assert(getActiveBits() <= 64 && "Too many bits for int64_t");
return int64_t(pVal[0]);
}
+
+ /// This method determines how many bits are required to hold the APInt
+ /// equivalent of the string given by \p str of length \p slen.
+ /// @brief Get bits required for string value.
+ static uint32_t getBitsNeeded(const char* str, uint32_t slen, uint8_t radix);
+
/// countLeadingZeros - This function is an APInt version of the
/// countLeadingZeros_{32,64} functions in MathExtras.h. It counts the number
/// of zeros from the most significant bit to the first one bit.
return *this;
}
+uint32_t APInt::getBitsNeeded(const char* str, uint32_t slen, uint8_t radix) {
+ assert(str != 0 && "Invalid value string");
+ assert(slen > 0 && "Invalid string length");
+
+ // Each computation below needs to know if its negative
+ uint32_t isNegative = str[0] == '-';
+ if (isNegative) {
+ slen--;
+ str++;
+ }
+ // For radixes of power-of-two values, the bits required is accurately and
+ // easily computed
+ if (radix == 2)
+ return slen + isNegative;
+ if (radix == 8)
+ return slen * 3 + isNegative;
+ if (radix == 16)
+ return slen * 4 + isNegative;
+
+ // Otherwise it must be radix == 10, the hard case
+ assert(radix == 10 && "Invalid radix");
+
+ // This is grossly inefficient but accurate. We could probably do something
+ // with a computation of roughly slen*64/20 and then adjust by the value of
+ // the first few digits. But, I'm not sure how accurate that could be.
+
+ // Compute a sufficient number of bits that is always large enough but might
+ // be too large. This avoids the assertion in the constructor.
+ uint32_t sufficient = slen*64/18;
+
+ // Convert to the actual binary value.
+ APInt tmp(sufficient, str, slen, radix);
+
+ // Compute how many bits are required.
+ return isNegative + tmp.logBase2();
+}
+
uint64_t APInt::getHashValue() const {
// Put the bit width into the low order bits.
uint64_t hash = BitWidth;