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RISC (Reduced Instruction Set Computers, Execution Characteristic - Coggle…
RISC (Reduced Instruction Set Computers
CISC(Complex Instruction Set Computers)
Software costs far exceed hardware costs
Increasingly complex high level languages
Intention
Ease compiler writing
Improve execution efficiency
Support more complex HLLs
Why CISC?
Compiler simplification
Smaller programs
Faster programs
Compiler Based Register Optimization
Implications
optimizing most used and most time consuming features
Large Register File
Software solution
Hardware solution
Registers for Local Variables
Register Windows
Parameter registers
Temporary registers
Local registers
Circular Buffer
Global Variables
Graph Coloring
Given a graph of nodes and edges
Characteristics
One instruction per cycle
Register to register operations
Fixed instruction format
Pipelining
I: Instruction fetch
E: Execute
D: Memory
Optimization of Pipelining
Delayed branch
Optimized delayed branch
Delayed Load
Loop Unrolling
Execution Characteristic
Operations performed
Assignments
Movement of data
Conditional statements (IF, LOOP)
Sequence control
Procedure Calls
Rather narrow window of procedure-invocation depth
Operands used
Optimization should concentrate on accessing
local variables
Execution sequencing