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Migration and Compatibility Guide
Preface
Configuration and Support Information
Migrating from Arm Compiler 5 to Arm Compiler 6
Migrating from armcc to armclang
Compiler Source Code Compatibility
Migrating from armasm to the armclang Integrated A
Migration of assembler command-line options from a
Overview of differences between armasm and GNU syn
Comments
Labels
Numeric local labels
Functions
Sections
Symbol naming rules
Numeric literals
Operators
Alignment
PC-relative addressing
A32 and T32 instruction substitutions
A32 and T32 pseudo-instructions
Conditional directives
Data definition directives
Instruction set directives
Miscellaneous directives
Symbol definition directives
Migration of armasm macros to integrated assembler
Changes Between Different Versions of Arm Compiler
Code Examples
Licenses
Arm Compiler Migration and Compatibility Guide Cha
Alignment
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5.11 Alignment
Data and code must be aligned to appropriate boundaries.
For example, The T32 pseudo-instruction ADR
can only load addresses that are word aligned, but a label within T32 code might not be word aligned. You must use an alignment directive to ensure four-byte alignment of an address within T32 code.
An alignment directive aligns the current location to a specified boundary by padding with zeros or
NOP instructions.
armasm syntax
armasm syntax assembly provides the ALIGN directive, where nnALIGN 128 aligns addresses to 128-byte boundaries.
armasm syntax assembly also provides the PRESERVE8 directive. The PRESERVE8 directive specifies that the current file preserves
eight-byte alignment of the stack.
GNU syntax
GNU syntax assembly provides the .balign directive, which uses the same format as nALIGN.
Convert all instances of ALIGN to n.balign .n
Note:
GNU syntax assembly also provides the.align
n directive. However, the format
of n.balign directive provides
the same alignment functionality as .align with a
consistent behavior across all architectures.Convert all instances of PRESERVE8 to .eabi_attribute Tag_ABI_align_preserved, 1.
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