Fix displaying negative numbers in emacs

It tests for whether a number is NaN by testing whether !(x * 0 >= 0),
and this was passing for all negative numbers because -0 was considered
less than and equal to 0.

Also fix some UBsan things

Fixed #749

emu/float80-test.c

@@ -11,6 +11,8 @@
 int deconst_dummy;
 #define deconst(x) (deconst_dummy? 0 : x)
 
+#define neg(x) (x == 0 ? -1e-200/1e200 : -x)
+
 union f80 {
     float80 f;
     long double ld;
@@ -156,9 +158,9 @@ void test_math() {
     assertf(bitwise_eq(u.ld, expected) || (isnan(u.ld) && isnan(expected)) || (ua.ld == 0 && ub.ld == 0 && u.ld == 0 && expected == 0), "f80_"#op"(%.20Le, %.20Le) = %.20Le (%.20Le)", ua.ld, ub.ld, u.ld, expected)
 #define test(op, a, b) \
     _test(op, a, b); \
-    _test(op, -a, b); \
-    _test(op, a, -b); \
-    _test(op, -a, -b)
+    _test(op, neg(a), b); \
+    _test(op, a, neg(b)); \
+    _test(op, neg(a), neg(b))
 
     test(add, 1, 1);
     test(add, 123, 123);
@@ -226,20 +228,22 @@ void test_compare() {
     assertf(actual == expected, "f80_"#op"(%Le, %Le) = %s", ua.ld, ub.ld, actual ? "true" : "false")
 #define test(op, a, b) \
     _test(op, a, b); \
-    _test(op, -a, b); \
-    _test(op, a, -b); \
-    _test(op, -a, -b)
+    _test(op, neg(a), b); \
+    _test(op, a, neg(b)); \
+    _test(op, neg(a), neg(b))
 
     test(eq, 0, 0);
     test(eq, 1, 1);
     test(eq, 0, 1);
+    test(eq, 1, 0);
     test(eq, INFINITY, INFINITY);
     test(eq, 1, INFINITY);
     test(eq, NAN, 123);
     test(eq, NAN, NAN);
     test(lt, 0, 0);
     test(lt, 1, 1);
     test(lt, 0, 1);
+    test(lt, 1, 0);
     test(lt, INFINITY, INFINITY);
     test(lt, 1, INFINITY);
     test(lt, NAN, 123);

emu/float80.c

@@ -123,8 +123,10 @@ static float80 f80_normalize(float80 f) {
         return f;
     // shift left as many times as possible without overflow
     // number of leading zeroes = how many times we can shift out a leading digit before overflow
-    int shift = __builtin_clzl(f.signif);
-    if (f.signif == 0)
+    int shift;
+    if (f.signif != 0)
+        shift = __builtin_clzl(f.signif);
+    else
         shift = 64; // __builtin_clzl has undefined result with zero
     if (f.exp - shift < EXP_MIN) {
         // if we shifted this much, exponent would go below its minimum
@@ -138,10 +140,12 @@ static float80 f80_normalize(float80 f) {
 
 static int u128_clz(uint128_t x) {
     // correctly counting leading zeros on a 128-bit int is interesting
-    int zeros = __builtin_clzl((uint64_t) (x >> 64));
-    if (x >> 64 == 0)
+    int zeros;
+    if (x >> 64 != 0)
+        zeros = __builtin_clzl((uint64_t) (x >> 64));
+    else if (x != 0)
         zeros = 64 + __builtin_clzl((uint64_t) x);
-    if (x == 0)
+    else
         zeros = 128;
     return zeros;
 }
@@ -198,7 +202,7 @@ float80 f80_from_int(int64_t i) {
         f.exp = 0;
     if (i < 0) {
         f.sign = 1;
-        f.signif = -i;
+        f.signif = -(uint64_t) i;
     }
     return f80_normalize(f);
 }
@@ -460,9 +464,12 @@ float80 f80_div(float80 a, float80 b) {
         uint128_t signif = ((uint128_t) a.signif << 64) / b.signif;
         uint128_t remainder = ((uint128_t) a.signif << 64) % b.signif;
         // extend this to 128 bit precision because hell yeah
-        int extra_bits = u128_clz(signif);
-        signif <<= extra_bits;
-        signif |= (remainder << extra_bits) / b.signif;
+        int extra_bits = 0;
+        if (signif != 0) {
+            extra_bits = u128_clz(signif);
+            signif <<= extra_bits;
+            signif |= (remainder << extra_bits) / b.signif;
+        }
         int exp = unbias_denormal(a.exp) - unbias_denormal(b.exp) + 63 - b_trailing - extra_bits;
         f = u128_normalize_round(signif, exp, a.sign ^ b.sign);
     }
@@ -495,8 +502,8 @@ bool f80_lt(float80 a, float80 b) {
     if (f80_isinf(a) && f80_isinf(b) && a.sign == b.sign)
         return false;
     // zeroes are always equal
-    if (f80_iszero(a) && f80_iszero(b) && a.sign != b.sign)
-        return true;
+    if (f80_iszero(a) && f80_iszero(b))
+        return false;
     // if a < b then a - b < 0
     float80 diff = f80_sub(a, b);
     return diff.sign == 1 && !f80_iszero(diff);

fs/poll.h

@@ -65,7 +65,7 @@ struct poll_fd {
 #define POLL_HUP 16
 #define POLL_NVAL 32
 #define POLL_ONESHOT (1 << 30)
-#define POLL_EDGETRIGGERED (1 << 31)
+#define POLL_EDGETRIGGERED (1ul << 31)
 struct poll_event {
     struct fd *fd;
     int types;