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C51: LROL AND LROR FUNCTIONS ARE NOT INTRINSIC


Information in this article applies to:

  • C51 Version 6.20

SYMPTOMS

The manual states that the crol, irol, lrol, cror, iror, and lror functions are implemented as intrinsic routines. When I use them, however, the lrol and lror functions are not intrinsic.

CAUSE

This is correct. The crol, cror, irol, and iror functions are implemented intrinsicly (that is, the code is expanded in-line with no function calls). The lror and lrol function are not implemented intrinsicly (these routines are called). The reason for this is that on the 8051, a lror or lrol requires a number of operations (since there is no 32-bit ROL or ROR instruction). Since these routines require so many instructions, it is more efficient to implement these routines as functions instead of in-line code.

RESOLUTION

These is no way to change this behavior. The manual will be updated to reflect the correct operation of these routines.

MORE INFORMATION

  • Refer to _lrol_ in the Cx51 User's Guide.
  • Refer to _lror_ in the Cx51 User's Guide.

Last Reviewed: Tuesday, October 24, 2006


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