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fe25521451
To support compressing the debug_line section that contains multiple fragments (due, I believe, to variation in choices of line table encoding depending on the size of instruction ranges in the actual program code) we needed to support compressing multiple MCFragments in a single pass. This patch implements that behavior by mutating the post-relaxed and relocated section to be the compressed form of its former self, including renaming the section. This is a more flexible (and less invasive, to a degree) implementation that will allow for other features such as "use compression only if it's smaller than the uncompressed data". Compressing debug_frame would be a possible further extension to this work, but I've left it for now. The hurdle there is alignment sections - which might require going as far as to refactor MCAssembler.cpp:writeFragment to handle writing to a byte buffer or an MCObjectWriter (there's already a virtual call there, so it shouldn't add substantial compile-time cost) which could in turn involve refactoring MCAsmBackend::writeNopData to use that same abstraction... which involves touching all the backends. This would remove the limited handling of fragment writing seen in ELFObjectWriter.cpp:getUncompressedData which would be nice - but it's more invasive. I did discover that I (perhaps obviously) don't need to handle relocations when I rewrite the fragments - since the relocations have already been applied and computed (and stored into ELFObjectWriter::Relocations) by this stage (necessarily, because we need to have written any immediate values or assembly-time relocations into the data already before we compress it, which we have). The test case doesn't necessarily cover that in detail - I can add more test coverage if that's preferred. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205990 91177308-0d34-0410-b5e6-96231b3b80d8
41 lines
1.2 KiB
ArmAsm
41 lines
1.2 KiB
ArmAsm
// RUN: llvm-mc -filetype=obj -compress-debug-sections -triple x86_64-pc-linux-gnu %s -o %t
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// RUN: llvm-objdump -s %t | FileCheck %s
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// RUN: llvm-dwarfdump -debug-dump=abbrev %t | FileCheck --check-prefix=ABBREV %s
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// REQUIRES: zlib
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// CHECK: Contents of section .zdebug_line:
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// Check for the 'ZLIB' file magic at the start of the section only
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// CHECK-NEXT: ZLIB
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// CHECK-NOT: ZLIB
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// CHECK: Contents of
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// CHECK: Contents of section .zdebug_abbrev:
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// CHECK-NEXT: ZLIB
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// FIXME: Handle compressing alignment fragments to support compressing debug_frame
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// CHECK: Contents of section .debug_frame:
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// CHECK-NOT: ZLIB
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// CHECK: Contents of
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// Decompress one valid dwarf section just to check that this roundtrips
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// ABBREV: Abbrev table for offset: 0x00000000
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// ABBREV: [1] DW_TAG_compile_unit DW_CHILDREN_no
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.section .debug_line,"",@progbits
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.section .debug_abbrev,"",@progbits
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.byte 1 # Abbreviation Code
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.byte 17 # DW_TAG_compile_unit
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.byte 0 # DW_CHILDREN_no
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.byte 0 # EOM(1)
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.byte 0 # EOM(2)
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.text
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foo:
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.cfi_startproc
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.file 1 "Driver.ii"
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.loc 1 2 0
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nop
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.cfi_endproc
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.cfi_sections .debug_frame
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