ARM Compiler toolchain v4.1 for µVision Using the Compiler

Using the Inline and Embedded Assemblers of the ARM Compiler
7.19 Inline assembler effect on processor condition flags in C and C++ code
An inline assembly language instruction might explicitly or implicitly attempt to update the
processor condition flags. Inline assembly language instructions that involve only virtual
register operands or simple expression operands have predictable behavior. The condition flags
are set by the instruction if either an implicit or an explicit update is specified. The condition
flags are unchanged if no update is specified. If any of the instruction operands are not simple
operands, then the condition flags might be corrupted unless the instruction updates them. In
general, the compiler cannot easily diagnose potential corruption of the condition flags.
However, for operands that require the construction and subsequent destruction of C++
temporaries the compiler gives a warning if the instruction attempts to update the condition
flags. This is because the destruction might corrupt the condition flags.
7.19.1 See also
Concepts
• Inline assembler expression operands in C and C++ code on page 7-26
• Inline assembler operands in C and C++ code on page 7-25
• Compiler support for inline assembly language on page 7-4.
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