Re: [ANN] LuaJIT-2.0.0-beta1

[Mike Pall <mikelu-0911@...>]

Geoff Leyland wrote:
> > =math.random()
> 1.7863937924312

Ok, so Apple thinks -fpic is a good on x86. And I'm stupid because
I broke it.

Patch attached. Thank you for the report!

--Mike

--- a/src/lib_math.c
+++ b/src/lib_math.c
@@ -98,8 +98,8 @@ typedef union { uint64_t u64; double d; } U64double;
   z = (((z<<q)^z) >> (k-s)) ^ ((z&((uint64_t)(int64_t)-1 << (64-k)))<<s); \
   r ^= z; tw->gen[i] = z;
 
-/* PRNG step function. Returns a double in the range 0.0 <= d < 1.0. */
-static double tw223_step(TW223State *tw)
+/* PRNG step function. Returns a double in the range 1.0 <= d < 2.0. */
+static LJ_NOINLINE double tw223_step(TW223State *tw)
 {
   uint64_t z, r = 0;
   U64double u;
@@ -108,16 +108,7 @@ static double tw223_step(TW223State *tw)
   TW223_GEN(2, 55, 24,  7)
   TW223_GEN(3, 47, 21,  8)
   u.u64 = (r & (((uint64_t)1 << 52)-1)) | ((uint64_t)0x3ff << 52);
-#if defined(__GNUC__) && LJ_TARGET_X86 && __pic__
-  /* Compensate for unbelievable GCC pessimization. */
-  {
-    volatile U64double u1;
-    u1.u64 = (uint64_t)0x3f8 << 52;
-    return u.d - u1.d;
-  }
-#else
-  return u.d - 1.0;
-#endif
+  return u.d;
 }
 
 /* PRNG initialization function. */
@@ -146,7 +137,7 @@ LJLIB_CF(math_random)
   TW223State *tw = (TW223State *)(uddata(udataV(lj_lib_upvalue(L, 1))));
   double d;
   if (LJ_UNLIKELY(!tw->valid)) tw223_init(tw, 0.0);
-  d = tw223_step(tw);
+  d = tw223_step(tw) - 1.0;
   if (n > 0) {
     double r1 = lj_lib_checknum(L, 1);
     if (n == 1) {