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Macros
Compiler Specific Definitions
Common Utility Headers - LUFA/Drivers/Common/Common.h

Compiler specific definitions for code optimization and correctness. More...

## Macros
#define | GCC_FORCE_POINTER_ACCESS(StructPtr) __asm__ __volatile__("" : "=b" (StructPtr) : "0" (StructPtr))
#define | GCC_IS_COMPILE_CONST(x) __builtin_constant_p(x)
#define | GCC_MEMORY_BARRIER()

## Detailed Description

Compiler specific definitions to expose certain compiler features which may increase the level of code optimization for a specific compiler, or correct certain issues that may be present such as memory barriers for use in conjunction with atomic variable access.

Where possible, on alternative compilers, these macros will either have no effect, or default to returning a sane value so that they can be used in existing code without the need for extra compiler checks in the user application code.

## Macro Definition Documentation

#define GCC_FORCE_POINTER_ACCESS | ( |  | StructPtr | ) | __asm__ __volatile__("" : "=b" (StructPtr) : "0" (StructPtr))

Forces GCC to use pointer indirection (via the device's pointer register pairs) when accessing the given struct pointer. In some cases GCC will emit non-optimal assembly code when accessing a structure through a pointer, resulting in a larger binary. When this macro is used on a (non `const`) structure pointer before use, it will force GCC to use pointer indirection on the elements rather than direct store and load instructions.

Parameters

  [in,out] | StructPtr | Pointer to a structure which is to be forced into indirect access mode.

#define GCC_IS_COMPILE_CONST | ( |  | x | ) | __builtin_constant_p(x)

Determines if the specified value can be determined at compile-time to be a constant value when compiling under GCC.

Parameters

  [in] | x | Value to check compile-time constantness of.

Returns
  Boolean `true` if the given value is known to be a compile time constant, `false` otherwise.

#define GCC_MEMORY_BARRIER | ( |  | ) |

Forces GCC to create a memory barrier, ensuring that memory accesses are not reordered past the barrier point. This can be used before ordering-critical operations, to ensure that the compiler does not re-order the resulting assembly output in an unexpected manner on sections of code that are ordering-specific.