@@ -4126,7 +4126,7 @@ inline reg_t Registers_riscv::getRegister(int regNum) const {
     return _registers[regNum];
   if (regNum == UNW_RISCV_VLENB) {
     reg_t vlenb;
-    __asm__("csrr %0, 0xC22" : "=r"(vlenb));
+    __asm__ volatile("csrr %0, 0xC22" : "=r"(vlenb));
     return vlenb;
   }
   _LIBUNWIND_ABORT("unsupported riscv register");

system/lib/libunwind/src/Unwind-seh.cpp

@@ -51,6 +51,32 @@ static DISPATCHER_CONTEXT *__unw_seh_get_disp_ctx(unw_cursor_t *cursor);
 static void __unw_seh_set_disp_ctx(unw_cursor_t *cursor,
                                    DISPATCHER_CONTEXT *disp);
 
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wgnu-anonymous-struct"
+// Local redefinition of this type; mingw-w64 headers lack the
+// DISPATCHER_CONTEXT_NONVOLREG_ARM64 type as of May 2025, so locally redefine
+// it and use that definition, to avoid needing to test/guess whether the real
+// type is available of not.
+union LOCAL_DISPATCHER_CONTEXT_NONVOLREG_ARM64 {
+  BYTE Buffer[11 * sizeof(DWORD64) + 8 * sizeof(double)];
+
+  struct {
+    DWORD64 GpNvRegs[11];
+    double FpNvRegs[8];
+  };
+};
+
+// Custom data type definition; this type is not defined in WinSDK.
+union LOCAL_DISPATCHER_CONTEXT_NONVOLREG_ARM {
+  BYTE Buffer[8 * sizeof(DWORD) + 8 * sizeof(double)];
+
+  struct {
+    DWORD GpNvRegs[8];
+    double FpNvRegs[8];
+  };
+};
+#pragma clang diagnostic pop
+
 /// Common implementation of SEH-style handler functions used by Itanium-
 /// style frames.  Depending on how and why it was called, it may do one of:
 ///  a) Delegate to the given Itanium-style personality function; or
@@ -148,7 +174,8 @@ _GCC_specific_handler(PEXCEPTION_RECORD ms_exc, PVOID frame, PCONTEXT ms_ctx,
     }
     // FIXME: Indicate target frame in foreign case!
     // phase 2: the clean up phase
-    RtlUnwindEx(frame, (PVOID)disp->ControlPc, ms_exc, exc, ms_ctx, disp->HistoryTable);
+    RtlUnwindEx(frame, (PVOID)disp->ControlPc, ms_exc, exc, disp->ContextRecord,
+                disp->HistoryTable);
     _LIBUNWIND_ABORT("RtlUnwindEx() failed");
   case _URC_INSTALL_CONTEXT: {
     // If we were called by __libunwind_seh_personality(), indicate that
@@ -212,6 +239,21 @@ __libunwind_seh_personality(int version, _Unwind_Action state,
   ms_exc.ExceptionInformation[2] = state;
   DISPATCHER_CONTEXT *disp_ctx =
       __unw_seh_get_disp_ctx((unw_cursor_t *)context);
+#if defined(__aarch64__)
+  LOCAL_DISPATCHER_CONTEXT_NONVOLREG_ARM64 nonvol;
+  memcpy(&nonvol.GpNvRegs, &disp_ctx->ContextRecord->X19,
+         sizeof(nonvol.GpNvRegs));
+  for (int i = 0; i < 8; i++)
+    nonvol.FpNvRegs[i] = disp_ctx->ContextRecord->V[i + 8].D[0];
+  disp_ctx->NonVolatileRegisters = nonvol.Buffer;
+#elif defined(__arm__)
+  LOCAL_DISPATCHER_CONTEXT_NONVOLREG_ARM nonvol;
+  memcpy(&nonvol.GpNvRegs, &disp_ctx->ContextRecord->R4,
+         sizeof(nonvol.GpNvRegs));
+  memcpy(&nonvol.FpNvRegs, &disp_ctx->ContextRecord->D[8],
+         sizeof(nonvol.FpNvRegs));
+  disp_ctx->NonVolatileRegisters = nonvol.Buffer;
+#endif
   _LIBUNWIND_TRACE_UNWINDING("__libunwind_seh_personality() calling "
                              "LanguageHandler %p(%p, %p, %p, %p)",
                              (void *)disp_ctx->LanguageHandler, (void *)&ms_exc,

system/lib/libunwind/src/Unwind-wasm.c

@@ -102,8 +102,7 @@ _LIBUNWIND_EXPORT uintptr_t _Unwind_GetIP(struct _Unwind_Context *context) {
 }
 
 /// Not used in Wasm.
-_LIBUNWIND_EXPORT void _Unwind_SetIP(struct _Unwind_Context *context,
-                                     uintptr_t value) {}
+_LIBUNWIND_EXPORT void _Unwind_SetIP(struct _Unwind_Context *, uintptr_t) {}
 
 /// Called by personality handler to get LSDA for current frame.
 _LIBUNWIND_EXPORT uintptr_t
@@ -115,8 +114,7 @@ _Unwind_GetLanguageSpecificData(struct _Unwind_Context *context) {
 }
 
 /// Not used in Wasm.
-_LIBUNWIND_EXPORT uintptr_t
-_Unwind_GetRegionStart(struct _Unwind_Context *context) {
+_LIBUNWIND_EXPORT uintptr_t _Unwind_GetRegionStart(struct _Unwind_Context *) {
   return 0;
 }