Add implementation of emscripten_memcpy_big based on bulk memory. (#19128)

These new functions live in `libbulkmemory` which only gets included
if bulk memory is enabled (either via `-mbulk-memory` directly or
indirectly via `-pthread).

benchmark results for benchmark.test_memcpy_1mb:

```
 v8:                       mean: 1.666
 v8-bulkmemory:            mean: 1.598
 v8-standalone-bulkmemory: mean: 1.576
 v8-standalone:            mean: 3.197
```

Here we can see the that when bulk memory is enabled its at least as
fast if not faster than the JS version.

v8-standalone doesn't have emscripten_memcpy_big at all is is much
slower, as expected.  By adding `-mbulk-memory` the standalone version
becomes just as fast as the non-standalone.

Author: sbc100

embuilder.py

@@ -28,6 +28,7 @@
 
 # Minimal subset of targets used by CI systems to build enough to useful
 MINIMAL_TASKS = [
+    'libbulkmemory',
     'libcompiler_rt',
     'libcompiler_rt-wasm-sjlj',
     'libc',

emcc.py

@@ -1599,6 +1599,9 @@ def phase_setup(options, state, newargs):
     if '-mbulk-memory' not in newargs:
       newargs += ['-mbulk-memory']
 
+  if settings.SHARED_MEMORY:
+    settings.BULK_MEMORY = 1
+
   if 'DISABLE_EXCEPTION_CATCHING' in user_settings and 'EXCEPTION_CATCHING_ALLOWED' in user_settings:
     # If we get here then the user specified both DISABLE_EXCEPTION_CATCHING and EXCEPTION_CATCHING_ALLOWED
     # on the command line.  This is no longer valid so report either an error or a warning (for
@@ -2434,6 +2437,8 @@ def phase_linker_setup(options, state, newargs):
     settings.JS_LIBRARIES.append((0, shared.path_from_root('src', 'library_wasm_worker.js')))
 
   settings.SUPPORTS_GLOBALTHIS = feature_matrix.caniuse(feature_matrix.Feature.GLOBALTHIS)
+  if not settings.BULK_MEMORY:
+    settings.BULK_MEMORY = feature_matrix.caniuse(feature_matrix.Feature.BULK_MEMORY)
 
   if settings.AUDIO_WORKLET:
     if not settings.SUPPORTS_GLOBALTHIS:
@@ -3565,6 +3570,10 @@ def consume_arg_file():
       settings.DISABLE_EXCEPTION_CATCHING = 1
       settings.DISABLE_EXCEPTION_THROWING = 1
       settings.WASM_EXCEPTIONS = 0
+    elif arg == '-mbulk-memory':
+      settings.BULK_MEMORY = 1
+    elif arg == '-mno-bulk-memory':
+      settings.BULK_MEMORY = 0
     elif arg == '-fexceptions':
       # TODO Currently -fexceptions only means Emscripten EH. Switch to wasm
       # exception handling by default when -fexceptions is given when wasm

src/library.js

@@ -389,9 +389,11 @@ mergeInto(LibraryManager.library, {
   // variant, so we should never emit emscripten_memcpy_big() in the build.
   // In STANDALONE_WASM we avoid the emscripten_memcpy_big dependency so keep
   // the wasm file standalone.
+  // In BULK_MEMORY mode we include native versions of these functions based
+  // on memory.fill and memory.copy.
   // In MAIN_MODULE=1 or EMCC_FORCE_STDLIBS mode all of libc is force included
   // so we cannot override parts of it, and therefore cannot use libc_optz.
-#if (SHRINK_LEVEL < 2 || LINKABLE || process.env.EMCC_FORCE_STDLIBS) && !STANDALONE_WASM
+#if (SHRINK_LEVEL < 2 || LINKABLE || process.env.EMCC_FORCE_STDLIBS) && !STANDALONE_WASM && !BULK_MEMORY
 
 #if MIN_CHROME_VERSION < 45 || MIN_EDGE_VERSION < 14 || MIN_FIREFOX_VERSION < 34 || MIN_IE_VERSION != TARGET_NOT_SUPPORTED || MIN_SAFARI_VERSION < 100101
   // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/copyWithin lists browsers that support TypedArray.prototype.copyWithin, but it

src/settings_internal.js

@@ -256,3 +256,5 @@ var POST_JS_FILES = [];
 
 // Set when -pthread / -sPTHREADS is passed
 var PTHREADS = false;
+
+var BULK_MEMORY = false;

system/lib/libc/emscripten_internal.h

@@ -30,6 +30,7 @@ extern "C" {
 void emscripten_memcpy_big(void* __restrict__ dest,
                            const void* __restrict__ src,
                            size_t n) EM_IMPORT(emscripten_memcpy_big);
+void emscripten_memset_big(void* ptr, char value, size_t n);
 
 void emscripten_notify_memory_growth(size_t memory_index);
 

system/lib/libc/emscripten_memcpy.c

@@ -29,7 +29,7 @@ static void *__memcpy(void *restrict dest, const void *restrict src, size_t n) {
   unsigned char *block_aligned_d_end;
   unsigned char *d_end;
 
-#ifndef EMSCRIPTEN_STANDALONE_WASM
+#if !defined(EMSCRIPTEN_STANDALONE_WASM) || defined(__wasm_bulk_memory__)
   if (n >= 512) {
     emscripten_memcpy_big(dest, src, n);
     return dest;

system/lib/libc/emscripten_memcpy_big.S

@@ -0,0 +1,14 @@
+#ifdef __wasm64__
+#define PTR i64
+#else
+#define PTR i32
+#endif
+
+.globl emscripten_memcpy_big
+emscripten_memcpy_big:
+  .functype emscripten_memcpy_big (PTR, PTR, PTR) -> ()
+  local.get 0
+  local.get 1
+  local.get 2
+  memory.copy 0, 0
+  end_function

system/lib/libc/emscripten_memset.c

@@ -1,23 +1,44 @@
-// XXX EMSCRIPTEN ASAN: build an uninstrumented version of memset
-#if defined(__EMSCRIPTEN__) && defined(__has_feature)
-#if __has_feature(address_sanitizer)
-#define memset __attribute__((no_sanitize("address"))) emscripten_builtin_memset
-#endif
+#include "emscripten_internal.h" // for emscripten_memset_big
+
+#if defined(__has_feature) && __has_feature(address_sanitizer)
+// build an uninstrumented version of memset
+__attribute__((no_sanitize("address"))) void *__musl_memset(void *str, int c, size_t n);
+__attribute__((no_sanitize("address"))) void *__memset(void *str, int c, size_t n);
 #endif
 
-#ifdef EMSCRIPTEN_OPTIMIZE_FOR_OZ
+__attribute__((__weak__)) void *__musl_memset(void *str, int c, size_t n);
+__attribute__((__weak__)) void *__memset(void *str, int c, size_t n);
 
-#include <stddef.h>
+#ifdef EMSCRIPTEN_OPTIMIZE_FOR_OZ
 
-void *memset(void *str, int c, size_t n) {
+void *__memset(void *str, int c, size_t n) {
   unsigned char *s = (unsigned char *)str;
 #pragma clang loop unroll(disable)
   while(n--) *s++ = c;
   return str;
 }
 
+#elif defined(__wasm_bulk_memory__)
+
+#define memset __musl_memset
+#include "musl/src/string/memset.c"
+#undef memset
+
+void *__memset(void *str, int c, size_t n) {
+  if (n >= 512) {
+    emscripten_memset_big(str, c, n);
+    return str;
+  }
+  return __musl_memset(str, c, n);
+}
+
 #else
 
+#define memset __memset
 #include "musl/src/string/memset.c"
+#undef memset
 
 #endif
+
+weak_alias(__memset, emscripten_builtin_memset);
+weak_alias(__memset, memset);

system/lib/libc/emscripten_memset_big.S

@@ -0,0 +1,14 @@
+#ifdef __wasm64__
+#define PTR i64
+#else
+#define PTR i32
+#endif
+
+.globl emscripten_memset_big
+emscripten_memset_big:
+  .functype emscripten_memset_big (PTR, i32, PTR) -> ()
+  local.get 0
+  local.get 1
+  local.get 2
+  memory.fill 0
+  end_function

system/lib/standalone/standalone.c

@@ -152,7 +152,7 @@ int emscripten_resize_heap(size_t size) {
 }
 
 double emscripten_get_now(void) {
-  return (1000 * clock()) / (double)CLOCKS_PER_SEC;
+  return (1000ll * clock()) / (double)CLOCKS_PER_SEC;
 }
 
 // C++ ABI