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[ELF] Change default output section type to SHT_NOBITS

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When an output section has no byte commands and has no input sections then it
would be ideal if the type of the section is SHT_NOBITS so that the file can
take up less space. This change sets the default type of of output sections to
SHT_NOBITS instead of SHT_PROGBITS to allow this. This required some minor test
changes (which double as tests for this new behavior) but extend-pt-load.s had
be changed in a non-trivial way. Since it seems to me that the point of the
test is to point out the consequences of how flags are assigned to output
sections that don't have input sections I changed the test to work and still
show how the memsize of the executable segment was changed.

Differential Revision: https://reviews.llvm.org/D41082

llvm-svn: 320437
This commit is contained in:
Jake Ehrlich
2017-12-11 23:25:27 +00:00
parent 6074e6b094
commit 0ca350a92d
7 changed files with 10 additions and 9 deletions
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2
lld/ELF/LinkerScript.cpp
View File

@@ -87,7 +87,7 @@ OutputSection *LinkerScript::createOutputSection(StringRef Name,
// There was a forward reference.
Sec = SecRef;
} else {
Sec = make<OutputSection>(Name, SHT_PROGBITS, 0);
Sec = make<OutputSection>(Name, SHT_NOBITS, 0);
if (!SecRef)
SecRef = Sec;
}

2
lld/ELF/OutputSections.cpp
View File

@@ -312,6 +312,8 @@ template <class ELFT> void OutputSection::finalize() {
Sections.push_back(IS);
}
}
if (isa<ByteCommand>(Base) && Type == SHT_NOBITS)
Type = SHT_PROGBITS;
}
if (Flags & SHF_LINK_ORDER) {

2
lld/test/ELF/linkerscript/arm-exidx-order.s
View File

@@ -9,7 +9,7 @@
# CHECK: Section {
# CHECK: Index:
# CHECK: Name: .foo
# CHECK-NEXT: Type: SHT_PROGBITS
# CHECK-NEXT: Type: SHT_NOBITS
# CHECK-NEXT: Flags [
# CHECK-NEXT: SHF_ALLOC
# CHECK-NEXT: ]

7
lld/test/ELF/linkerscript/extend-pt-load.s
View File

@@ -33,18 +33,17 @@
# RUN: .hash : { } \
# RUN: .dynstr : { } \
# RUN: .text : { *(.text) } \
# RUN: . = ALIGN(0x1000); \
# RUN: bar : { HIDDEN(bar_sym = .); } \
# RUN: bar : { . = ALIGN(0x1000); } \
# RUN: .data.rel.ro : { *(.data.rel.ro) } \
# RUN: }" > %t.script
# RUN: ld.lld --hash-style=sysv -o %t2 --script %t.script %t.o -shared
# RUN: llvm-readobj --elf-output-style=GNU -l -s %t2 | FileCheck --check-prefix=CHECK2 %s
# CHECK2: .text PROGBITS 00000000000001bc 0001bc 000001 00 AX
# CHECK2-NEXT: bar PROGBITS 0000000000001000 001000 000000 00 AX
# CHECK2-NEXT: bar NOBITS 00000000000001bd 0001bd 000e43 00 AX
# CHECK2-NEXT: .data.rel.ro PROGBITS 0000000000001000 001000 000001 00 WA
# CHECK2: LOAD 0x000000 0x0000000000000000 0x0000000000000000 0x001000 0x001000 R E
# CHECK2: LOAD 0x000000 0x0000000000000000 0x0000000000000000 0x0001bd 0x001000 R E
# CHECK2-NEXT: LOAD 0x001000 0x0000000000001000 0x0000000000001000 0x000068 0x000068 RW
# If the current behavior becomes a problem we should consider just moving the commands out

2
lld/test/ELF/linkerscript/merge-sections.s
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@@ -36,7 +36,7 @@
# RUN: llvm-readobj -s -t %t2 | FileCheck %s --check-prefix=GC
# GC: Name: .foo
# GC-NEXT: Type: SHT_PROGBITS
# GC-NEXT: Type: SHT_NOBITS
# GC-NEXT: Flags [
# GC-NEXT: SHF_ALLOC
# GC-NEXT: ]

2
lld/test/ELF/linkerscript/symbol-only-flags.s
View File

@@ -10,7 +10,7 @@
# CHECK: Section {
# CHECK: Index:
# CHECK: Name: .foo
# CHECK-NEXT: Type: SHT_PROGBITS
# CHECK-NEXT: Type: SHT_NOBITS
# CHECK-NEXT: Flags [
# CHECK-NEXT: SHF_ALLOC
# CHECK-NEXT: SHF_WRITE

2
lld/test/ELF/linkerscript/symbol-only.s
View File

@@ -12,7 +12,7 @@
# CHECK: Sections:
# CHECK-NEXT: Idx Name Size Address
# CHECK-NEXT: 0 00000000 0000000000000000
# CHECK: abc 00000000 [[ADDR:[0-9a-f]*]] DATA
# CHECK: abc 00000000 [[ADDR:[0-9a-f]*]] BSS
# CHECK-NEXT: bar 00000000 0000000000001000 DATA
# CHECK: SYMBOL TABLE: