Fix pow() optimization inconsistencies.

1 files changed, 45 insertions, 37 deletions

diff --git a/src/lj_vmmath.c b/src/lj_vmmath.c
index 536199d8..fa0de922 100644
--- a/src/lj_vmmath.c
+++ b/src/lj_vmmath.c
@@ -30,11 +30,51 @@ LJ_FUNCA double lj_wrap_sinh(double x) { return sinh(x); }
 LJ_FUNCA double lj_wrap_cosh(double x) { return cosh(x); }
 LJ_FUNCA double lj_wrap_tanh(double x) { return tanh(x); }
 LJ_FUNCA double lj_wrap_atan2(double x, double y) { return atan2(x, y); }
-LJ_FUNCA double lj_wrap_pow(double x, double y) { return pow(x, y); }
 LJ_FUNCA double lj_wrap_fmod(double x, double y) { return fmod(x, y); }
 #endif
 
-/* -- Helper functions for generated machine code ------------------------- */
+/* -- Helper functions ---------------------------------------------------- */
+
+/* Unsigned x^k. */
+static double lj_vm_powui(double x, uint32_t k)
+{
+  double y;
+  lj_assertX(k != 0, "pow with zero exponent");
+  for (; (k & 1) == 0; k >>= 1) x *= x;
+  y = x;
+  if ((k >>= 1) != 0) {
+    for (;;) {
+      x *= x;
+      if (k == 1) break;
+      if (k & 1) y *= x;
+      k >>= 1;
+    }
+    y *= x;
+  }
+  return y;
+}
+
+/* Signed x^k. */
+double lj_vm_powi(double x, int32_t k)
+{
+  if (k > 1)
+    return lj_vm_powui(x, (uint32_t)k);
+  else if (k == 1)
+    return x;
+  else if (k == 0)
+    return 1.0;
+  else
+    return 1.0 / lj_vm_powui(x, (uint32_t)-k);
+}
+
+double lj_vm_pow(double x, double y)
+{
+  int32_t k = lj_num2int(y);
+  if ((k >= -65536 && k <= 65536) && y == (double)k)
+    return lj_vm_powi(x, k);
+  else
+    return pow(x, y);
+}
 
 double lj_vm_foldarith(double x, double y, int op)
 {
@@ -44,7 +84,7 @@ double lj_vm_foldarith(double x, double y, int op)
   case IR_MUL - IR_ADD: return x*y; break;
   case IR_DIV - IR_ADD: return x/y; break;
   case IR_MOD - IR_ADD: return x-lj_vm_floor(x/y)*y; break;
-  case IR_POW - IR_ADD: return pow(x, y); break;
+  case IR_POW - IR_ADD: return lj_vm_pow(x, y); break;
   case IR_NEG - IR_ADD: return -x; break;
   case IR_ABS - IR_ADD: return fabs(x); break;
 #if LJ_HASJIT
@@ -56,6 +96,8 @@ double lj_vm_foldarith(double x, double y, int op)
   }
 }
 
+/* -- Helper functions for generated machine code ------------------------- */
+
 #if (LJ_HASJIT && !(LJ_TARGET_ARM || LJ_TARGET_ARM64 || LJ_TARGET_PPC)) || LJ_TARGET_MIPS
 int32_t LJ_FASTCALL lj_vm_modi(int32_t a, int32_t b)
 {
@@ -80,40 +122,6 @@ double lj_vm_log2(double a)
 }
 #endif
 
-#if !LJ_TARGET_X86ORX64
-/* Unsigned x^k. */
-static double lj_vm_powui(double x, uint32_t k)
-{
-  double y;
-  lj_assertX(k != 0, "pow with zero exponent");
-  for (; (k & 1) == 0; k >>= 1) x *= x;
-  y = x;
-  if ((k >>= 1) != 0) {
-    for (;;) {
-      x *= x;
-      if (k == 1) break;
-      if (k & 1) y *= x;
-      k >>= 1;
-    }
-    y *= x;
-  }
-  return y;
-}
-
-/* Signed x^k. */
-double lj_vm_powi(double x, int32_t k)
-{
-  if (k > 1)
-    return lj_vm_powui(x, (uint32_t)k);
-  else if (k == 1)
-    return x;
-  else if (k == 0)
-    return 1.0;
-  else
-    return 1.0 / lj_vm_powui(x, (uint32_t)-k);
-}
-#endif
-
 /* Computes fpm(x) for extended math functions. */
 double lj_vm_foldfpm(double x, int fpm)
 {