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Pragmas for optimization

AN3350

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Doc ID 018512 Rev 2

Pragmas for optimization

22.1

global_optimizer

Controls whether the Global Optimizer is invoked by the compiler.

Syntax

#pragma global_optimizer on | off | reset

Remarks

In most compilers, this #pragma determines whether the Global Optimizer is invoked

(configured by options in the panel of the same name). If disabled, only simple optimizations

and back-end optimizations are performed.

Note:

This is not the same as #pragma optimization_level. The Global Optimizer is invoked

even at optimization_level 0 if #pragma global_optimizer is enabled.

This pragma corresponds to the settings in the Global Optimizations panel. By default, this

setting is on.

22.2

opt_common_subs

Controls the use of common subexpression optimization.

Syntax

#pragma opt_common_subs on | off | reset

Remarks

If you enable this pragma, the compiler replaces similar redundant expressions with a single

expression. For example, if two statements in a function both use the expression

a * b * c + 10

the compiler generates object code that computes the expression only once and applies the

resulting value to both statements.

The compiler applies this optimization to its own internal representation of the object code it

produces.

This pragma does not correspond to any panel setting. By default, this settings is related to

the global_optimizer pragma.

22.3

opt_dead_assignments

Controls the use of dead store optimization.

Syntax

#pragma opt_dead_assignments on | off | reset

AN3350 데이터시트(PDF) 170 Page - STMicroelectronics