 RealView Compiler User's Guide | |
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RealView Compiler User's Guide
Preface Introduction Getting started with the ARM Compiler Compiler Features Coding Practices Diagnostic Messages Using the Inline and Embedded Assemblers Inline assembler
Inline assembler syntax Restrictions on inline assembly operations Virtual registers Constants Instruction expansion Condition flags Operands Function calls and branches Labels Differences from previous versions of the ARM C/C+ Embedded assembler Embedded assembler syntax Restrictions on embedded assembly Differences between expressions in embedded assemb Generation of embedded assembly functions The __cpp keyword Manual overload resolution Keywords for related base classes Keywords for member function classes Calling non‑static member functions Differences from previous versions of the ARM C/C+ Legacy inline assembler that accesses sp, lr, or p Accessing sp (r13), lr (r14), and pc (r15) in lega Differences between inline and embedded assembly c SemihostingDifferences between inline and embedded assembly code
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| Home > Using the Inline and Embedded Assemblers > Differences between inline and embedded assembly code | |||
There are differences between the way inline and embedded assembly is compiled:
Inline assembly code uses a high‑level of processor abstraction, and is integrated with the C and C++ code during code generation. Therefore, the compiler optimizes the C and C++ code, and the assembly code together.
Unlike inline assembly code, embedded assembly code is assembled separately from the C and C++ code to produce a compiled object that is then combined with the object from the compilation of the C or C++ source.
Inline assembly code can be inlined by the compiler, but embedded assembly code cannot be inlined, either implicitly or explicitly.
Table 6.1 summarizes the main differences between inline assembler and embedded assembler.
Table 6.1. Differences between inline and embedded assembler
| Feature | Embedded assembler | Inline assembler |
|---|---|---|
| Instruction set | ARM and Thumb. | ARM only. |
| ARM assembler directives | All supported. | None supported. |
| ARMv6 instructions | All supported. | Supports only the media instructions. |
| C/C++ expressions | Constant expressions only. | Full C/C++ expressions. |
| Optimization of assembly code | No optimization. | Full optimization. |
| Inlining | Never. | Possible. |
| Register access | Specified physical registers are used. You can also use PC, LR and SP. | Uses virtual registers (see Virtual registers). Using |
| Return instructions | You must add them in your code. | Generated automatically. (The BX , BXJ, and BLX instructions are not supported.) |
BKPT instruction | Supported directly. | Not supported. |
See also Differences between expressions in embedded assembly and C or C++.
| Copyright © 2007 ARM Limited. All rights reserved. | ARM DUI 0375A |
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