Explicit conversions may be performed using the convert_destType(sourceType) suite of functions. These
provide a full set of type conversions between supported types (see scalarDataTypes(3clc)) except for the
following types: bool, half, size_t, ptrdiff_t, intptr_t, uintptr_t, and void.
The number of elements in the source and destination vectors must match.
The behavior of the conversion may be modified by one or two optional modifiers that specify saturation
for out-of-range inputs and rounding behavior.
The full form of the scalar convert function is:
destType
convert_destType<_sat><_roundingMode>(sourceType)
The full form of the vector convert function is:
destTypen
convert_destTypen<_sat><_roundingMode>(sourceTypen)
Conversions are available for the following scalar types: char, uchar, short, ushort, int, uint, long,
ulong, float, and built-in vector types derived therefrom. The operand and result type must have the same
number of elements. The operand and result type may be the same type in which case the conversion has no
effect on the type or value of an expression.
Conversions between integer types follow the conversion rules specified in sections 6.3.1.1 and 6.3.1.3
of the C99 specification except for out-of-range behavior and saturated conversions which are described
in section 6.2.3.3 below. Rounding Modes.PP Conversions to and from floating-point type shall conform to
IEEE-754 rounding rules. Conversions may have an optional rounding mode modifier described in the table
below.
┌──────────────────────────────┬───────────────────────────────────────┐
│ Modifier │ RoundingModeDescription │
├──────────────────────────────┼───────────────────────────────────────┤
│ │ │
│ _rte │ Round to nearest even │
├──────────────────────────────┼───────────────────────────────────────┤
│ │ │
│ _rtz │ Round towards zero │
├──────────────────────────────┼───────────────────────────────────────┤
│ │ │
│ _rtp │ Round toward positive infinity │
├──────────────────────────────┼───────────────────────────────────────┤
│ │ │
│ _rtn │ Round toward negative infinity │
├──────────────────────────────┼───────────────────────────────────────┤
│ │ │
│ no modifier specified │ Use the default rounding mode │
│ │ for this destination type, │
│ │ _rtz for conversion to │
│ │ integers or the default │
│ │ rounding mode for conversion │
│ │ to floating-point types. │
└──────────────────────────────┴───────────────────────────────────────┘
By default, conversions to integer type use the _rtz (round toward zero) rounding mode and conversions to
floating-point type use the default rounding mode. The only default floating-point rounding mode
supported is round to nearest even, i.e the default rounding mode will be _rte for floating-point types.
For conversions to floating-point format, when a finite source value exceeds the maximum representable
finite floating-point destination value, the rounding mode will affect whether the result is the maximum
finite floating point value or infinity of same sign as the source value, per IEEE-754 rules for
rounding.
Out-of-Range Behavior and Saturated Conversions
When the conversion operand is either greater than the greatest representable destination value or less
than the least representable destination value, it is said to be out-of-range. The result of out-of-range
conversion is determined by the conversion rules specified by the C99 specification in section 6.3. When
converting from a floating-point type to integer type, the behavior is implementation-defined.
Conversions to integer type may opt to convert using the optional saturated mode by appending the _sat
modifier to the conversion function name. When in saturated mode, values that are outside the
representable range shall clamp to the nearest representable value in the destination format. (NaN should
be converted to 0).
Conversions to floating-point type shall conform to IEEE-754 rounding rules. The _sat modifier may not be
used for conversions to floating-point formats.
Examples
In the following example, convert_int4 converts a uchar4 vector u to an int4 vector c:
uchar4 u; int4 c = convert_int4(u);
In the following example, convert_int converts a float scalar f to an int scalar i:
float f; int i = convert_int(f);
Example:
short4 s;
// negative values clamped to 0 ushort4 u =
convert_ushort4_sat( s );
// values > CHAR_MAX converted to CHAR_MAX // values <
CHAR_MIN converted to CHAR_MIN char4 c =
convert_char4_sat( s );
Example:
float4 f;
// values implementation defined for // f > INT_MAX, f <
INT_MIN or NaN int4 i = convert_int4( f );
// values > INT_MAX clamp to INT_MAX, values < INT_MIN
clamp // to INT_MIN. NaN should produce 0.
// The _rtz rounding mode is // used to produce the
integer values. int4 i2 = convert_int4_sat( f );
// similar to convert_int4, except that //
floating-point values are rounded to the nearest //
integer instead of truncated int4 i3 =
convert_int4_rte( f );
// similar to convert_int4_sat, except that //
floating-point values are rounded to the // nearest
integer instead of truncated int4 i4 =
convert_int4_sat_rte( f );
Example:
int4 i;
// convert ints to floats using the default rounding
mode. float4 f = convert_float4( i );
// convert ints to floats. integer values that cannot //
be exactly represented as floats should round up to the
// next representable float. float4 f =
convert_float4_rtp( i );
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