When targeting WASM, allow memory growth and code gen that could trap.

CMake/Modules/UrhoCommon.cmake

@@ -292,12 +292,12 @@ endif ()
 if (EMSCRIPTEN)     # CMAKE_CROSSCOMPILING is always true for Emscripten
     set (EMSCRIPTEN_ROOT_PATH "" CACHE PATH "Root path to Emscripten cross-compiler tools (Emscripten only)")
     set (EMSCRIPTEN_SYSROOT "" CACHE PATH "Path to Emscripten system root (Emscripten only)")
-    option (EMSCRIPTEN_ALLOW_MEMORY_GROWTH "Enable memory growing based on application demand (Emscripten only)")
-    math (EXPR EMSCRIPTEN_TOTAL_MEMORY "128 * 1024 * 1024")     # This option is ignored when EMSCRIPTEN_ALLOW_MEMORY_GROWTH option is set
-    set (EMSCRIPTEN_TOTAL_MEMORY ${EMSCRIPTEN_TOTAL_MEMORY} CACHE STRING "Specify the total size of memory to be used (Emscripten only); default to 128 MB, this option is ignored when EMSCRIPTEN_ALLOW_MEMORY_GROWTH=1")
+    cmake_dependent_option (EMSCRIPTEN_WASM "Enable Binaryen support to generate output to WASM (WebAssembly) format (Emscripten only)" FALSE "NOT EMSCRIPTEN_EMCC_VERSION VERSION_LESS 1.37.3" FALSE)
+    cmake_dependent_option (EMSCRIPTEN_ALLOW_MEMORY_GROWTH "Enable memory growing based on application demand when targeting asm.js, it is not set by default due to performance penalty (Emscripten only)" FALSE "NOT EMSCRIPTEN_WASM" TRUE)   # Allo memory growth by default when targeting WebAssembly since there is no performance penalty as in asm.js mode
+    math (EXPR EMSCRIPTEN_TOTAL_MEMORY "128 * 1024 * 1024")
+    set (EMSCRIPTEN_TOTAL_MEMORY ${EMSCRIPTEN_TOTAL_MEMORY} CACHE STRING "Specify the total size of memory to be used (Emscripten only); default to 128 MB, must be in multiple of 64 KB when targeting WebAssembly and in multiple of 16 MB when targeting asm.js")
     option (EMSCRIPTEN_SHARE_DATA "Enable sharing data file support (Emscripten only)")
     cmake_dependent_option (EMSCRIPTEN_SHARE_JS "Share the same JS file responsible to load the shared data file (Emscripten only and when enabling sharing data file support only)" FALSE EMSCRIPTEN_SHARE_DATA FALSE)
-    cmake_dependent_option (EMSCRIPTEN_WASM "Enable Binaryen support to generate output to WASM (WebAssembly) format (Emscripten only)" FALSE "NOT EMSCRIPTEN_EMCC_VERSION VERSION_LESS 1.37.3" FALSE)
 endif ()
 # Constrain the build option values in cmake-gui, if applicable
 set_property (CACHE URHO3D_LIB_TYPE PROPERTY STRINGS STATIC SHARED)
@@ -629,15 +629,15 @@ else ()
                 set (CMAKE_C_FLAGS_RELEASE "-Oz -DNDEBUG")
                 set (CMAKE_CXX_FLAGS_RELEASE "-Oz -DNDEBUG")
                 # Linker flags
-                if (EMSCRIPTEN_ALLOW_MEMORY_GROWTH)
-                    set (MEMORY_LINKER_FLAGS "-s ALLOW_MEMORY_GROWTH=1")
-                else ()
-                    set (MEMORY_LINKER_FLAGS "-s TOTAL_MEMORY=${EMSCRIPTEN_TOTAL_MEMORY}")
-                endif ()
                 if (EMSCRIPTEN_WASM)
-                    set (WASM "-s WASM=1")
+                    # Allow emitting of code that might trap (for higher performance)
+                    set (WASM_LINKER_FLAGS "-s WASM=1 -s BINARYEN_IMPRECISE=1")  # TODO: BINARYEN_IMPRECISE could be renamed to BINARYEN_EMIT_POTENTIAL_TRAPS or something like that in the coming release)
+                endif ()
+                set (MEMORY_LINKER_FLAGS "-s TOTAL_MEMORY=${EMSCRIPTEN_TOTAL_MEMORY}")
+                if (EMSCRIPTEN_ALLOW_MEMORY_GROWTH)
+                    set (MEMORY_LINKER_FLAGS "${MEMORY_LINKER_FLAGS} -s ALLOW_MEMORY_GROWTH=1")
                 endif ()
-                set (CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${MEMORY_LINKER_FLAGS} -s NO_EXIT_RUNTIME=1 -s ERROR_ON_UNDEFINED_SYMBOLS=1 ${WASM}")
+                set (CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${WASM_LINKER_FLAGS} ${MEMORY_LINKER_FLAGS} -s NO_EXIT_RUNTIME=1 -s ERROR_ON_UNDEFINED_SYMBOLS=1")
                 set (CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} -O3 -s AGGRESSIVE_VARIABLE_ELIMINATION=1")     # Remove variables to make the -O3 regalloc easier
                 set (CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -g4")     # Preserve LLVM debug information, show line number debug comments, and generate source maps
                 if (URHO3D_TESTING)

Docs/GettingStarted.dox

@@ -162,11 +162,11 @@ A number of build options can be defined when invoking the build scripts or when
 |ARM_ABI_FLAGS        |-|Specify ABI compiler flags (ARM on Linux platform only); e.g. Orange-Pi Mini 2 could use '-mcpu=cortex-a7 -mfpu=neon-vfpv4'|
 |EMSCRIPTEN_ROOT_PATH |-|Root path to Emscripten cross-compiler tools (Emscripten only)|
 |EMSCRIPTEN_SYSROOT   |-|Path to Emscripten system root (Emscripten only)|
-|EMSCRIPTEN_ALLOW_MEMORY_GROWTH|0|Enable memory growing based on application demand (Emscripten only)|
-|EMSCRIPTEN_TOTAL_MEMORY|*|Specify the total size of memory to be used (Emscripten only); default to 128 MB, this option is ignored when EMSCRIPTEN_ALLOW_MEMORY_GROWTH=1|
+|EMSCRIPTEN_WASM      |0|Enable Binaryen support to generate output to WASM (WebAssembly) format (Emscripten only)|
+|EMSCRIPTEN_ALLOW_MEMORY_GROWTH|*|Enable memory growing based on application demand when targeting asm.js, it is not set by default due to performance penalty (Emscripten only)|
+|EMSCRIPTEN_TOTAL_MEMORY|*|Specify the total size of memory to be used (Emscripten only); default to 128 MB, must be in multiple of 64 KB when targeting WebAssembly and in multiple of 16 MB when targeting asm.js|
 |EMSCRIPTEN_SHARE_DATA|0|Enable sharing data file support (Emscripten only)|
 |EMSCRIPTEN_SHARE_JS  |0|Share the same JS file responsible to load the shared data file (Emscripten only and when enabling sharing data file support only)|
-|EMSCRIPTEN_WASM      |0|Enable Binaryen support to generate output to WASM (WebAssembly) format (Emscripten only)|
 |EMSCRIPTEN_EMRUN_BROWSER|firefox|Specify the particular browser to be spawned by emrun during testing (Emscripten only), use 'emrun --list_browsers' command to get the list of possible values|
 
 Note that the specified build option values are cached by CMake after the initial configuration step. The cached values will be used by CMake in the subsequent configuration. The same build options are not required to be specified again and again. But once a non-default build option value is being cached, it can only be reverted back to its default value by explicitly resetting it. That is, simply by not passing the corresponding build option would not revert it back to its default. One way to revert all the build options to their default values is by clearing the CMake cache by executing cmake_clean.bat or cmake_clean.sh with the location of the build tree as the first argument or by executing it in the build tree itself.