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Fixing FloatingPointUtils.round to include the fix for #12137 #14133

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janvorli merged 1 commit into from
Sep 22, 2017
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Fixing FloatingPointUtils.round to include the fix for #12137 #14133

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28 changes: 16 additions & 12 deletions src/jit/utils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1769,13 +1769,16 @@ unsigned __int64 FloatingPointUtils::convertDoubleToUInt64(double d)

// Rounds a double-precision floating-point value to the nearest integer,
// and rounds midpoint values to the nearest even number.
// Note this should align with classlib in floatdouble.cpp
// Specializing for x86 using a x87 instruction is optional since
// this outcome is identical across targets.
double FloatingPointUtils::round(double x)
{
// ************************************************************************************
// IMPORTANT: Do not change this implementation without also updating Math.Round(double),
// MathF.Round(float), and FloatingPointUtils::round(float)
// ************************************************************************************

// If the number has no fractional part do nothing
// This shortcut is necessary to workaround precision loss in borderline cases on some platforms

if (x == (double)((INT64)x))
{
return x;
Expand All @@ -1784,10 +1787,9 @@ double FloatingPointUtils::round(double x)
// We had a number that was equally close to 2 integers.
// We need to return the even one.

double tempVal = (x + 0.5);
double flrTempVal = floor(tempVal);
double flrTempVal = floor(x + 0.5);

if ((flrTempVal == tempVal) && (fmod(tempVal, 2.0) != 0))
if ((x == (floor(x) + 0.5)) && (fmod(flrTempVal, 2.0) != 0))
{
flrTempVal -= 1.0;
}
Expand All @@ -1809,13 +1811,16 @@ double FloatingPointUtils::round(double x)

// Rounds a single-precision floating-point value to the nearest integer,
// and rounds midpoint values to the nearest even number.
// Note this should align with classlib in floatsingle.cpp
// Specializing for x86 using a x87 instruction is optional since
// this outcome is identical across targets.
float FloatingPointUtils::round(float x)
{
// ************************************************************************************
// IMPORTANT: Do not change this implementation without also updating MathF.Round(float),
// Math.Round(double), and FloatingPointUtils::round(double)
// ************************************************************************************

// If the number has no fractional part do nothing
// This shortcut is necessary to workaround precision loss in borderline cases on some platforms

if (x == (float)((INT32)x))
{
return x;
Expand All @@ -1824,10 +1829,9 @@ float FloatingPointUtils::round(float x)
// We had a number that was equally close to 2 integers.
// We need to return the even one.

float tempVal = (x + 0.5f);
float flrTempVal = floorf(tempVal);
float flrTempVal = floorf(x + 0.5f);

if ((flrTempVal == tempVal) && (fmodf(tempVal, 2.0f) != 0))
if ((x == (floorf(x) + 0.5f)) && (fmodf(flrTempVal, 2.0f) != 0))
{
flrTempVal -= 1.0f;
}
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