bug 1366287 - Part 2.0: Use GMP integers to represent BigInt values. r=jwalden

Also link to libgmp and initialize it with custom memory allocation
functions.

config/system-headers.mozbuild

@@ -1339,3 +1339,8 @@ if CONFIG['MOZ_SYSTEM_ICU']:
         'unicode/ustring.h',
         'unicode/utypes.h',
     ]
+
+if CONFIG['ENABLE_BIGINT']:
+    system_headers += [
+        'gmp.h'
+    ]

js/src/build/moz.build

@@ -34,6 +34,11 @@ if CONFIG['ENABLE_INTL_API']:
         'icu',
     ]
 
+if CONFIG['ENABLE_BIGINT']:
+    OS_LIBS += [
+        'gmp',
+    ]
+
 USE_LIBS += [
     'nspr',
     'zlib',

js/src/vm/BigIntType.cpp

@@ -9,43 +9,82 @@
 #include "mozilla/FloatingPoint.h"
 #include "mozilla/HashFunctions.h"
 
+#include <gmp.h>
+#include <math.h>
+
 #include "jsapi.h"
 
 #include "gc/Allocator.h"
 #include "gc/Tracer.h"
+#include "js/Utility.h"
 #include "vm/JSContext.h"
 #include "vm/SelfHosting.h"
 
 using namespace js;
 
+// The following functions are wrappers for use with
+// mp_set_memory_functions. GMP passes extra arguments to the realloc
+// and free functions not needed by the JS allocation interface.
+// js_malloc has the signature expected for GMP's malloc function, so no
+// wrapper is required.
+
+static void*
+js_mp_realloc(void* ptr, size_t old_size, size_t new_size)
+{
+    return js_realloc(ptr, new_size);
+}
+
+static void
+js_mp_free(void* ptr, size_t size)
+{
+    return js_free(ptr);
+}
+
+void
+BigInt::init()
+{
+    mp_set_memory_functions(js_malloc, js_mp_realloc, js_mp_free);
+}
+
 BigInt*
 BigInt::create(JSContext* cx)
 {
     BigInt* x = Allocate<BigInt>(cx);
     if (!x)
         return nullptr;
+    mpz_init(x->num_); // to zero
     return x;
 }
 
 BigInt*
 BigInt::copy(JSContext* cx, HandleBigInt x)
 {
-    BigInt* bi = create(cx);
+    BigInt* bi = Allocate<BigInt>(cx);
     if (!bi)
         return nullptr;
+    mpz_init_set(bi->num_, x->num_);
     return bi;
 }
 
 JSLinearString*
 BigInt::toString(JSContext* cx, BigInt* x)
 {
-    return nullptr;
+    // We need two extra chars for '\0' and potentially '-'.
+    size_t strSize = mpz_sizeinbase(x->num_, 10) + 2;
+    UniqueChars str(static_cast<char*>(js_malloc(strSize)));
+    if (!str) {
+        ReportOutOfMemory(cx);
+        return nullptr;
+    }
+    mpz_get_str(str.get(), 10, x->num_);
+
+    return NewStringCopyZ<CanGC>(cx, str.get());
 }
 
 void
 BigInt::finalize(js::FreeOp* fop)
 {
-    return;
+    mpz_clear(num_);
 }
 
 JSAtom*
@@ -60,24 +99,35 @@ js::BigIntToAtom(JSContext* cx, BigInt* bi)
 bool
 BigInt::toBoolean()
 {
-    return false;
+    return mpz_sgn(num_) != 0;
 }
 
 js::HashNumber
 BigInt::hash()
 {
-    return 0;
+    const mp_limb_t* limbs = mpz_limbs_read(num_);
+    size_t limbCount = mpz_size(num_);
+    uint32_t hash = mozilla::HashBytes(limbs, limbCount * sizeof(mp_limb_t));
+    hash = mozilla::AddToHash(hash, mpz_sgn(num_));
+    return hash;
 }
 
 size_t
 BigInt::sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const
 {
-    return 0;
+    // Use the total number of limbs allocated when calculating the size
+    // (_mp_alloc), not the number of limbs currently in use (_mp_size).
+    // See the Info node `(gmp)Integer Internals` for details.
+    mpz_srcptr n = static_cast<mpz_srcptr>(num_);
+    return sizeof(*n) + sizeof(mp_limb_t) * n->_mp_alloc;
 }
 
 JS::ubi::Node::Size
 JS::ubi::Concrete<BigInt>::size(mozilla::MallocSizeOf mallocSizeOf) const
 {
-    MOZ_ASSERT(get().isTenured());
-    return js::gc::Arena::thingSize(get().asTenured().getAllocKind());
+    BigInt& bi = get();
+    MOZ_ASSERT(bi.isTenured());
+    size_t size = js::gc::Arena::thingSize(bi.asTenured().getAllocKind());
+    size += bi.sizeOfExcludingThis(mallocSizeOf);
+    return size;
 }

js/src/vm/BigIntType.h

@@ -7,6 +7,8 @@
 #ifndef vm_BigIntType_h
 #define vm_BigIntType_h
 
+#include <gmp.h>
+
 #include "gc/Barrier.h"
 #include "gc/GC.h"
 #include "gc/Heap.h"
@@ -23,7 +25,10 @@ class BigInt final : public js::gc::TenuredCell
   private:
     // The minimum allocation size is currently 16 bytes (see
     // SortedArenaList in gc/ArenaList.h).
-    uint8_t unused_[js::gc::MinCellSize];
+    union {
+        mpz_t num_;
+        uint8_t unused_[js::gc::MinCellSize];
+    };
 
   public:
     // Allocate and initialize a BigInt value
@@ -42,6 +47,8 @@ class BigInt final : public js::gc::TenuredCell
     static JSLinearString* toString(JSContext* cx, BigInt* x);
     bool toBoolean();
 
+    static void init();
+
     static BigInt* copy(JSContext* cx, Handle<BigInt*> x);
 };
 

js/src/vm/Initialization.cpp

@@ -25,6 +25,9 @@
 #include "unicode/uclean.h"
 #include "unicode/utypes.h"
 #endif // ENABLE_INTL_API
+#ifdef ENABLE_BIGINT
+#include "vm/BigIntType.h"
+#endif
 #include "vm/DateTime.h"
 #include "vm/HelperThreads.h"
 #include "vm/Runtime.h"
@@ -134,6 +137,10 @@ JS::detail::InitWithFailureDiagnostic(bool isDebugBuild)
     RETURN_IF_FAIL(js::jit::SimulatorProcess::initialize());
 #endif
 
+#ifdef ENABLE_BIGINT
+    JS::BigInt::init();
+#endif
+
     libraryInitState = InitState::Running;
     return nullptr;
 }