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[LTO] Handle __imp_ (dllimport) symbols consistently with lld

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Summary:
Similar to what lld already does for dllimport symbols which are
prefaced with __imp_ (see lld patch r240620), strip off the __imp_
prefix in LTO. Otherwise we can get 2 separate GlobalResolution for
a single symbol, the dllimport declaration, and the definition, which
leads to incorrect LTO handling.

Fixes PR38105.

Reviewers: pcc

Subscribers: mehdi_amini, inglorion, steven_wu, dexonsmith, llvm-commits

Differential Revision: https://reviews.llvm.org/D49138

llvm-svn: 337762
This commit is contained in:
Teresa Johnson 2018-07-23 22:33:57 +00:00
parent 5a7306f043
commit 30f6ebce41
3 changed files with 55 additions and 1 deletions
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9
lib/LTO/LTO.cpp
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@ -428,7 +428,14 @@ void LTO::addModuleToGlobalRes(ArrayRef<InputFile::Symbol> Syms,
assert(ResI != ResE);
SymbolResolution Res = *ResI++;
auto &GlobalRes = GlobalResolutions[Sym.getName()];
StringRef Name = Sym.getName();
Triple TT(RegularLTO.CombinedModule->getTargetTriple());
// Strip the __imp_ prefix from COFF dllimport symbols (similar to the
// way they are handled by lld), otherwise we can end up with two
// global resolutions (one with and one for a copy of the symbol without).
if (TT.isOSBinFormatCOFF() && Name.startswith("__imp_"))
Name = Name.substr(strlen("__imp_"));
auto &GlobalRes = GlobalResolutions[Name];
GlobalRes.UnnamedAddr &= Sym.isUnnamedAddr();
if (Res.Prevailing) {
assert(!GlobalRes.Prevailing &&

17
test/LTO/X86/Inputs/dllimport.ll Normal file
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@ -0,0 +1,17 @@
; ModuleID = 'b.obj'
source_filename = "b.cpp"
target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-windows-msvc19.11.0"
; Function Attrs: norecurse nounwind readnone sspstrong uwtable
define dso_local i32 @"?foo@@YAHXZ"() local_unnamed_addr {
entry:
ret i32 42
}
!llvm.module.flags = !{!1}
!1 = !{i32 1, !"ThinLTO", i32 0}
^0 = module: (path: "b.obj", hash: (0, 0, 0, 0, 0))
^1 = gv: (name: "?foo@@YAHXZ", summaries: (function: (module: ^0, flags: (linkage: external, notEligibleToImport: 1, live: 0, dsoLocal: 1), insts: 1, funcFlags: (readNone: 1, readOnly: 0, noRecurse: 1, returnDoesNotAlias: 0)))) ; guid = 2709792123250749187

30
test/LTO/X86/dllimport.ll Normal file
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@ -0,0 +1,30 @@
; Test requiring LTO to remove the __imp_ prefix for locally imported COFF
; symbols (mirroring how lld handles these symbols).
; RUN: llvm-as %s -o %t.obj
; RUN: llvm-as %S/Inputs/dllimport.ll -o %t2.obj
; RUN: llvm-lto2 run -r=%t.obj,main,px -r %t.obj,__imp_?foo@@YAHXZ -r %t2.obj,?foo@@YAHXZ,p -o %t3 %t.obj %t2.obj -save-temps
; RUN: llvm-dis %t3.0.0.preopt.bc -o - | FileCheck %s
; CHECK: define dso_local i32 @"?foo@@YAHXZ"()
; ModuleID = 'a.obj'
source_filename = "a.cpp"
target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-windows-msvc19.11.0"
; Function Attrs: norecurse nounwind sspstrong uwtable
define dso_local i32 @main() local_unnamed_addr {
entry:
%call = tail call i32 @"?foo@@YAHXZ"()
ret i32 %call
}
declare dllimport i32 @"?foo@@YAHXZ"() local_unnamed_addr
!llvm.module.flags = !{!1}
!1 = !{i32 1, !"ThinLTO", i32 0}
^0 = module: (path: "a.obj", hash: (0, 0, 0, 0, 0))
^1 = gv: (name: "?foo@@YAHXZ") ; guid = 2709792123250749187
^2 = gv: (name: "main", summaries: (function: (module: ^0, flags: (linkage: external, notEligibleToImport: 1, live: 0, dsoLocal: 1), insts: 2, funcFlags: (readNone: 0, readOnly: 0, noRecurse: 1, returnDoesNotAlias: 0), calls: ((callee: ^1))))) ; guid = 15822663052811949562