implement pow64_overflow, lose the macro

Author: MichaelChirico

src/integer64.c

@@ -366,10 +366,11 @@ SEXP power_integer64_integer64(SEXP e1_, SEXP e2_, SEXP ret_){
   long long * e1 = (long long *) REAL(e1_);
   long long * e2 = (long long *) REAL(e2_);
   long long * ret = (long long *) REAL(ret_);
-  long long base, exp;
   Rboolean naflag = FALSE;
     mod_iterate(n1, n2, i1, i2) {
-        POW64(e1[i1],e2[i2],ret[i],naflag,base,exp)
+      if (pow64_overflow(e1[i1], e2[i2], &ret[i])) {
+        naflag = TRUE;
+      }
     }
     if (naflag)warning(INTEGER64_OVERFLOW_WARNING);
   return ret_;

src/integer64.h

@@ -118,6 +118,52 @@ static inline bool mul64_overflow(long long a, long long b, long long *res) {
 #endif
 }
 
+static inline bool pow64_overflow(long long base, long long exp, long long *res) {
+  // special cases: n^0, 1^m, 0^m, -1^m, n^-m, NA^m, n^NA
+  if (exp == 0) {
+    *res = 1;
+    return false;
+  }
+  if (base == 1) {
+    *res = 1;
+    return false;
+  }
+  if (base == 0) {
+    if (exp < 0) {
+      *res = NA_INTEGER64;
+      return true;
+    }
+    *res = 0;
+    return false;
+  }
+  if (base == -1) {
+    *res = exp & 1 ? -1 : 1;
+    return false;
+  }
+  if (exp < 0) {
+    *res = 0;
+    return false;
+  }
+  if (base == NA_INTEGER64 || exp == NA_INTEGER64) {
+    *res = NA_INTEGER64;
+    return false;
+  }
+  long long r = 1;
+  while (exp > 0) {
+    if (exp & 1 && mul64_overflow(r, base, &r)) {
+      *res = NA_INTEGER64;
+      return true;
+    }
+    exp >>= 1;
+    if (exp > 0 && mul64_overflow(base, base, &base)) {
+      *res = NA_INTEGER64;
+      return true;
+    }
+  }
+  *res = r;
+  return false;
+}
+
 #define PLUS64(e1,e2,ret,naflag) \
     if (e1 == NA_INTEGER64 || e2 == NA_INTEGER64) \
         ret = NA_INTEGER64; \
@@ -154,26 +200,6 @@ static inline bool mul64_overflow(long long a, long long b, long long *res) {
           ret = llroundl(longret); \
     }
 
-#define POW64(e1,e2,ret,naflag,base,exp) \
-    if (e1 == NA_INTEGER64 || e2 == NA_INTEGER64) \
-        ret = NA_INTEGER64; \
-    else if (e2 >= 0 || e1 == 1 || e1 == -1) { \
-        ret = 1; \
-        base = e1; \
-        exp = e2; \
-        while (exp > 0) { \
-            if (exp % 2 == 1) { \
-                if (mul64_overflow(ret, base, &ret)) { \
-                    ret = NA_INTEGER64; \
-                    naflag = TRUE; \
-                    break; \
-                } \
-            } \
-            base *= base; \
-            exp >>= 1; \
-        } \
-    }
-
 #define POW64REAL(e1,e2,ret,naflag,longret) \
     if (e1 == NA_INTEGER64 || ISNAN(e2)) \
         ret = NA_INTEGER64; \