IAR 编译优化 #pragma optimize

在IAR工具菜单栏中 点击 【help】-> 【Serach】 搜索optimize 

 说明：单独指定的优化等级优先级高于编译器统一指定的优化。

1、格式

#pragma optimize=[goal][level][vectorize][disable]

Parameters

goal	Choose between: size, optimizes for size balanced, optimizes balanced between speed and size speed, optimizes for speed. no_size_constraints, optimizes for speed, but relaxes the normal restrictions for code size expansion.
level	Specifies the level of optimization—choose between none, low, medium, or high.
vectorize	Enables generation of NEON vector instructions.
disable	Disables one or several optimizations (separated by spaces). Choose between: no_code_motion, disables code motion no_cse, disables common subexpression elimination no_inline, disables function inlining no_relaxed_fp, disables the language relaxation that optimizes floating-point expressions more aggressively no_tbaa, disables type-based alias analysis no_scheduling, disables instruction scheduling. no_vectorize, disables generation of NEON vector instructions no_unroll, disables loop unrolling

 2、Example

2.1、速度和空间优化

#pragma optimize=speed
int SmallAndUsedOften()
{  
/* Do something here. */
} 
#pragma optimize=size
int BigAndSeldomUsed()
{  
/* Do something here. */
}

2.2、最高速优化

如果想设置优化速度到最高等级,则如下设置即可

#pragma optimize=speed high
int SmallAndUsedOften()
{
/* Do something here. */
}

2.3、禁用优化

如果需要针对某个函数禁用所有优化

/// @brief 延时us级别 实测误差  1us > 1.192us
/// @param us 延时时间
#pragma optimize = none //防止优化
void sleep_us(uint32_t us)
{
        for (size_t i = 0; i < us; i++)
        {
                for (size_t j = 0; j < 11; j++)
                {
                }
        }
}