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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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Original file line number Diff line number Diff line change
Expand Up @@ -844,6 +844,16 @@ 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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17 changes: 4 additions & 13 deletions lld/test/ELF/fatlto/fatlto.test
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,6 @@
; RUN: opt < a-LTO.ll --module-summary -o a-fatLTO.bc
; RUN: llvm-objcopy --add-section=.llvm.lto=a-fatLTO.bc --set-section-flags=.llvm.lto=exclude --set-section-type=.llvm.lto=0x6fff4c0c a-fatLTO.o


; RUN: llc main-LTO.ll --filetype=obj -o main-fatLTO.o --relocation-model=pic
; RUN: opt < main-LTO.ll --module-summary -o main-fatLTO.bc
; RUN: llvm-objcopy --add-section=.llvm.lto=main-fatLTO.bc --set-section-flags=.llvm.lto=exclude --set-section-type=.llvm.lto=0x6fff4c0c main-fatLTO.o
Expand All @@ -17,11 +16,6 @@
; RUN: llvm-readelf -S main-fatLTO.o | FileCheck --check-prefix=HAS_LLVM_LTO %s

;; Make sure that the section flags are set correctly
; HA_LLVM_LTO: Name: .llvm.lto
; HA_LLVM_LTO-NEXT: Type: SHT_LLVM_LTO
; HA_LLVM_LTO-NEXT: Flags
; HA_LLVM_LTO-NEXT: SHF_EXCLUDE

; HAS_LLVM_LTO: Name Type Address Off Size ES Flg Lk Inf Al
; HAS_LLVM_LTO: .llvm.lto LLVM_LTO {{.*}} 00 WE 0 0 1

Expand Down Expand Up @@ -64,16 +58,13 @@
; RUN: ld.lld -o foo-fatLTO.archive a.a main-LTO.bc --fat-lto-objects
; RUN: cmp foo-fatLTO.archive foo-LTO

;; Test FatLTO works with relocatable links using PIC objects
;; Currently, with PIC relocatable links, FatLTO sections are treated as
;; orphan sections and incorrectly concatenated together. This test verifies
;; the current behavior, but should be fixed to either merge those sections
;; correctly, or to drop them altogether.
;; Test FatLTO works with relocatable links using PIC objects, and that
;; SHT_LLVM_LTO sections are discarded.
; RUN: llvm-ar rcs fatLTO-pic.a a-fatLTO.o main-fatLTO.o
; RUN: llvm-readelf -S fatLTO-pic.a | FileCheck --check-prefix=HAS_LLVM_LTO %s

; RUN: ld.lld --whole-archive fatLTO-pic.a -r -o fatLTO-pic-reolcatable.o
; RUN: llvm-readelf -S fatLTO-pic-reolcatable.o | FileCheck --check-prefix=HAS_LLVM_LTO %s
; RUN: ld.lld --whole-archive fatLTO-pic.a -r -o fatLTO-pic-relocatable.o
; RUN: llvm-readelf -S fatLTO-pic-relocatable.o | FileCheck --check-prefix=CHECK-NON-LTO-TARGET %s

;--- 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"
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