Fix issues revealed by ECMAScript test262

Cosmopolitan's QuickJS is now equally conformant and performant, with
the exception of Atomics, which have been disabled since Cosmopolitan
currently doesn't support pthreads.

QuickJS memory usage -- BigNum 2021-03-27 version, 64-bit, malloc limit: -1

NAME                    COUNT     SIZE
memory allocated          937   131764  (140.6 per block)
memory used               938   116103  (8 overhead, 16.7 average slack)
atoms                     513    21408  (41.7 per atom)
objects                   170    12279  (72.2 per object)
  properties              864    15531  (5.1 per object)
  shapes                   58    12995  (224.1 per shape)
bytecode functions         13     1512
  bytecode                 13      867  (66.7 per function)
C functions                99
arrays                      1
  fast arrays               1
  elements                  1       16  (1.0 per fast array)

Result: 35/74740 errors, 1279 excluded, 485 skipped, 19 new, 2 fixed

real    2m40.828s
user    2m29.764s
sys     0m10.939s

libc/tinymath/atanh.c

@@ -22,5 +22,5 @@
  * Returns inverse hyperbolic tangent of 𝑥.
  */
 double atanh(double x) {
-  return log((1 + x) / (1 - x)) / 2;
+  return x ? log((1 + x) / (1 - x)) / 2 : x;
 }

libc/tinymath/atanhf.c

@@ -22,5 +22,5 @@
  * Returns inverse hyperbolic tangent of 𝑥.
  */
 float atanhf(float x) {
-  return logf((1 + x) / (1 - x)) / 2;
+  return x ? logf((1 + x) / (1 - x)) / 2 : x;
 }

libc/tinymath/atanhl.c

@@ -22,5 +22,5 @@
  * Returns inverse hyperbolic tangent of 𝑥.
  */
 long double atanhl(long double x) {
-  return logl((1 + x) / (1 - x)) / 2;
+  return x ? logl((1 + x) / (1 - x)) / 2 : x;
 }

libc/tinymath/expm1l.S

@@ -19,7 +19,7 @@
 #include "libc/runtime/pc.internal.h"
 #include "libc/macros.internal.h"
 
-//	Returns 𝑒^x-1.
+//	Returns 𝑒^𝑥-𝟷.
 //
 //	@param	𝑥 is an 80-bit long double passed on stack in 16-bytes
 //	@return	result of exponentiation on FPU stack in %st
@@ -27,11 +27,13 @@ expm1l:	push	%rbp
 	mov	%rsp,%rbp
 	.profilable
 	fldt	16(%rbp)
-	fxam					# isinf(x)
+	fxam
 	fstsw	%ax
 	mov	%ah,%al
-	and	$0x45,%ah
-	cmp	$5,%ah
+	and	$(FPU_C3|FPU_C2|FPU_C0)>>8,%ah
+	cmp	$(FPU_C3)>>8,%ah		# !x
+	je	0f
+	cmp	$(FPU_C2|FPU_C0)>>8,%ah		# isinf(x)
 	je	1f
 	fldl2e
 	fmulp	%st,%st(1)
@@ -50,7 +52,7 @@ expm1l:	push	%rbp
 	faddp	%st,%st(1)
 0:	pop	%rbp
 	ret
-1:	test	$2,%al				# signbit(x)
+1:	test	$FPU_C1>>8,%al			# signbit(x)
 	jz	0b
 	fstp	%st
 	fld1

libc/tinymath/powl.c

@@ -46,7 +46,11 @@ long double powl(long double x, long double y) {
             return 1;
           }
         } else if (y > 0) {
-          return y == 1 ? x : 0;
+          if (signbit(x) && y == truncl(y) && ((int64_t)y & 1)) {
+            return -0.;
+          } else {
+            return 0;
+          }
         } else if (!y) {
           return 1;
         } else {

libc/tinymath/sinh.c

@@ -22,5 +22,6 @@
  * Returns hyperbolic sine of 𝑥.
  */
 double sinh(double x) {
+  if (!x) return x;
   return (exp(x) - exp(-x)) / 2;
 }

libc/tinymath/sinhf.c

@@ -22,5 +22,6 @@
  * Returns hyperbolic sine of 𝑥.
  */
 float sinhf(float x) {
+  if (!x) return x;
   return (expf(x) - expf(-x)) / 2;
 }

libc/tinymath/sinhl.c

@@ -22,5 +22,6 @@
  * Returns hyperbolic sine of 𝑥.
  */
 long double sinhl(long double x) {
+  if (!x) return x;
   return (expl(x) - expl(-x)) / 2;
 }

libc/tinymath/tanh.c

@@ -22,6 +22,7 @@
  * Returns hyperbolic tangent of 𝑥.
  */
 double tanh(double x) {
+  if (!x) return x;
   if (isinf(x)) return copysign(1, x);
   return sinh(x) / cosh(x);
 }

libc/tinymath/tanhf.c

@@ -22,6 +22,7 @@
  * Returns hyperbolic tangent of 𝑥.
  */
 float tanhf(float x) {
+  if (!x) return x;
   if (isinf(x)) return copysignf(1, x);
   return sinhf(x) / coshf(x);
 }

libc/tinymath/tanhl.c

@@ -22,6 +22,7 @@
  * Returns hyperbolic tangent of 𝑥.
  */
 long double tanhl(long double x) {
+  if (!x) return x;
   if (isinf(x)) return copysignl(1, x);
   return sinhl(x) / coshl(x);
 }