Initial WebAssembly support.

Fixes Ravenbrook#168.

code/mps.c

@@ -255,6 +255,19 @@
 #include "spw3i6.c"     /* Windows on x86-64 stack probe */
 #include "mpsiw3.c"     /* Windows interface layer extras */
 
+/* Emscripten */
+
+#elif defined(MPS_PF_EMJ3LL) || defined(MPS_PF_EMJ6LL)
+
+#include "lockan.c"     /* generic locks */
+#include "than.c"       /* generic threads manager */
+#include "vman.c"       /* malloc-based pseudo memory mapping */
+#include "protan.c"     /* generic memory protection */
+#include "prmcan.c"     /* generic operating system mutator context */
+#include "prmcanan.c"   /* generic architecture mutator context */
+#include "span.c"       /* generic stack probe */
+
+
 #else
 
 #error "Unknown platform -- can't determine platform specific parts."

code/mpstd.h

@@ -392,6 +392,38 @@
 #define MPS_PF_ALIGN    8
 
 
+#elif defined(__EMSCRIPTEN__) && defined(__wasm32__)
+#if defined(CONFIG_PF_STRING) && ! defined(CONFIG_PF_EMJ3LL)
+#error "specified CONFIG_PF_... inconsistent with detected emj3ll"
+#endif
+#define MPS_PF_EMJ3LL
+#define MPS_PF_STRING   "emj3ll"
+#define MPS_OS_EM
+#define MPS_ARCH_J3
+#define MPS_BUILD_LL
+#define MPS_T_WORD      unsigned long
+#define MPS_T_ULONGEST  unsigned long
+#define MPS_WORD_WIDTH  32
+#define MPS_WORD_SHIFT  5
+#define MPS_PF_ALIGN    4
+
+
+#elif defined(__EMSCRIPTEN__) && defined(__wasm64__)
+#if defined(CONFIG_PF_STRING) && ! defined(CONFIG_PF_EMJ6LL)
+#error "specified CONFIG_PF_... inconsistent with detected emj6ll"
+#endif
+#define MPS_PF_EMJ6LL
+#define MPS_PF_STRING   "emj6ll"
+#define MPS_OS_EM
+#define MPS_ARCH_J6
+#define MPS_BUILD_LL
+#define MPS_T_WORD      unsigned long
+#define MPS_T_ULONGEST  unsigned long
+#define MPS_WORD_WIDTH  64
+#define MPS_WORD_SHIFT  6
+#define MPS_PF_ALIGN    8
+
+
 #else
 #error "The MPS Kit does not have a configuration for this platform out of the box; see manual/build.txt"
 #endif

manual/source/topic/platform.rst

@@ -17,6 +17,7 @@ six-character code breaks down into three pairs of characters:
 ======  ================  ====================
 ``OS``  Operating system  Constant
 ======  ================  ====================
+``em``  Emscripten        :c:macro:`MPS_OS_EM`
 ``fr``  FreeBSD           :c:macro:`MPS_OS_FR`
 ``li``  Linux             :c:macro:`MPS_OS_LI`
 ``w3``  Windows           :c:macro:`MPS_OS_W3`
@@ -31,6 +32,8 @@ The second pair of characters names the processor architecture:
 ``a6``  ARM64                   :c:macro:`MPS_ARCH_A6`
 ``i3``  Intel/AMD IA-32         :c:macro:`MPS_ARCH_I3`
 ``i6``  Intel/AMD x86-64        :c:macro:`MPS_ARCH_I6`
+``j3``  WebAssembly (32 bit)    :c:macro:`MPS_ARCH_WA`
+``j6``  WebAssembly (64 bit)    :c:macro:`MPS_ARCH_WA`
 ======  ======================  ======================
 
 The third pair of characters names the compiler toolchain:
@@ -92,6 +95,20 @@ Platform interface
         The MPS is not supported on IA-64 (Itanium).
 
 
+.. c:macro:: MPS_ARCH_J3
+
+    A :term:`C` preprocessor macro that indicates, if defined, that
+    the target processor architecture of the compilation is 32-bit
+    WebAssembly.
+
+
+.. c:macro:: MPS_ARCH_J6
+
+    A :term:`C` preprocessor macro that indicates, if defined, that
+    the target processor architecture of the compilation is 64-bit
+    WebAssembly.
+
+
 .. c:macro:: MPS_BUILD_GC
 
     A :term:`C` preprocessor macro that indicates, if defined, that
@@ -113,6 +130,12 @@ Platform interface
     Studio.
 
 
+.. c:macro:: MPS_OS_EM
+
+    A :term:`C` preprocessor macro that indicates, if defined, that
+    the MPS was compiled for Emscripten.
+
+
 .. c:macro:: MPS_OS_FR
 
     A :term:`C` preprocessor macro that indicates, if defined, that
@@ -143,6 +166,20 @@ Platform interface
     the :term:`natural alignment` of the :term:`platform`.
 
 
+.. c:macro:: MPS_PF_EMJ3LL
+
+    A :term:`C` preprocessor macro that indicates, if defined, that
+    the :term:`platform` consists of the Emscripten operating environemtn,
+    the 32-bit WebAssembly target architecture, and the Clang/LLVM compiler.
+
+
+.. c:macro:: MPS_PF_EMJ6LL
+
+    A :term:`C` preprocessor macro that indicates, if defined, that
+    the :term:`platform` consists of the Emscripten operating environemtn,
+    the 64-bit WebAssembly target architecture, and the Clang/LLVM compiler.
+
+
 .. c:macro:: MPS_PF_FRI3GC
 
     A :term:`C` preprocessor macro that indicates, if defined, that