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Compiler User Guide
Preface
Overview of the Compiler
Getting Started with the Compiler
Compiler Features
Compiler Coding Practices
Compiler Diagnostic Messages
Using the Inline and Embedded Assemblers of the AR
Compiler support for inline assembly language
Inline assembler support in the compiler
Restrictions on inline assembler support in the co
Inline assembly language syntax with the __asm key
Inline assembly language syntax with the asm keywo
Inline assembler rules for compiler keywords __asm
Restrictions on inline assembly operations in C an
Inline assembler register restrictions in C and C+
Inline assembler processor mode restrictions in C
Inline assembler Thumb instruction set restriction
Inline assembler Vector Floating-Point (VFP) restr
Inline assembler instruction restrictions in C and
Miscellaneous inline assembler restrictions in C a
Inline assembler and register access in C and C++
Inline assembler and the # constant expression spe
Inline assembler and instruction expansion in C an
Expansion of inline assembler instructions that us
Expansion of inline assembler load and store instr
Inline assembler effect on processor condition fla
Inline assembler expression operands in C and C++
Inline assembler register list operands in C and C
Inline assembler intermediate operands in C and C+
Inline assembler function calls and branches in C
Inline assembler branches and labels in C and C++
Inline assembler and virtual registers
Embedded assembler support in the compiler
Embedded assembler syntax in C and C++
Effect of compiler ARM and Thumb states on embedde
Restrictions on embedded assembly language functio
Compiler generation of embedded assembly language
Access to C and C++ compile-time constant expressi
Differences between expressions in embedded assemb
Manual overload resolution in embedded assembler
__offsetof_base keyword for related base classes i
Compiler-supported keywords for calling class memb
__mcall_is_virtual(D, f)
__mcall_is_in_vbase(D, f)
__mcall_offsetof_vbase(D, f)
__mcall_this_offset(D, f)
__vcall_offsetof_vfunc(D, f)
Calling nonstatic member functions in embedded ass
Calling a nonvirtual member function
Calling a virtual member function
Accessing sp (r13), lr (r14), and pc (r15)
Differences in compiler support for inline and emb
Compiler Command-line Options
Language Extensions
Compiler-specific Features
C and C++ Implementation Details
What is Semihosting?
Via File Syntax
Summary Table of GNU Language Extensions
Standard C Implementation Definition
Standard C++ Implementation Definition
C and C++ Compiler Implementation Limits
Expansion of inline assembler instructions that use constants
| Non-Confidential |  PDF version | ARM DUI0375H | ||
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| Home > Using the Inline and Embedded Assemblers of the ARM Compiler > Expansion of inline assembler instructions that use constants | ||||
6.17 Expansion of inline assembler instructions that use constants
A constant operand specified in an instruction is not limited to the values permitted by the instruction. Instead, the compiler might translate the instruction into a sequence of instructions with the same effect.
For example:
ADD r0,r0,#1023
might be translated into:
ADD r0,r0,#1024 SUB r0,r0,#1
Another example of expansion possibility is:
MOV rn,0x12345678
With the exception of coprocessor instructions, all ARM instructions with a constant
operand support instruction expansion. In addition, the
MUL instruction can
be expanded into a sequence of adds and shifts when the third operand is a constant.The effect of updating the
CPSR by an expanded instruction is:- Arithmetic instructions set the NZCV flags correctly.
- Logical instructions:
- Set the NZ flags correctly.
- Do not change the V flag.
- Corrupt the C flag.
Related concepts
| Non-Confidential | PDF version | ARM DUI0375H |
| Copyright © 2007, 2008, 2011, 2012, 2014-2016 ARM. All rights reserved. |
| Home > Using the Inline and Embedded Assemblers of the ARM Compiler > Expansion of inline assembler instructions that use constants |
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