[clang] [libunwind] [libunwind][WebAssembly] Make libunwind compilable (PR #92192)

[Heejin Ahn via cfe-commits]

https://github.com/aheejin created https://github.com/llvm/llvm-project/pull/92192

This tries to make Wasm compilable in LLVM tree with CMake for non-Emscripten platform.

This
- Adds `-D__USING_WASM_EXCEPTIONS__` when you compile with `-fwasm-exceptions` (like other EH options) in Clang
- Exclude `UnwindLevel1.c` when compiling with Wasm
- Changed some `__USING_WASM_EXCEPTIONS__` to `__wasm__`; they should be applied when compiling with Wasm w/o exceptions.
- Define some unused macros to make it compile

>From 95b9e56ac8bdd3b0bde08f63f64e35d47a61b784 Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin at gmail.com>
Date: Tue, 14 May 2024 22:08:20 +0000
Subject: [PATCH] [libunwind][WebAssembly] Make libunwind compilable

This tries to make Wasm compilable in LLVM tree with CMake for
non-Emscripten platform.

This
- Adds `-D__USING_WASM_EXCEPTIONS__` when you compile with
  `-fwasm-exceptions` (like other EH options) in Clang
- Exclude `UnwindLevel1.c` when compiling with Wasm
- Changed some `__USING_WASM_EXCEPTIONS__` to `__wasm__`; they should be
  applied when compiling with Wasm w/o exceptions.
- Define some unused macros to make it compile
---
 clang/lib/Frontend/InitPreprocessor.cpp | 2 ++
 libunwind/cmake/config-ix.cmake         | 1 +
 libunwind/include/__libunwind_config.h  | 4 ++++
 libunwind/src/UnwindLevel1.c            | 3 ++-
 libunwind/src/libunwind.cpp             | 4 ++--
 5 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index c1d209466ffe5..3cc85ff502776 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -1006,6 +1006,8 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
   else if (LangOpts.hasDWARFExceptions() &&
            (TI.getTriple().isThumb() || TI.getTriple().isARM()))
     Builder.defineMacro("__ARM_DWARF_EH__");
+  else if (LangOpts.hasWasmExceptions())
+    Builder.defineMacro("__USING_WASM_EXCEPTIONS__");
 
   if (LangOpts.Deprecated)
     Builder.defineMacro("__DEPRECATED");
diff --git a/libunwind/cmake/config-ix.cmake b/libunwind/cmake/config-ix.cmake
index 126c872f0d489..d505ee1d346fa 100644
--- a/libunwind/cmake/config-ix.cmake
+++ b/libunwind/cmake/config-ix.cmake
@@ -109,6 +109,7 @@ check_cxx_compiler_flag(-nostdinc++ CXX_SUPPORTS_NOSTDINCXX_FLAG)
 check_symbol_exists(__arm__ "" LIBUNWIND_TARGET_ARM)
 check_symbol_exists(__USING_SJLJ_EXCEPTIONS__ "" LIBUNWIND_USES_SJLJ_EXCEPTIONS)
 check_symbol_exists(__ARM_DWARF_EH__ "" LIBUNWIND_USES_DWARF_EH)
+check_symbol_exists(__USING_WASM_EXCEPTIONS__ "" LIBUNWIND_USES_WASM_EXCEPTIONS)
 
 if(LIBUNWIND_TARGET_ARM AND NOT LIBUNWIND_USES_SJLJ_EXCEPTIONS AND NOT LIBUNWIND_USES_DWARF_EH)
   # This condition is copied from __libunwind_config.h
diff --git a/libunwind/include/__libunwind_config.h b/libunwind/include/__libunwind_config.h
index 8db336b2d727c..7d87831a80446 100644
--- a/libunwind/include/__libunwind_config.h
+++ b/libunwind/include/__libunwind_config.h
@@ -180,6 +180,10 @@
 #endif
 #define _LIBUNWIND_HIGHEST_DWARF_REGISTER                                      \
   _LIBUNWIND_HIGHEST_DWARF_REGISTER_LOONGARCH
+#elif defined(__wasm__)
+// Unused
+# define _LIBUNWIND_CONTEXT_SIZE 0
+# define _LIBUNWIND_CURSOR_SIZE 0
 # else
 #  error "Unsupported architecture."
 # endif
diff --git a/libunwind/src/UnwindLevel1.c b/libunwind/src/UnwindLevel1.c
index 05d0f2cb0a0a7..48e7bc3b9e00e 100644
--- a/libunwind/src/UnwindLevel1.c
+++ b/libunwind/src/UnwindLevel1.c
@@ -31,7 +31,8 @@
 #include "libunwind_ext.h"
 #include "unwind.h"
 
-#if !defined(_LIBUNWIND_ARM_EHABI) && !defined(__USING_SJLJ_EXCEPTIONS__)
+#if !defined(_LIBUNWIND_ARM_EHABI) && !defined(__USING_SJLJ_EXCEPTIONS__) &&   \
+    !defined(__wasm__)
 
 #ifndef _LIBUNWIND_SUPPORT_SEH_UNWIND
 
diff --git a/libunwind/src/libunwind.cpp b/libunwind/src/libunwind.cpp
index 217dde9098637..7e5c6bd263e14 100644
--- a/libunwind/src/libunwind.cpp
+++ b/libunwind/src/libunwind.cpp
@@ -26,7 +26,7 @@
 #include <sanitizer/asan_interface.h>
 #endif
 
-#if !defined(__USING_SJLJ_EXCEPTIONS__) && !defined(__USING_WASM_EXCEPTIONS__)
+#if !defined(__USING_SJLJ_EXCEPTIONS__) && !defined(__wasm__)
 #include "AddressSpace.hpp"
 #include "UnwindCursor.hpp"
 
@@ -348,7 +348,7 @@ void __unw_remove_dynamic_eh_frame_section(unw_word_t eh_frame_start) {
 
 #endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
 #endif // !defined(__USING_SJLJ_EXCEPTIONS__) &&
-       // !defined(__USING_WASM_EXCEPTIONS__)
+       // !defined(__wasm__)
 
 #ifdef __APPLE__