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[lld] Discard SHT_LLVM_LTO sections in relocatable links #92825

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Merged
merged 6 commits into from
Jun 8, 2024
Merged

[lld] Discard SHT_LLVM_LTO sections in relocatable links #92825

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fcca6f4
[𝘀𝗽𝗿] initial version
ilovepi May 20, 2024
d4228eb
[𝘀𝗽𝗿] changes to main this commit is based on
ilovepi May 20, 2024
0b9155f
Fix fallthrough and update comment
ilovepi May 21, 2024
35afa32
[𝘀𝗽𝗿] changes introduced through rebase
ilovepi May 21, 2024
9743e09
Rebase and update tests
ilovepi May 21, 2024
9389967
Rebase on main and fix typos in test
ilovepi Jun 5, 2024
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10 changes: 10 additions & 0 deletions lld/ELF/InputFiles.cpp
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Expand Up @@ -832,6 +832,16 @@ void ObjFile<ELFT>::initializeSections(bool ignoreComdats,
this->sections[i] =
createInputSection(i, sec, check(obj.getSectionName(sec, shstrtab)));
break;
case SHT_LLVM_LTO:
// Discard .llvm.lto in a relocatable link that does not use the bitcode.
// The concatenated output does not properly reflect the linking
// semantics. In addition, since we do not use the bitcode wrapper format,
// the concatenated raw bitcode would be invalid.
if (config->relocatable && !config->fatLTOObjects) {
sections[i] = &InputSection::discarded;
break;
}
[[fallthrough]];
default:
this->sections[i] =
createInputSection(i, sec, check(obj.getSectionName(sec, shstrtab)));
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38 changes: 38 additions & 0 deletions lld/test/ELF/fatlto/fatlto.test
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Expand Up @@ -49,6 +49,22 @@
; RUN: ld.lld -o %t/foo-fatLTO.archive %t/a.a %t/main-LTO.bc --fat-lto-objects
; RUN: cmp %t/foo-fatLTO.archive %t/foo-LTO

;; Test FatLTO works with relocatable links using PIC objects
; RUN: opt < %t/a-LTO.ll -passes="embed-bitcode<thinlto;emit-summary>" | llc --relocation-model=pic --filetype=obj -o %t/a-fat-pic.o
; RUN: llvm-readobj -S %t/a-fat-pic.o | FileCheck --check-prefix=HAS_LLVM_LTO %s

; RUN: opt < %t/b-LTO.ll -passes="embed-bitcode<thinlto;emit-summary>" | llc --relocation-model=pic --filetype=obj -o %t/b-fat-pic.o
; RUN: llvm-readobj -S %t/b-fat-pic.o | FileCheck --check-prefix=HAS_LLVM_LTO %s

; RUN: llvm-ar rcs %t/fat.pic.archive %t/a-fat-pic.o %t/b-fat-pic.o
; RUN: llvm-readobj -S %t/fat.pic.archive | FileCheck --check-prefix=HAS_LLVM_LTO %s

; RUN: ld.lld --whole-archive %t/fat.pic.archive -r -o %t/fat-pic-relocatable.o
; RUN: llvm-readobj -S %t/fat-pic-relocatable.o | FileCheck --check-prefix=CHECK-NON-LTO-TARGET %s

; HAS_LLVM_LTO: Name: .llvm.lto
; HAS_LLVM_LTO: Type: SHT_LLVM_LTO

;--- a-LTO.ll
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
Expand All @@ -71,6 +87,28 @@ attributes #0 = { noinline nounwind uwtable }
!5 = !{i32 1, !"ThinLTO", i32 0}
!6 = !{i32 1, !"EnableSplitLTOUnit", i32 1}

;--- b-LTO.ll
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

; Function Attrs: noinline nounwind uwtable
define dso_local i32 @foo() #0 {
entry:
ret i32 0
}

attributes #0 = { noinline nounwind uwtable }

!llvm.module.flags = !{!0, !1, !2, !3, !4, !5, !6}

!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{i32 7, !"PIC Level", i32 2}
!2 = !{i32 7, !"PIE Level", i32 2}
!3 = !{i32 7, !"uwtable", i32 2}
!4 = !{i32 7, !"frame-pointer", i32 2}
!5 = !{i32 1, !"ThinLTO", i32 0}
!6 = !{i32 1, !"EnableSplitLTOUnit", i32 1}

;--- main-LTO.ll
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
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3 changes: 3 additions & 0 deletions llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
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Expand Up @@ -527,6 +527,9 @@ static unsigned getELFSectionType(StringRef Name, SectionKind K) {
if (K.isBSS() || K.isThreadBSS())
return ELF::SHT_NOBITS;

if(hasPrefix(Name, ".llvm.lto"))
return ELF::SHT_LLVM_LTO;

return ELF::SHT_PROGBITS;
}

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2 changes: 1 addition & 1 deletion llvm/test/CodeGen/X86/fat-lto-section.ll
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Expand Up @@ -5,6 +5,6 @@
; RUN: | FileCheck %s --check-prefix=EXCLUDE

; EXCLUDE: Name Type {{.*}} ES Flg Lk Inf Al
; EXCLUDE: .llvm.lto PROGBITS {{.*}} 00 E 0 0 1
; EXCLUDE: .llvm.lto LLVM_LTO {{.*}} 00 E 0 0 1

@a = global i32 1
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