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Intermediate Code Optimization involves transforming intermediate code to improve performance and remove unnecessary instructions without changing the output of the program. Example: Eliminating common sub-expressions.

Common Subexpression Elimination is an optimization that searches for instances of identical expressions and replaces them with a single variable holding the computed value. Example: Computing 'a*b' once and reusing it.

Constant folding is an optimization that evaluates constant expressions at compile-time instead of at runtime. Example: Replacing '3+2' with '5' during compilation.

Triples are similar to quadruples but do not include an explicit result field. The result is implicitly stored in a temporary variable that can be referred to by its position. Example: (+, y, z) represents t1 = y + z, where t1 is the temporary variable.

Intermediate Representation is a data structure or code used by a compiler to represent source code. It is a bridge between the source and the machine code. Examples include Three-Address Code, Quadruples, and ASTs.

Type checking is the process of verifying and enforcing the constraints of types in intermediate code. It ensures that operations are performed on compatible types. Example: Ensuring addition is performed between numbers.

Dead code elimination is a compiler optimization that removes code which does not affect the program results (e.g., instructions after a return statement, or assigning values to never-used variables).

An Abstract Syntax Tree is a tree representation of the abstract syntactic structure of source code. Nodes in an AST represent constructs in the language (e.g., expressions, statements).

A Control Flow Graph is a graphical representation of all paths that might be traversed through a program during execution. It represents the order in which different blocks of instructions execute.

A basic block is a sequence of consecutive statements in which flow of control enters at the beginning and leaves at the end without halt or possibility of branching except at the end.

Peephole Optimization is a technique that makes a pass over a segment of intermediate code and optimizes small sets of instructions (the 'peephole'). Example: Replacing 'x = y * 1' with 'x = y'.

Code motion is an optimization that moves statements out of loops, if the values computed are the same for each loop iteration, to reduce the total number of computations. Example: Moving invariants outside the loop.

A Directed Acyclic Graph is used to represent expressions that share common sub-expressions. In a DAG, each node represents a unique sub-expression. Example: Nodes for a + b and a + b + c would share the a + b node.

Static Single Assignment is a property of an intermediate representation, which requires that every variable is assigned exactly once. Each use of a variable is replaced by one of its assignments. Example: x1 = y + z, x2 = x1 - w

Strength reduction is a technique of replacing a costly operation with a less costly one. Example: Replacing an integer multiplication with addition (e.g., 'x * 2' becomes 'x + x').

A symbol table is a data structure used by a compiler to keep track of semantics of variables (e.g., type information, scope level, memory location). Each identifier in a program is associated with its record in the symbol table.

Loop unrolling is an optimization that increases a program's performance by decreasing the number of instructions executed for loop control, typically by executing the loop body multiple times per iteration. Example: Duplicating the loop body to reduce iterations.

Quadruples are a way to represent three-address code, where each instruction is divided into four fields: operator, arg1, arg2, result. Example: (+, y, z, x) represents x = y + z.

Three-address code is an intermediate code used by compilers to represent a program. In this form, each instruction consists of at most three addresses or operands. Example: x = y + z