IPR-NIOS Altera, IPR-NIOS Datasheet - Page 29

• Manufacturer Part Number: IPR-NIOS
• Description: IP NIOS II MEGACORE RENEW
• Manufacturer: Altera
• Type: MegaCorer

Specifications of IPR-NIOS

• License: Renewal License
• Lead Free Status / RoHS Status: Not applicable / Not applicable

Chapter 2: Processor Architecture
Arithmetic Logic Unit
December 2010 Altera Corporation
1
All the floating-point custom instructions are single-precision operations.
Double-precision floating-point operations are implemented in software.
When the floating-point custom instructions are not present, the Nios II compiler
treats floating-point constants as double-precision values. However, with the
floating-point custom instructions, the Nios II compiler treats floating-point constants
as single-precision numbers by default. This allows all floating-point expressions to
be evaluated in hardware, at a possible cost in precision.
If you do not wish floating-point constants to be cast down to single precision values,
append L to each constant value, to instruct the compiler to treat the constant as a
double-precision floating-point value. In this case, if an expression contains a
floating-point constant, each term in the expression is cast to double precision. As a
result, the expression is computed with software-implemented double-precision
arithmetic, at a possible cost in computation speed.
Table 2–3
computation is implemented.
Table 2–3. Floating-Point Constant Examples
With the GCC 4 compiler toolchain, precompiled libraries are compiled with
double-precision floating-point constants. The behavior of precompiled floating-point
library functions such as sin() and cos() is unaffected by the presence of the
floating-point custom instructions.
b = a × 4.67
b = a × 4.67f
b = a × 4.67L
b = a × 4.67
b = a × 4.67f
b = a × 4.67L
Example Code
shows code examples using floating-point constants, indicating how each
Custom Instructions
Floating-Point
Present?
Yes
Yes
Yes
No
No
No
Precision
Double
Double
Double
Single
Single
Single
Nios II Processor Reference Handbook
Implementation
Hardware
Hardware
Software
Software
Software
Software
2–7