Initial import

third_party/duktape/duk_tval.c

@@ -0,0 +1,152 @@
+#include "third_party/duktape/duk_internal.h"
+
+#if defined(DUK_USE_FASTINT)
+
+/*
+ *  Manually optimized double-to-fastint downgrade check.
+ *
+ *  This check has a large impact on performance, especially for fastint
+ *  slow paths, so must be changed carefully.  The code should probably be
+ *  optimized for the case where the result does not fit into a fastint,
+ *  to minimize the penalty for "slow path code" dealing with fractions etc.
+ *
+ *  At least on one tested soft float ARM platform double-to-int64 coercion
+ *  is very slow (and sometimes produces incorrect results, see self tests).
+ *  This algorithm combines a fastint compatibility check and extracting the
+ *  integer value from an IEEE double for setting the tagged fastint.  For
+ *  other platforms a more naive approach might be better.
+ *
+ *  See doc/fastint.rst for details.
+ */
+
+DUK_INTERNAL DUK_ALWAYS_INLINE void duk_tval_set_number_chkfast_fast(duk_tval *tv, duk_double_t x) {
+	duk_double_union du;
+	duk_int64_t i;
+	duk_small_int_t expt;
+	duk_small_int_t shift;
+
+	/* XXX: optimize for packed duk_tval directly? */
+
+	du.d = x;
+	i = (duk_int64_t) DUK_DBLUNION_GET_INT64(&du);
+	expt = (duk_small_int_t) ((i >> 52) & 0x07ff);
+	shift = expt - 1023;
+
+	if (shift >= 0 && shift <= 46) {  /* exponents 1023 to 1069 */
+		duk_int64_t t;
+
+		if (((DUK_I64_CONSTANT(0x000fffffffffffff) >> shift) & i) == 0) {
+			t = i | DUK_I64_CONSTANT(0x0010000000000000);  /* implicit leading one */
+			t = t & DUK_I64_CONSTANT(0x001fffffffffffff);
+			t = t >> (52 - shift);
+			if (i < 0) {
+				t = -t;
+			}
+			DUK_TVAL_SET_FASTINT(tv, t);
+			return;
+		}
+	} else if (shift == -1023) {  /* exponent 0 */
+		if (i >= 0 && (i & DUK_I64_CONSTANT(0x000fffffffffffff)) == 0) {
+			/* Note: reject negative zero. */
+			DUK_TVAL_SET_FASTINT(tv, (duk_int64_t) 0);
+			return;
+		}
+	} else if (shift == 47) {  /* exponent 1070 */
+		if (i < 0 && (i & DUK_I64_CONSTANT(0x000fffffffffffff)) == 0) {
+			DUK_TVAL_SET_FASTINT(tv, (duk_int64_t) DUK_FASTINT_MIN);
+			return;
+		}
+	}
+
+	DUK_TVAL_SET_DOUBLE(tv, x);
+	return;
+}
+
+DUK_INTERNAL DUK_NOINLINE void duk_tval_set_number_chkfast_slow(duk_tval *tv, duk_double_t x) {
+	duk_tval_set_number_chkfast_fast(tv, x);
+}
+
+/*
+ *  Manually optimized number-to-double conversion
+ */
+
+#if defined(DUK_USE_FASTINT) && defined(DUK_USE_PACKED_TVAL)
+DUK_INTERNAL DUK_ALWAYS_INLINE duk_double_t duk_tval_get_number_packed(duk_tval *tv) {
+	duk_double_union du;
+	duk_uint64_t t;
+
+	t = (duk_uint64_t) DUK_DBLUNION_GET_UINT64(tv);
+	if ((t >> 48) != DUK_TAG_FASTINT) {
+		return tv->d;
+	} else if (t & DUK_U64_CONSTANT(0x0000800000000000)) {
+		t = (duk_uint64_t) (-((duk_int64_t) t));  /* avoid unary minus on unsigned */
+		t = t & DUK_U64_CONSTANT(0x0000ffffffffffff);  /* negative */
+		t |= DUK_U64_CONSTANT(0xc330000000000000);
+		DUK_DBLUNION_SET_UINT64(&du, t);
+		return du.d + 4503599627370496.0;  /* 1 << 52 */
+	} else if (t != 0) {
+		t &= DUK_U64_CONSTANT(0x0000ffffffffffff);  /* positive */
+		t |= DUK_U64_CONSTANT(0x4330000000000000);
+		DUK_DBLUNION_SET_UINT64(&du, t);
+		return du.d - 4503599627370496.0;  /* 1 << 52 */
+	} else {
+		return 0.0;  /* zero */
+	}
+}
+#endif  /* DUK_USE_FASTINT && DUK_USE_PACKED_TVAL */
+
+#if 0  /* unused */
+#if defined(DUK_USE_FASTINT) && !defined(DUK_USE_PACKED_TVAL)
+DUK_INTERNAL DUK_ALWAYS_INLINE duk_double_t duk_tval_get_number_unpacked(duk_tval *tv) {
+	duk_double_union du;
+	duk_uint64_t t;
+
+	DUK_ASSERT(tv->t == DUK_TAG_NUMBER || tv->t == DUK_TAG_FASTINT);
+
+	if (tv->t == DUK_TAG_FASTINT) {
+		if (tv->v.fi >= 0) {
+			t = DUK_U64_CONSTANT(0x4330000000000000) | (duk_uint64_t) tv->v.fi;
+			DUK_DBLUNION_SET_UINT64(&du, t);
+			return du.d - 4503599627370496.0;  /* 1 << 52 */
+		} else {
+			t = DUK_U64_CONSTANT(0xc330000000000000) | (duk_uint64_t) (-tv->v.fi);
+			DUK_DBLUNION_SET_UINT64(&du, t);
+			return du.d + 4503599627370496.0;  /* 1 << 52 */
+		}
+	} else {
+		return tv->v.d;
+	}
+}
+#endif  /* DUK_USE_FASTINT && DUK_USE_PACKED_TVAL */
+#endif  /* 0 */
+
+#if defined(DUK_USE_FASTINT) && !defined(DUK_USE_PACKED_TVAL)
+DUK_INTERNAL DUK_ALWAYS_INLINE duk_double_t duk_tval_get_number_unpacked_fastint(duk_tval *tv) {
+	duk_double_union du;
+	duk_uint64_t t;
+
+	DUK_ASSERT(tv->t == DUK_TAG_FASTINT);
+
+	if (tv->v.fi >= 0) {
+		t = DUK_U64_CONSTANT(0x4330000000000000) | (duk_uint64_t) tv->v.fi;
+		DUK_DBLUNION_SET_UINT64(&du, t);
+		return du.d - 4503599627370496.0;  /* 1 << 52 */
+	} else {
+		t = DUK_U64_CONSTANT(0xc330000000000000) | (duk_uint64_t) (-tv->v.fi);
+		DUK_DBLUNION_SET_UINT64(&du, t);
+		return du.d + 4503599627370496.0;  /* 1 << 52 */
+	}
+}
+#endif  /* DUK_USE_FASTINT && DUK_USE_PACKED_TVAL */
+
+#endif  /* DUK_USE_FASTINT */
+
+/*
+ *  Assertion helpers.
+ */
+
+#if defined(DUK_USE_ASSERTIONS)
+DUK_INTERNAL void duk_tval_assert_valid(duk_tval *tv) {
+	DUK_ASSERT(tv != NULL);
+}
+#endif