ARM Compiler toolchain v4.1 for µVision Using the Compiler
ARM Compiler toolchain v4.1 for µVision Using the Compiler
ARM Compiler toolchain v4.1 for µVision Using the Compiler
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<strong>Using</strong> <strong>the</strong> Inline and Embedded Assemblers of <strong>the</strong> <strong>ARM</strong> <strong>Compiler</strong><br />
7.51 Differences in compiler support of inline and embedded assembly code<br />
There are differences between <strong>the</strong> way inline and embedded assembly is compiled:<br />
• Inline assembly code uses a high level of processor abstraction, and is integrated with <strong>the</strong><br />
C and C++ code during code generation. There<strong>for</strong>e, <strong>the</strong> compiler optimizes <strong>the</strong> C and C++<br />
code and <strong>the</strong> assembly code toge<strong>the</strong>r.<br />
• Unlike inline assembly code, embedded assembly code is assembled separately from <strong>the</strong><br />
C and C++ code to produce a compiled object that is <strong>the</strong>n combined with <strong>the</strong> object from<br />
<strong>the</strong> compilation of <strong>the</strong> C or C++ source.<br />
• Inline assembly code can be inlined by <strong>the</strong> compiler, but embedded assembly code cannot<br />
be inlined, ei<strong>the</strong>r implicitly or explicitly.<br />
Table 7-1 summarizes <strong>the</strong> main differences between inline assembler and embedded assembler.<br />
Table 7-1 Differences between inline and embedded assembler<br />
Feature Embedded assembler Inline assembler<br />
Instruction set <strong>ARM</strong> and Thumb. <strong>ARM</strong> only.<br />
<strong>ARM</strong> assembler directives All supported. None supported.<br />
<strong>ARM</strong>v6 instructions All supported. Supports most instructions, with some<br />
exceptions, <strong>for</strong> example SETEND and<br />
some of <strong>the</strong> system extensions. The<br />
complete set of <strong>ARM</strong>v6 SIMD<br />
instructions is supported.<br />
<strong>ARM</strong>v7 instructions All supported. Not supported.<br />
C/C++ expressions Constant expressions only. Full C/C++ expressions.<br />
Optimization of assembly code No optimization. Full optimization.<br />
Inlining Never. Possible.<br />
Register access<br />
Return instructions<br />
Specified physical registers<br />
are used. You can also use<br />
PC, LR and SP.<br />
You must add <strong>the</strong>m in your<br />
code.<br />
Uses virtual registers. <strong>Using</strong> sp (r13), lr<br />
(r14), and pc (r15) gives an error.<br />
Generated automatically. (The BX, BXJ,<br />
and BLX instructions are not supported.)<br />
BKPT instruction Supported directly. Not supported.<br />
7.51.1 See also<br />
Concepts<br />
• Differences between expressions in embedded assembler and C or C++ on page 7-44<br />
• Inline assembler and register access in C and C++ code on page 7-18<br />
• Legacy inline assembler that accesses sp, lr, or pc on page 7-56<br />
• <strong>Compiler</strong> support <strong>for</strong> inline assembly language on page 7-4<br />
• <strong>Compiler</strong> support <strong>for</strong> embedded assembler on page 7-36.<br />
<strong>ARM</strong> DUI 0375C Copyright © 2007-2008, 2011 <strong>ARM</strong>. All rights reserved. 7-58<br />
ID061811<br />
Non-Confidential
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