Merge pull request #53 from WebAssembly/logarithmic_rep

Use logarithm of page size in intermediate representation

Author: fitzgen

interpreter/binary/decode.ml

@@ -296,7 +296,7 @@ let globaltype s =
 
 let memorytype s =
   let at, lim = limits u64 s in
-  MemoryT (at, lim, PageT 0x10000) (* TODO(custom-page-sizes) *)
+  MemoryT (at, lim, PageT 16) (* TODO(custom-page-sizes) *)
 
 let tabletype s =
   let t = reftype s in

interpreter/host/spectest.ml

@@ -28,7 +28,7 @@ let table64 =
   ExternTable (Table.alloc tt (NullRef FuncHT))
 
 let memory =
-  let mt = MemoryT (I32AT, {min = 1L; max = Some 2L}, PageT 0x10000) in
+  let mt = MemoryT (I32AT, {min = 1L; max = Some 2L}, PageT 16) in
   ExternMemory (Memory.alloc mt)
 
 let func f ts1 ts2 =

interpreter/runtime/memory.ml

@@ -17,8 +17,6 @@ exception SizeOverflow
 exception SizeLimit
 exception OutOfMemory
 
-let page_size = 0x10000L (* 64 KiB *)
-
 let valid_limits {min; max} =
   match max with
   | None -> true
@@ -31,7 +29,7 @@ let valid_size at i =
 
 let create n (PageT ps) =
   try
-    let size = Int64.(mul n (Int64.of_int ps)) in
+    let size = Int64.(shift_left n ps) in
     let mem = Array1_64.create Int8_unsigned C_layout size in
     Array1.fill mem 0;
     mem
@@ -47,7 +45,7 @@ let bound mem =
   Array1_64.dim mem.content
 
 let pagesize mem =
-  let MemoryT (_, _, PageT x) = mem.ty in Int64.of_int x
+  let MemoryT (_, _, PageT x) = mem.ty in (Int64.shift_left 1L x)
 
 let size mem =
   Int64.(div (bound mem) (pagesize mem))

interpreter/runtime/memory.mli

@@ -14,8 +14,6 @@ exception SizeOverflow
 exception SizeLimit
 exception OutOfMemory
 
-val page_size : int64
-
 val alloc : memorytype -> memory (* raises Type, SizeOverflow, OutOfMemory *)
 val type_of : memory -> memorytype
 val addrtype_of : memory -> addrtype

interpreter/text/parser.mly

@@ -466,7 +466,7 @@ tabletype :
   | addrtype limits reftype { fun c -> TableT ($1, $2, $3 c) }
 
 memorytype :
-  | addrtype limits { fun c -> MemoryT ($1, $2, PageT 0x10000) }
+  | addrtype limits { fun c -> MemoryT ($1, $2, PageT 16) }
 
 limits :
   | NAT { {min = nat64 $1 $loc($1); max = None} }
@@ -1130,7 +1130,7 @@ memory_fields :
     { fun c x loc ->
       let size = Int64.(div (add (of_int (String.length $4)) 65535L) 65536L) in
       let offset = [at_const $1 (0L @@ loc) @@ loc] @@ loc in
-      [Memory (MemoryT ($1, {min = size; max = Some size}, PageT 0x10000)) @@ loc],
+      [Memory (MemoryT ($1, {min = size; max = Some size}, PageT 16)) @@ loc],
       [Data ($4, Active (x, offset) @@ loc) @@ loc],
       [], [] }
 

interpreter/valid/valid.ml

@@ -105,7 +105,7 @@ let check_limits {min; max} range at msg =
       "size minimum must not be greater than maximum"
 
 let check_pagetype (PageT ps) at =
-  require (ps = 0x10000 || ps = 1) at "page size must be 1 or 64KiB"
+  require (ps = 16 || ps = 0) at "page size must be 1 or 64KiB"
 
 let check_numtype (c : context) (t : numtype) at =
   ()