diff --git a/src/library.js b/src/library.js
index fbcd89e60e99d..cda307c0775b5 100644
--- a/src/library.js
+++ b/src/library.js
@@ -91,6 +91,7 @@ LibraryManager.library = {
   utime__proxy: 'sync',
   utime__sig: 'iii',
   utime: function(path, times) {
+    {{{ from64('times') }}};
     // int utime(const char *path, const struct utimbuf *times);
     // http://pubs.opengroup.org/onlinepubs/009695399/basedefs/utime.h.html
     var time;
@@ -458,6 +459,7 @@ LibraryManager.library = {
 
   time__sig: 'ii',
   time: function(ptr) {
+    {{{ from64('ptr') }}};
     var ret = (Date.now()/1000)|0;
     if (ptr) {
       {{{ makeSetValue('ptr', 0, 'ret', 'i32') }}};
@@ -3102,6 +3104,7 @@ LibraryManager.library = {
   $readAsmConstArgsArray: '=[]',
   $readAsmConstArgs__deps: ['$readAsmConstArgsArray'],
   $readAsmConstArgs: function(sigPtr, buf) {
+    {{{ from64(['sigPtr', 'buf']) }}};
 #if ASSERTIONS
     // Nobody should have mutated _readAsmConstArgsArray underneath us to be something else than an array.
     assert(Array.isArray(readAsmConstArgsArray));
@@ -3646,20 +3649,23 @@ LibraryManager.library = {
   // mode are created here and imported by the module.
   // Mark with `__import` so these are usable from native code.  This is needed
   // because, by default, only functions can be be imported.
-  __stack_pointer: "new WebAssembly.Global({'value': 'i32', 'mutable': true}, {{{ STACK_BASE }}})",
+  __stack_pointer: "new WebAssembly.Global({'value': '{{{ POINTER_TYPE }}}', 'mutable': true}, {{{ to64(STACK_BASE) }}})",
   __stack_pointer__import: true,
   // tell the memory segments where to place themselves
-  __memory_base: '{{{ GLOBAL_BASE }}}',
+  __memory_base: "new WebAssembly.Global({'value': '{{{ POINTER_TYPE }}}', 'mutable': false}, {{{ to64(GLOBAL_BASE) }}})",
   __memory_base__import: true,
   // the wasm backend reserves slot 0 for the NULL function pointer
-  __table_base: 1,
+  __table_base: "new WebAssembly.Global({'value': '{{{ POINTER_TYPE }}}', 'mutable': false}, {{{ to64(1) }}})",
   __table_base__import: true,
+#if MEMORY64
+  __table_base32: 1,
+#endif
   // To support such allocations during startup, track them on __heap_base and
   // then when the main module is loaded it reads that value and uses it to
   // initialize sbrk (the main module is relocatable itself, and so it does not
   // have __heap_base hardcoded into it - it receives it from JS as an extern
   // global, basically).
-  __heap_base: '{{{ HEAP_BASE }}}',
+  __heap_base: '{{{ to64(HEAP_BASE) }}}',
   __heap_base__import: true,
 #endif
 };
diff --git a/src/library_formatString.js b/src/library_formatString.js
index 77bd3c40ce0f3..c9415c15dde7f 100644
--- a/src/library_formatString.js
+++ b/src/library_formatString.js
@@ -52,6 +52,7 @@ mergeInto(LibraryManager.library, {
 #endif
   ],
   $formatString: function(format, varargs) {
+    {{{ from64(['format', 'varargs']) }}};
 #if ASSERTIONS
     assert((varargs & 3) === 0);
 #endif
@@ -470,6 +471,7 @@ mergeInto(LibraryManager.library, {
   // printf/puts/strlen implementations for when musl is not pulled in - very
   // partial. useful for tests, and when bootstrapping structInfo
   strlen: function(ptr) {
+    {{{ from64('ptr') }}};
     var end = ptr;
     while (HEAPU8[end]) ++end;
     return end - ptr;
diff --git a/src/parseTools.js b/src/parseTools.js
index 8479895e5d389..35e8ad0f3fc09 100644
--- a/src/parseTools.js
+++ b/src/parseTools.js
@@ -197,10 +197,20 @@ function isStructPointerType(type) {
   return !Compiletime.isNumberType(type) && type[0] == '%';
 }
 
+const POINTER_SIZE = MEMORY64 ? 8 : 4;
+const POINTER_BITS = POINTER_SIZE * 8;
+const POINTER_TYPE = 'i' + POINTER_BITS;
+
+const SIZE_TYPE = POINTER_TYPE;
+
 function isPointerType(type) {
   return type[type.length - 1] == '*';
 }
 
+function sizeT(x) {
+  return MEMORY64 ? `BigInt(${x})` : x;
+}
+
 function isArrayType(type) {
   return /^\[\d+\ x\ (.*)\]/.test(type);
 }
@@ -235,7 +245,7 @@ function isIntImplemented(type) {
 
 // Note: works for iX types and structure types, not pointers (even though they are implemented as ints)
 function getBits(type, allowPointers) {
-  if (allowPointers && isPointerType(type)) return 32;
+  if (allowPointers && isPointerType(type)) return POINTER_SIZE;
   if (!type) return 0;
   if (type[0] == 'i') {
     const left = type.substr(1);
@@ -480,7 +490,7 @@ function checkSafeHeap() {
 }
 
 function getHeapOffset(offset, type) {
-  if (type == 'i64') {
+  if (!WASM_BIGINT && Runtime.getNativeFieldSize(type) > 4 && type == 'i64') {
     // we emulate 64-bit integer values as 32 in asmjs-unknown-emscripten, but not double
     type = 'i32';
   }
@@ -623,7 +633,16 @@ function makeGetValue(ptr, pos, type, noNeedFirst, unsigned, ignore, align, noSa
       return asmCoercion('SAFE_HEAP_LOAD' + ((type in Compiletime.FLOAT_TYPES) ? '_D' : '') + '(' + asmCoercion(offset, 'i32') + ', ' + Runtime.getNativeTypeSize(type) + ', ' + (!!unsigned + 0) + ')', type, unsigned ? 'u' : undefined);
     }
   }
-  return getHeapForType(type, unsigned) + '[' + getHeapOffset(offset, type) + ']';
+
+  const slab = getHeapForType(type, unsigned);
+  let ret = slab + '[' + getHeapOffset(offset, type) + ']';
+  if (slab.substr(slab.length - 2) == '64') {
+    ret = `Number(${ret})`;
+  }
+  if (forceAsm) {
+    ret = asmCoercion(ret, type);
+  }
+  return ret;
 }
 
 /**
@@ -665,7 +684,7 @@ function makeSetValue(ptr, pos, value, type, noNeedFirst, ignore, align, noSafe,
     return '(' + makeSetTempDouble(0, 'double', value) + ',' +
             makeSetValue(ptr, pos, makeGetTempDouble(0, 'i32'), 'i32', noNeedFirst, ignore, align, noSafe, ',') + ',' +
             makeSetValue(ptr, getFastValue(pos, '+', Runtime.getNativeTypeSize('i32')), makeGetTempDouble(1, 'i32'), 'i32', noNeedFirst, ignore, align, noSafe, ',') + ')';
-  } else if (type == 'i64') {
+  } else if (!WASM_BIGINT && type == 'i64') {
     return '(tempI64 = [' + splitI64(value) + '],' +
             makeSetValue(ptr, pos, 'tempI64[0]', 'i32', noNeedFirst, ignore, align, noSafe, ',') + ',' +
             makeSetValue(ptr, getFastValue(pos, '+', Runtime.getNativeTypeSize('i32')), 'tempI64[1]', 'i32', noNeedFirst, ignore, align, noSafe, ',') + ')';
@@ -705,7 +724,12 @@ function makeSetValue(ptr, pos, value, type, noNeedFirst, ignore, align, noSafe,
       return 'SAFE_HEAP_STORE' + ((type in Compiletime.FLOAT_TYPES) ? '_D' : '') + '(' + asmCoercion(offset, 'i32') + ', ' + asmCoercion(value, type) + ', ' + Runtime.getNativeTypeSize(type) + ')';
     }
   }
-  return getHeapForType(type) + '[' + getHeapOffset(offset, type) + '] = ' + value;
+
+  const slab = getHeapForType(type);
+  if (slab == 'HEAPU64' || slab == 'HEAP64') {
+    value = `BigInt(${value})`;
+  }
+  return slab + '[' + getHeapOffset(offset, type) + '] = ' + value;
 }
 
 const UNROLL_LOOP_MAX = 8;
@@ -862,13 +886,15 @@ function getFastValue(a, op, b, type) {
 
 function calcFastOffset(ptr, pos, noNeedFirst) {
   assert(!noNeedFirst);
+  if (typeof ptr == 'bigint') ptr = Number(ptr);
+  if (typeof pos == 'bigint') pos = Number(pos);
   return getFastValue(ptr, '+', pos, 'i32');
 }
 
 function getHeapForType(type, unsigned) {
   assert(type);
   if (isPointerType(type)) {
-    type = 'i32'; // Hardcoded 32-bit
+    type = POINTER_TYPE;
   }
   switch (type) {
     case 'i1':
@@ -876,9 +902,13 @@ function getHeapForType(type, unsigned) {
       return unsigned ? 'HEAPU8' : 'HEAP8';
     case 'i16':
       return unsigned ? 'HEAPU16' : 'HEAP16';
+    case 'i64':
+      if (WASM_BIGINT) {
+        return unsigned ? 'HEAPU64' : 'HEAP64';
+      }
+      // fall through
     case '<4 x i32>':
     case 'i32':
-    case 'i64':
       return unsigned ? 'HEAPU32' : 'HEAP32';
     case 'double':
       return 'HEAPF64';
@@ -908,10 +938,7 @@ function makeThrow(what) {
 }
 
 function makeSignOp(value, type, op, force, ignore) {
-  if (type == 'i64') {
-    return value; // these are always assumed to be two 32-bit unsigneds.
-  }
-  if (isPointerType(type)) type = 'i32'; // Pointers are treated as 32-bit ints
+  if (isPointerType(type)) type = POINTER_TYPE;
   if (!value) return value;
   let bits;
   let full;
@@ -1292,6 +1319,26 @@ function sendI64Argument(low, high) {
   return low + ', ' + high;
 }
 
+// Any function called from wasm64 may have bigint args, this function takes
+// a list of variable names to convert to number.
+function from64(x) {
+  if (!MEMORY64) {
+    return '';
+  }
+  if (Array.isArray(x)) {
+    let ret = '';
+    for (e of x) ret += from64(e);
+    return ret;
+  } else {
+    return `${x} = Number(${x});`;
+  }
+}
+
+function to64(x) {
+  if (!MEMORY64) return x;
+  return `BigInt(${x})`;
+}
+
 // Add assertions to catch common errors when using the Promise object we
 // create on Module.ready() and return from MODULARIZE Module() invocations.
 function addReadyPromiseAssertions(promise) {
diff --git a/src/postamble.js b/src/postamble.js
index 15f87d8883fca..0fdd070f49db6 100644
--- a/src/postamble.js
+++ b/src/postamble.js
@@ -215,7 +215,7 @@ function stackCheckInit() {
   // here.
   // TODO(sbc): Move writeStackCookie to native to to avoid this.
 #if RELOCATABLE
-  _emscripten_stack_set_limits({{{ STACK_BASE }}}, {{{ STACK_MAX }}});
+  _emscripten_stack_set_limits({{{ to64(STACK_BASE) }}}, {{{ to64(STACK_MAX) }}});
 #else
   _emscripten_stack_init();
 #endif
diff --git a/src/runtime_strings.js b/src/runtime_strings.js
index 63d599e1bd70c..396d731413186 100644
--- a/src/runtime_strings.js
+++ b/src/runtime_strings.js
@@ -128,6 +128,7 @@ function UTF8ArrayToString(heap, idx, maxBytesToRead) {
  * @return {string}
  */
 function UTF8ToString(ptr, maxBytesToRead) {
+  {{{ from64('ptr') }}};
 #if CAN_ADDRESS_2GB
   ptr >>>= 0;
 #endif
diff --git a/src/settings.js b/src/settings.js
index af7aee12731a2..172cb6f6bba3d 100644
--- a/src/settings.js
+++ b/src/settings.js
@@ -237,6 +237,7 @@ var MEMORY_GROWTH_LINEAR_STEP = -1;
 // the full end-to-end wasm64 mode, and 2 is wasm64 for clang/lld but lowered to
 // wasm32 in Binaryen (such that it can run on wasm32 engines, while internally
 // using i64 pointers).
+// Assumes WASM_BIGINT.
 // [compile+link]
 var MEMORY64 = 0;