Merge branch 'lukas/erts/large_float_cmp/OTP-9497'

* lukas/erts/large_float_cmp/OTP-9497:
  Update documentation after changes in integer and float comparison
  Do small optimisation on platforms with 32 bit Eterm
  Add tests for equality checking
  Optimize comparison of huge floats and smaller bignums
  Add tests for comparing large floats and small bignums
  Cleanup double_to_bignum conversion code
  Update size of tmp cmp bignum buffer
  Expand tests for float and number comparison
  Update heauristic to work on halfword
  Add heauristics bignum vs float checks
  Optimise bugnum and small comparison
  Add float vs integer comparison tests
  Update integer and floating point number comparisons

1 files changed, 56 insertions, 0 deletions

diff --git a/erts/emulator/beam/big.c b/erts/emulator/beam/big.c
index d18de9ae5d..b90ea6b478 100644
--- a/erts/emulator/beam/big.c
+++ b/erts/emulator/beam/big.c
@@ -1584,6 +1584,62 @@ big_to_double(Wterm x, double* resp)
     return 0;
 }
 
+/*
+ * Logic has been copied from erl_bif_guard.c and slightly
+ * modified to use a static instead of dynamic heap
+ */
+Eterm
+double_to_big(double x, Eterm *heap)
+{
+    int is_negative;
+    int ds;
+    ErtsDigit* xp;
+    Eterm res;
+    int i;
+    size_t sz;
+    Eterm* hp;
+    double dbase;
+
+    if (x >= 0) {
+	is_negative = 0;
+    } else {
+	is_negative = 1;
+	x = -x;
+    }
+
+    /* Unscale & (calculate exponent) */
+    ds = 0;
+    dbase = ((double) (D_MASK) + 1);
+    while (x >= 1.0) {
+	x /= dbase; /* "shift" right */
+	ds++;
+    }
+    sz = BIG_NEED_SIZE(ds); /* number of words including arity */
+
+    hp = heap;
+    res = make_big(hp);
+    xp = (ErtsDigit*) (hp + 1);
+
+    for (i = ds - 1; i >= 0; i--) {
+	ErtsDigit d;
+
+	x *= dbase; /* "shift" left */
+	d = x; /* trunc */
+	xp[i] = d; /* store digit */
+	x -= d; /* remove integer part */
+    }
+    while ((ds & (BIG_DIGITS_PER_WORD - 1)) != 0) {
+	xp[ds++] = 0;
+    }
+
+    if (is_negative) {
+	*hp = make_neg_bignum_header(sz-1);
+    } else {
+	*hp = make_pos_bignum_header(sz-1);
+    }
+    return res;
+}
+
 
 /*
  ** Estimate the number of decimal digits (include sign)