Implement atomics wait/notify with C++20 runtime support

WebAssembly · Jul 12, 2023 · 7e2ae21 · 7e2ae21
1 parent e37de9d
commit 7e2ae21
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Showing 17 changed files with 738 additions and 581 deletions.
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
@@ -124,7 +124,9 @@ jobs:
     env:
       USE_NINJA: "1"
       CC: "clang" # used by the wasm2c tests
+      CXX: "clang++" # used by the wasm2c wait/notify runtime
       WASM2C_CFLAGS: "-march=x86-64-v2 -fsanitize=address -DWASM_RT_USE_MMAP=0"
+      WASM2C_CXXFLAGS: "-march=x86-64-v2 -fsanitize=address -DWASM_RT_USE_MMAP=0"
     steps:
     - uses: actions/setup-python@v1
       with:

diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -19,7 +19,13 @@ project(WABT LANGUAGES C CXX VERSION 1.0.33)
 
 include(GNUInstallDirs)
 
+option(BUILD_WASM2C_THREAD_WAIT_NOTIFY "Include wasm2c runtime support for wasm2c's thread wait/notify API (Requires C++ 20)." OFF)
+
+if (BUILD_WASM2C_THREAD_WAIT_NOTIFY)
+set(CMAKE_CXX_STANDARD 20)
+else()
 set(CMAKE_CXX_STANDARD 17)
+endif()
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
@@ -224,6 +230,7 @@ function(sanitizer NAME FLAGS)
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${FLAGS}" PARENT_SCOPE)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${FLAGS}" PARENT_SCOPE)
     set(WASM2C_CFLAGS "${WASM2C_CFLAGS} ${FLAGS}" PARENT_SCOPE)
+    set(WASM2C_CXXFLAGS "${WASM2C_CXXFLAGS} ${FLAGS}" PARENT_SCOPE)
   endif ()
 endfunction()
 sanitizer(USE_ASAN "-fsanitize=address")
@@ -424,6 +431,11 @@ endif ()
 
 if (HAVE_SETJMP_H)
   set(WASM_RT_FILES "wasm2c/wasm-rt-impl.h" "wasm2c/wasm-rt-impl.c" "wasm2c/wasm-rt-exceptions-impl.c")
+  if (BUILD_WASM2C_THREAD_WAIT_NOTIFY)
+    set(WASM_RT_FILES ${WASM_RT_FILES} "wasm2c/wasm-rt-threads-impl.cpp")
+  else()
+    set(WASM_RT_FILES ${WASM_RT_FILES} "wasm2c/wasm-rt-threads-dummy-impl.c")
+  endif()
 
   add_library(wasm-rt-impl STATIC ${WASM_RT_FILES})
   add_library(wabt::wasm-rt-impl ALIAS wasm-rt-impl)
@@ -439,7 +451,7 @@ if (HAVE_SETJMP_H)
       INCLUDES DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
     )
     install(
-      FILES "wasm2c/wasm-rt.h" "wasm2c/wasm-rt-exceptions.h"
+      FILES "wasm2c/wasm-rt.h" "wasm2c/wasm-rt-threads.h" "wasm2c/wasm-rt-exceptions.h"
       TYPE INCLUDE
       COMPONENT wabt-development
     )
@@ -651,10 +663,17 @@ if (BUILD_TESTS)
     set(WASM2C_CFLAGS "${WASM2C_CFLAGS} -isysroot ${CMAKE_OSX_SYSROOT}")
   endif ()
 
+  set(WASM2C_CXXFLAGS "${WASM2C_CFLAGS}")
+
   if (DEFINED ENV{WASM2C_CFLAGS})
     set(WASM2C_CFLAGS "${WASM2C_CFLAGS} $ENV{WASM2C_CFLAGS}")
   endif ()
 
+
+  if (DEFINED ENV{WASM2C_CXXFLAGS})
+    set(WASM2C_CXXFLAGS "${WASM2C_CXXFLAGS} $ENV{WASM2C_CXXFLAGS}")
+  endif ()
+
   set(THREADS_PREFER_PTHREAD_FLAG ON)
   find_package(Threads REQUIRED)
 
@@ -718,7 +737,7 @@ if (BUILD_TESTS)
   set(RUN_TESTS_PY ${WABT_SOURCE_DIR}/test/run-tests.py)
 
   add_custom_target(run-tests
-    COMMAND ${CMAKE_COMMAND} -E env WASM2C_CC=${CMAKE_C_COMPILER} WASM2C_CFLAGS=${WASM2C_CFLAGS} ${PYTHON_EXECUTABLE} ${RUN_TESTS_PY} --bindir $<TARGET_FILE_DIR:wat2wasm>
+    COMMAND ${CMAKE_COMMAND} -E env WASM2C_CC=${CMAKE_C_COMPILER} WASM2C_CXX=${CMAKE_CXX_COMPILER} WASM2C_CFLAGS=${WASM2C_CFLAGS} WASM2C_CXXFLAGS=${WASM2C_CXXFLAGS} ${PYTHON_EXECUTABLE} ${RUN_TESTS_PY} --bindir $<TARGET_FILE_DIR:wat2wasm>
     DEPENDS ${WABT_EXECUTABLES}
     WORKING_DIRECTORY ${WABT_SOURCE_DIR}
     USES_TERMINAL

diff --git a/src/c-writer.cc b/src/c-writer.cc
@@ -441,6 +441,8 @@ class CWriter {
   void Write(const AtomicStoreExpr& expr);
   void Write(const AtomicRmwExpr& expr);
   void Write(const AtomicRmwCmpxchgExpr& expr);
+  void Write(const AtomicWaitExpr& expr);
+  void Write(const AtomicNotifyExpr& expr);
 
   size_t BeginTry(const TryExpr& tryexpr);
   void WriteTryCatch(const TryExpr& tryexpr);
@@ -3593,8 +3595,14 @@ void CWriter::Write(const ExprList& exprs) {
         break;
       }
 
-      case ExprType::AtomicWait:
-      case ExprType::AtomicNotify:
+      case ExprType::AtomicWait: {
+        Write(*cast<AtomicWaitExpr>(&expr));
+        break;
+      }
+      case ExprType::AtomicNotify: {
+        Write(*cast<AtomicNotifyExpr>(&expr));
+        break;
+      }
       case ExprType::ReturnCall:
       case ExprType::ReturnCallIndirect:
       case ExprType::CallRef:
@@ -5350,6 +5358,44 @@ void CWriter::Write(const AtomicRmwCmpxchgExpr& expr) {
   PushType(result_type);
 }
 
+void CWriter::Write(const AtomicWaitExpr& expr) {
+  const char* func = nullptr;
+  // clang-format off
+  switch(expr.opcode) {
+    case Opcode::MemoryAtomicWait32: func = "memory_atomic_wait32"; break;
+    case Opcode::MemoryAtomicWait64: func = "memory_atomic_wait64"; break;
+    default:
+      WABT_UNREACHABLE;
+  }
+  // clang-format on
+
+  Memory* memory = module_->memories[module_->GetMemoryIndex(expr.memidx)];
+  Type result_type = expr.opcode.GetResultType();
+
+  Write(StackVar(2, result_type), " = ", func, "(",
+        ExternalInstancePtr(ModuleFieldType::Memory, memory->name), ", (u64)(",
+        StackVar(2), ")");
+  if (expr.offset != 0)
+    Write(" + ", expr.offset);
+  Write(", ", StackVar(1), ", ", StackVar(0), ");", Newline());
+  DropTypes(3);
+  PushType(result_type);
+}
+
+void CWriter::Write(const AtomicNotifyExpr& expr) {
+  Memory* memory = module_->memories[module_->GetMemoryIndex(expr.memidx)];
+  Type result_type = expr.opcode.GetResultType();
+
+  Write(StackVar(1, result_type), " = memory_atomic_notify(",
+        ExternalInstancePtr(ModuleFieldType::Memory, memory->name), ", (u64)(",
+        StackVar(1), ")");
+  if (expr.offset != 0)
+    Write(" + ", expr.offset);
+  Write(", ", StackVar(0), ");", Newline());
+  DropTypes(2);
+  PushType(result_type);
+}
+
 void CWriter::ReserveExportNames() {
   for (const Export* export_ : module_->exports) {
     ReserveExportName(export_->name);

diff --git a/src/prebuilt/wasm2c_atomicops_source_declarations.cc b/src/prebuilt/wasm2c_atomicops_source_declarations.cc
@@ -1,4 +1,7 @@
-const char* s_atomicops_source_declarations = R"w2c_template(#if defined(_MSC_VER)
+const char* s_atomicops_source_declarations = R"w2c_template(#include "wasm-rt-threads.h"
+)w2c_template"
+R"w2c_template(
+#if defined(_MSC_VER)
 )w2c_template"
 R"w2c_template(
 #include <intrin.h>
@@ -435,4 +438,97 @@ R"w2c_template(DEFINE_ATOMIC_CMP_XCHG(i64_atomic_rmw32_cmpxchg_u, u64, u32);
 )w2c_template"
 R"w2c_template(DEFINE_ATOMIC_CMP_XCHG(i64_atomic_rmw_cmpxchg, u64, u64);
 )w2c_template"
+R"w2c_template(
+/** total number of instances that are waiting on a notify. */
+)w2c_template"
+R"w2c_template(static uint32_t wait_instances = 0;
+)w2c_template"
+R"w2c_template(
+static u32 memory_atomic_wait_helper(wasm_rt_memory_t* mem,
+)w2c_template"
+R"w2c_template(                                     u64 addr,
+)w2c_template"
+R"w2c_template(                                     s64 timeout) {
+)w2c_template"
+R"w2c_template(  uint32_t prev_wait_instances = atomic_add_u32(&wait_instances, 1);
+)w2c_template"
+R"w2c_template(  if (prev_wait_instances == UINT32_MAX - 1) {
+)w2c_template"
+R"w2c_template(    TRAP(MAX_WAITERS);
+)w2c_template"
+R"w2c_template(  }
+)w2c_template"
+R"w2c_template(
+  uint32_t ret = wasm_rt_wait_on_address((uintptr_t)&mem->data[addr], timeout);
+)w2c_template"
+R"w2c_template(  atomic_sub_u32(&wait_instances, 1);
+)w2c_template"
+R"w2c_template(  return ret;
+)w2c_template"
+R"w2c_template(}
+)w2c_template"
+R"w2c_template(
+static u32 memory_atomic_wait32(wasm_rt_memory_t* mem,
+)w2c_template"
+R"w2c_template(                                u64 addr,
+)w2c_template"
+R"w2c_template(                                u32 initial,
+)w2c_template"
+R"w2c_template(                                s64 timeout) {
+)w2c_template"
+R"w2c_template(  ATOMIC_ALIGNMENT_CHECK(addr, u32);
+)w2c_template"
+R"w2c_template(  MEMCHECK(mem, addr, u32);
+)w2c_template"
+R"w2c_template(
+  if (i32_atomic_load(mem, addr) != initial) {
+)w2c_template"
+R"w2c_template(    return 1;  // initial value did not match
+)w2c_template"
+R"w2c_template(  }
+)w2c_template"
+R"w2c_template(
+  return memory_atomic_wait_helper(mem, addr, timeout);
+)w2c_template"
+R"w2c_template(}
+)w2c_template"
+R"w2c_template(
+static u32 memory_atomic_wait64(wasm_rt_memory_t* mem,
+)w2c_template"
+R"w2c_template(                                u64 addr,
+)w2c_template"
+R"w2c_template(                                u64 initial,
+)w2c_template"
+R"w2c_template(                                s64 timeout) {
+)w2c_template"
+R"w2c_template(  ATOMIC_ALIGNMENT_CHECK(addr, u64);
+)w2c_template"
+R"w2c_template(  MEMCHECK(mem, addr, u64);
+)w2c_template"
+R"w2c_template(
+  if (i32_atomic_load(mem, addr) != initial) {
+)w2c_template"
+R"w2c_template(    return 1;  // initial value did not match
+)w2c_template"
+R"w2c_template(  }
+)w2c_template"
+R"w2c_template(
+  return memory_atomic_wait_helper(mem, addr, timeout);
+)w2c_template"
+R"w2c_template(}
+)w2c_template"
+R"w2c_template(
+static u32 memory_atomic_notify(wasm_rt_memory_t* mem, u64 addr, u32 count) {
+)w2c_template"
+R"w2c_template(  ATOMIC_ALIGNMENT_CHECK(addr, u32);
+)w2c_template"
+R"w2c_template(  MEMCHECK(mem, addr, u32);
+)w2c_template"
+R"w2c_template(
+  uint32_t ret = wasm_rt_notify_at_address((uintptr_t)&mem->data[addr], count);
+)w2c_template"
+R"w2c_template(  return ret;
+)w2c_template"
+R"w2c_template(}
+)w2c_template"
 ;
diff --git a/src/template/wasm2c_atomicops.declarations.c b/src/template/wasm2c_atomicops.declarations.c
@@ -1,3 +1,5 @@
+#include "wasm-rt-threads.h"
+
 #if defined(_MSC_VER)
 
 #include <intrin.h>
@@ -236,3 +238,55 @@ DEFINE_ATOMIC_CMP_XCHG(i64_atomic_rmw8_cmpxchg_u, u64, u8);
 DEFINE_ATOMIC_CMP_XCHG(i64_atomic_rmw16_cmpxchg_u, u64, u16);
 DEFINE_ATOMIC_CMP_XCHG(i64_atomic_rmw32_cmpxchg_u, u64, u32);
 DEFINE_ATOMIC_CMP_XCHG(i64_atomic_rmw_cmpxchg, u64, u64);
+
+/** total number of instances that are waiting on a notify. */
+static uint32_t wait_instances = 0;
+
+static u32 memory_atomic_wait_helper(wasm_rt_memory_t* mem,
+                                     u64 addr,
+                                     s64 timeout) {
+  uint32_t prev_wait_instances = atomic_add_u32(&wait_instances, 1);
+  if (prev_wait_instances == UINT32_MAX - 1) {
+    TRAP(MAX_WAITERS);
+  }
+
+  uint32_t ret = wasm_rt_wait_on_address((uintptr_t)&mem->data[addr], timeout);
+  atomic_sub_u32(&wait_instances, 1);
+  return ret;
+}
+
+static u32 memory_atomic_wait32(wasm_rt_memory_t* mem,
+                                u64 addr,
+                                u32 initial,
+                                s64 timeout) {
+  ATOMIC_ALIGNMENT_CHECK(addr, u32);
+  MEMCHECK(mem, addr, u32);
+
+  if (i32_atomic_load(mem, addr) != initial) {
+    return 1;  // initial value did not match
+  }
+
+  return memory_atomic_wait_helper(mem, addr, timeout);
+}
+
+static u32 memory_atomic_wait64(wasm_rt_memory_t* mem,
+                                u64 addr,
+                                u64 initial,
+                                s64 timeout) {
+  ATOMIC_ALIGNMENT_CHECK(addr, u64);
+  MEMCHECK(mem, addr, u64);
+
+  if (i32_atomic_load(mem, addr) != initial) {
+    return 1;  // initial value did not match
+  }
+
+  return memory_atomic_wait_helper(mem, addr, timeout);
+}
+
+static u32 memory_atomic_notify(wasm_rt_memory_t* mem, u64 addr, u32 count) {
+  ATOMIC_ALIGNMENT_CHECK(addr, u32);
+  MEMCHECK(mem, addr, u32);
+
+  uint32_t ret = wasm_rt_notify_at_address((uintptr_t)&mem->data[addr], count);
+  return ret;
+}