1 files changed, 38 insertions, 0 deletions
diff --git a/tensorflow/contrib/lite/kernels/internal/quantization_util.h b/tensorflow/contrib/lite/kernels/internal/quantization_util.h
index 9ee4a47fbb..d74a1bac97 100644
--- a/tensorflow/contrib/lite/kernels/internal/quantization_util.h
+++ b/tensorflow/contrib/lite/kernels/internal/quantization_util.h
@@ -195,6 +195,44 @@ void QuantizeMultiplierGreaterThanOne(double double_multiplier,
 void QuantizeMultiplier(double double_multiplier, int32_t* quantized_multiplier,
                         int* shift);
 
+// Splits a double input value into a returned fraction, and a shift value from
+// the exponent, using only bitwise and integer operations to support
+// microcontrollers and other environments without floating-point support.
+//
+// This is designed to be a replacement for how std::frexp() is used within the
+// QuantizeMultiplier() function, and so has a different signature than the
+// standard version, returning a 64-bit integer rather than a double. This
+// result has a maximum value of 1<<31, with the fraction expressed as a
+// proportion of that maximum.
+//
+// std::frexp() returns NaNs and infinities unmodified, but since we're
+// returning integers that can't represent those values, instead we return
+// a shift of std::numeric_limits<int>::max() for all bad numbers, with an int64
+// result of 0 for NaNs, std:numeric_limits<int64_t>::max() for +INFINITY, and
+// std::numeric_limits<int64_t>::min() for -INFINITY. Denormalized inputs will
+// result in return values that end up truncating some bits at the end,
+// reflecting the loss of precision inherent in denormalization.
+int64_t IntegerFrExp(double input, int* shift);
+
+// Converts an integer fraction in the format produced by IntegerFrExp (where
+// 0x40000000 is 1.0) and an exponent shift (between -1022 and +1022) into an
+// IEEE binary64 double format result. The implementation uses only integer and
+// bitwise operators, so no floating point hardware support or emulation is
+// needed. This is here so quantized operations can run non-time-critical
+// preparation calculations on microcontrollers and other platforms without
+// float support.
+double DoubleFromFractionAndShift(int64_t fraction, int shift);
+
+// Performs a multiplication of two numbers in double format, using only integer
+// and bitwise instructions. This is aimed at supporting housekeeping functions
+// for quantized operations on microcontrollers without floating-point hardware.
+double IntegerDoubleMultiply(double a, double b);
+
+// Returns -1 if a is less than b, 0 if a and b are equal, and +1 if a is
+// greater than b. It is implemented using only integer and logical instructions
+// so that it can be easily run on microcontrollers for quantized operations.
+int IntegerDoubleCompare(double a, double b);
+
 // This first creates a multiplier in a double equivalent of
 // Q(input_integer_bits).(31-input_integer_bits) representation, with extra
 // precision in the double's fractional bits.  It then splits the result into