a0d8a53c7d
Mapping symbols [1] are special ELF symbols that can be inserted to indicate regions of code or data. A sequence of data bytes is indicated by a `$d` (or `$d.<any>`) symbol pointing to its start while a sequence of instructions uses a `$x` (or `$x.<any>`) symbol. This can be used, for example, to assist disassembling a memory region containing both data and code. This patch implements mapping symbols for RISC-V, copying the implementation mostly from the AArch64 target. Note that the `$x<ISA>` mapping symbol, indicating an instruction sequence with a specific ISA extension, is not implemented by this patch. As far as I can tell, binutils doesn't implement this yet either. Note that this patch uses the same symbol naming convention as the AArch64 target: always use `$x.i` and `$d.i` (where `i` is a monotonically increasing counter). This differs from binutils where all symbols are named `$x` or `$d` (causing multiple symbol having the same name). I'm not not sure whether it makes more sense to avoid duplicate symbol names or be consistent with binutils. Note that the handling of nop-slides inserted for alignment differs from binutils: binutils always marks the nops as instructions (`$x`) while this patch doesn't insert a symbol for the nops (so the last inserted symbol is used). I believe binutil's behavior makes most sense but this seems difficult to implement in LLVM as the insertion of nops is handled by `RISCVAsmBackend`. At this point, inserting ELF symbols seems impossible. Any ideas for how to handle this would be appreciated. [1]: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-elf.adoc#mapping-symbol Depends on D156190 and D156236 Differential Revision: https://reviews.llvm.org/D153260
28 lines
738 B
ArmAsm
28 lines
738 B
ArmAsm
# RUN: llvm-mc -triple=riscv32 -filetype=obj %s | llvm-readelf -Ss - | FileCheck %s
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# RUN: llvm-mc -triple=riscv64 -filetype=obj %s | llvm-readelf -Ss - | FileCheck %s
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.text
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# $x at 0x0000
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nop
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# $d at 0x0004
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.ascii "012"
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.byte 1
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.hword 2
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.word 4
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.single 4.0
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.double 8.0
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.space 10
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.zero 3
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.fill 10, 2, 42
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.org 100, 12
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# $x at 0x0064
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nop
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## Capture section index.
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# CHECK: [[#TEXT:]]] .text
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# CHECK: Value Size Type Bind Vis Ndx Name
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# CHECK: 00000000 0 NOTYPE LOCAL DEFAULT [[#TEXT]] $x
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# CHECK: 00000004 0 NOTYPE LOCAL DEFAULT [[#TEXT]] $d
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# CHECK: 00000064 0 NOTYPE LOCAL DEFAULT [[#TEXT]] $x
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