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Download MPLAB® Assembler, Linker and Utilities for PIC32 MCUs User's Guide
Transcript
Assembler Directives 7.13 DIRECTIVES THAT CONTROL CODE GENERATION Directives controlling assembler code-generation behavior are: • • • • • • • • • • .set .set .set .set .set .set .set .set .set .set noat at noautoextend autoextend nomacro macro mips16e nomips16e noreorder reorder .set noat When synthesizing some address formats, the assembler may require a scratch register. By default, the assembler will quietly use the at ($1) register, which is reserved as an assembler temporary by convention. In some cases, the compiler should not use that register. The .set noat directive prevents the assembler from quietly using that register. .set at Allow the assembler to quietly use the at ($1) register. .set noautoextend By default, MIPS16 instructions are automatically extended to 32 bits when necessary. The directive .set noautoextend will turn this off. When .set noautoextend is in effect, any 32-bit instruction must be explicitly extended with the .e modifier (e.g., `li.e $4,1000’). The directive .set autoextend may be used to once again automatically extend instructions when necessary. .set autoextend Enable auto-extension of MIPS16 instructions to 32 bits. .set nomacro The assembler supports synthesized instructions, an instruction mnemonic that synthesizes into multiple machine instructions. For instance, the sleu instruction assembles into an sltu instruction and an xori instruction. The .set nomacro directive causes the assembler to emit a warning message when an instruction expands into more than one machine instruction. .set macro Suppress warnings for synthesized instructions. .set mips16e Assemble with the MIPS16e ISA extension. © 2009 Microchip Technology Inc. DS51833A-page 87
