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[lld/mac] Don't lose "weak ref" bit when doing LTO 

Fixes #52778.

Probably fixes Chromium crashing on startup on macOS 10.15 (and older) systems
when building with LTO, but I haven't verified that yet.

Differential Revision: https://reviews.llvm.org/D115949
This commit is contained in:
Nico Weber 2021-12-17 12:35:52 -05:00
parent 67bc243535
commit c4b45eeb44
2 changed files with 46 additions and 2 deletions
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3
lld/MachO/InputFiles.cpp
View File

@ -1438,9 +1438,8 @@ static macho::Symbol *createBitcodeSymbol(const lto::InputFile::Symbol &objSym,
BitcodeFile &file) {
StringRef name = saver.save(objSym.getName());
// TODO: support weak references
if (objSym.isUndefined())
return symtab->addUndefined(name, &file, /*isWeakRef=*/false);
return symtab->addUndefined(name, &file, /*isWeakRef=*/objSym.isWeak());
// TODO: Write a test demonstrating why computing isPrivateExtern before
// LTO compilation is important.

45
lld/test/MachO/lto-weak-ref.ll Normal file
View File

@ -0,0 +1,45 @@
; REQUIRES: x86
; RUN: rm -rf %t; split-file %s %t
; RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/dylib.s -o %t/dylib.o
; RUN: %lld -dylib -lSystem %t/dylib.o -o %t/dylib.dylib
;; As baseline, compile the .ll file to a real .o file and check behavior.
; RUN: llc -filetype=obj %t/weak-ref.ll -o %t/obj.o
; RUN: %lld -dylib -lSystem %t/obj.o %t/dylib.dylib -o %t/test.obj
; RUN: llvm-objdump --macho --syms %t/test.obj | FileCheck %s --check-prefixes=WEAK-REF
;; Check that we get the same behavior compiling the .ll file to a bitcode .o
;; file and linking that.
; RUN: opt -module-summary %t/weak-ref.ll -o %t/bitcode.o
; RUN: %lld -dylib -lSystem %t/bitcode.o %t/dylib.dylib -o %t/test.lto
; RUN: llvm-objdump --macho --syms %t/test.lto | FileCheck %s --check-prefixes=WEAK-REF
; WEAK-REF: SYMBOL TABLE:
; WEAK-REF: w *UND* _my_weak_extern_function
;--- dylib.s
.globl _my_weak_extern_function
_my_weak_extern_function:
ret
;--- weak-ref.ll
target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.15.0"
declare extern_weak void @my_weak_extern_function()
; Function Attrs: noinline nounwind optnone ssp uwtable
define i32 @bar(i1 zeroext %0) {
entry:
br i1 %0, label %if.then, label %if.end
if.then: ; preds = %entry
call void @my_weak_extern_function()
br label %if.end
if.end: ; preds = %if.then, %entry
ret i32 0
}