comp3221microprocessorsandembeddedsystems-資料下載頁
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【正文】 .global main main: : ldr r2, [pc, offset] : end: .word 4118633130 Offset = end (pc + 8) COMP3221 Saeid Nooshabadi Pseudoinstruction Replacement (6/6) ? Recall: ldr/str rdest, label = load/stores a value at label (address) in the same segment. Converts to ldr rdest, [pc, offset] instruction, where offset is puted by (address@label [pc + 8]). offset range ? 212 (?4 Kbytes) ?ldr rdest, =label = load address of ANY label ?PC relative LDR instruction will be generated to load the address of the label from literal pool inserted at the end of the text segment. COMP3221 Saeid Nooshabadi Handling Addresses by Assembler (1/2) 176。Branches: b, amp。 bl (branch and link) b/bl label 176。Such branches are normally taken to a label (address) labels at fixed locations, in the same module (file) or other modules (eg. Call to functions in other modules) 176。The address of the label is absolute COMP3221 Saeid Nooshabadi Handling Addresses by Assembler (2/2) 176。Loads and stores to variables in static area ldr/str Rdest, [pc, offset] ? Such addresses are stored in the literal pool by the piler/Assembler ? The reference to to the literal pool is via PC relative addressing ? Sometimes they are referenced via Static Base Pointer (SB) ldr/str Rdest, [sb, offset] 176。Loads and stores to local variables ? Such variables are put direct on registers or on stack and are referenced via sp or fp. COMP3221 Saeid Nooshabadi Reading Material 176。Reading assignment: ? David Patterson and John Hennessy: Computer Organisation amp。 Design: The HW/SW Interface, 2nd Ed Man Kaufmann, 1998, ISBN: 1 55860 491 X. (, ) 176。Steve Furber: ARM System OnChip。 2nd Ed, AddisonWesley, 2022, ISBN: 0201675196. chapter 2, section COMP3221 Saeid Nooshabadi Things to Remember 176。Compiler converts a single HLL file into a single assembly language file. 176。Assembler removes pseudos, converts it can to machine language. This changes each .s file into a .o file. 176。Linker bines several .o files and resolves absolute addresses. 176。Loader loads executable into memory and begins execution.
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