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The IBM System/360 Model 91 was an early machine that supported out-of-order execution of instructions; it used the Tomasulo algorithm, which uses register renaming. The POWER1 from 1990 is the first microprocessor that used register renaming and out-of-order execution. This processor implemented register renaming only for floating-point loads.
Tomasulo's algorithm uses register renaming to correctly perform out-of-order execution. All general-purpose and reservation station registers hold either a real value or a placeholder value. If a real value is unavailable to a destination register during the issue stage, a placeholder value is initially used.
Alpha-renaming can make static code analysis easier since only the alpha renamer needs to understand the language's scoping rules. For example, in this code: class Point { private : double x , y ; public : Point ( double x , double y ) { // x and y declared here mask the privates setX ( x ); setY ( y ); } void setX ( double newx ) { x = newx ...
F i: Destination register; F j,F k: Source-register numbers; Q j,Q k: Functional units that will produce the source registers F j, F k; R j,R k: Flags that indicates when F j, F k are ready for and are not yet read. Register Status: Indicates, for each register, which function unit will write results into it.
While process advances will allow ever greater numbers of execution units (e.g. ALUs), the burden of checking instruction dependencies grows rapidly, as does the complexity of register renaming circuitry to mitigate some dependencies. Collectively the power consumption, complexity and gate delay costs limit the achievable superscalar speedup.
A register file is an array of processor registers in a central processing unit (CPU). The instruction set architecture of a CPU will almost always define a set of registers which are used to stage data between memory and the functional units on the chip.
In the stdcall and fastcall mangling schemes, the function is encoded as _name@X and @name@X respectively, where X is the number of bytes, in decimal, of the argument(s) in the parameter list (including those passed in registers, for fastcall). In the case of cdecl, the function name is merely prefixed by an underscore.
The most common source inputs for high-level synthesis are based on standard languages such as ANSI C/C++, SystemC and MATLAB. High-level synthesis typically also includes a bit-accurate executable specification as input, since to derive an efficient hardware implementation, additional information is needed on what is an acceptable Mean-Square ...