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[LTO] Add option to enable LTOUnit splitting, and disable unless needed 

Summary:
Adds a new -f[no]split-lto-unit flag that is disabled by default to
control module splitting during ThinLTO. It is automatically enabled
for -fsanitize=cfi and -fwhole-program-vtables.

The new EnableSplitLTOUnit codegen flag is passed down to llvm
via a new module flag of the same name.

Depends on D53890.

Reviewers: pcc

Subscribers: ormris, mehdi_amini, inglorion, eraman, steven_wu, dexonsmith, cfe-commits, llvm-commits

Differential Revision: https://reviews.llvm.org/D53891

llvm-svn: 350949
This commit is contained in:
Teresa Johnson 2019-01-11 18:32:07 +00:00
parent 290a839891
commit 84cecfcb3d
12 changed files with 61 additions and 13 deletions
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4
clang/include/clang/Basic/CodeGenOptions.def
View File

@ -116,6 +116,10 @@ CODEGENOPT(PrepareForThinLTO , 1, 0) ///< Set when -flto=thin is enabled on the
///< compile step.
CODEGENOPT(LTOUnit, 1, 0) ///< Emit IR to support LTO unit features (CFI, whole
///< program vtable opt).
CODEGENOPT(EnableSplitLTOUnit, 1, 0) ///< Enable LTO unit splitting to support
/// CFI and traditional whole program
/// devirtualization that require whole
/// program IR support.
CODEGENOPT(IncrementalLinkerCompatible, 1, 0) ///< Emit an object file which can
///< be used with an incremental
///< linker.

5
clang/include/clang/Driver/Options.td
View File

@ -1776,6 +1776,11 @@ def fwhole_program_vtables : Flag<["-"], "fwhole-program-vtables">, Group<f_Grou
HelpText<"Enables whole-program vtable optimization. Requires -flto">;
def fno_whole_program_vtables : Flag<["-"], "fno-whole-program-vtables">, Group<f_Group>,
Flags<[CoreOption]>;
def fsplit_lto_unit : Flag<["-"], "fsplit-lto-unit">, Group<f_Group>,
Flags<[CoreOption, CC1Option]>,
HelpText<"Enables splitting of the LTO unit.">;
def fno_split_lto_unit : Flag<["-"], "fno-split-lto-unit">, Group<f_Group>,
Flags<[CoreOption]>;
def fforce_emit_vtables : Flag<["-"], "fforce-emit-vtables">, Group<f_Group>,
Flags<[CC1Option]>,
HelpText<"Emits more virtual tables to improve devirtualization">;

1
clang/include/clang/Driver/SanitizerArgs.h
View File

@ -81,6 +81,7 @@ class SanitizerArgs {
bool requiresPIE() const;
bool needsUnwindTables() const;
bool needsLTO() const;
bool linkCXXRuntimes() const { return LinkCXXRuntimes; }
bool hasCrossDsoCfi() const { return CfiCrossDso; }
bool hasAnySanitizer() const { return !Sanitizers.empty(); }

26
clang/lib/CodeGen/BackendUtil.cpp
View File

@ -814,6 +814,8 @@ void EmitAssemblyHelper::EmitAssembly(BackendAction Action,
if (!ThinLinkOS)
return;
}
TheModule->addModuleFlag(Module::Error, "EnableSplitLTOUnit",
CodeGenOpts.EnableSplitLTOUnit);
PerModulePasses.add(createWriteThinLTOBitcodePass(
*OS, ThinLinkOS ? &ThinLinkOS->os() : nullptr));
} else {
@ -824,12 +826,15 @@ void EmitAssemblyHelper::EmitAssembly(BackendAction Action,
!CodeGenOpts.DisableLLVMPasses &&
llvm::Triple(TheModule->getTargetTriple()).getVendor() !=
llvm::Triple::Apple);
if (EmitLTOSummary && !TheModule->getModuleFlag("ThinLTO"))
if (EmitLTOSummary) {
if (!TheModule->getModuleFlag("ThinLTO"))
TheModule->addModuleFlag(Module::Error, "ThinLTO", uint32_t(0));
TheModule->addModuleFlag(Module::Error, "EnableSplitLTOUnit",
CodeGenOpts.EnableSplitLTOUnit);
}
PerModulePasses.add(
createBitcodeWriterPass(*OS, CodeGenOpts.EmitLLVMUseLists,
EmitLTOSummary));
PerModulePasses.add(createBitcodeWriterPass(
*OS, CodeGenOpts.EmitLLVMUseLists, EmitLTOSummary));
}
break;
@ -1054,6 +1059,8 @@ void EmitAssemblyHelper::EmitAssemblyWithNewPassManager(
if (!ThinLinkOS)
return;
}
TheModule->addModuleFlag(Module::Error, "EnableSplitLTOUnit",
CodeGenOpts.EnableSplitLTOUnit);
MPM.addPass(ThinLTOBitcodeWriterPass(*OS, ThinLinkOS ? &ThinLinkOS->os()
: nullptr));
} else {
@ -1064,11 +1071,14 @@ void EmitAssemblyHelper::EmitAssemblyWithNewPassManager(
!CodeGenOpts.DisableLLVMPasses &&
llvm::Triple(TheModule->getTargetTriple()).getVendor() !=
llvm::Triple::Apple);
if (EmitLTOSummary && !TheModule->getModuleFlag("ThinLTO"))
if (EmitLTOSummary) {
if (!TheModule->getModuleFlag("ThinLTO"))
TheModule->addModuleFlag(Module::Error, "ThinLTO", uint32_t(0));
MPM.addPass(BitcodeWriterPass(*OS, CodeGenOpts.EmitLLVMUseLists,
EmitLTOSummary));
TheModule->addModuleFlag(Module::Error, "EnableSplitLTOUnit",
CodeGenOpts.EnableSplitLTOUnit);
}
MPM.addPass(
BitcodeWriterPass(*OS, CodeGenOpts.EmitLLVMUseLists, EmitLTOSummary));
}
break;

2
clang/lib/Driver/SanitizerArgs.cpp
View File

@ -207,6 +207,8 @@ bool SanitizerArgs::needsUnwindTables() const {
return Sanitizers.Mask & NeedsUnwindTables;
}
bool SanitizerArgs::needsLTO() const { return Sanitizers.Mask & NeedsLTO; }
SanitizerArgs::SanitizerArgs(const ToolChain &TC,
const llvm::opt::ArgList &Args) {
SanitizerMask AllRemove = 0; // During the loop below, the accumulated set of

11
clang/lib/Driver/ToolChains/Clang.cpp
View File

@ -5226,6 +5226,17 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
CmdArgs.push_back("-fwhole-program-vtables");
}
bool RequiresSplitLTOUnit = WholeProgramVTables || Sanitize.needsLTO();
bool SplitLTOUnit =
Args.hasFlag(options::OPT_fsplit_lto_unit,
options::OPT_fno_split_lto_unit, RequiresSplitLTOUnit);
if (RequiresSplitLTOUnit && !SplitLTOUnit)
D.Diag(diag::err_drv_argument_not_allowed_with)
<< "-fno-split-lto-unit"
<< (WholeProgramVTables ? "-fwhole-program-vtables" : "-fsanitize=cfi");
if (SplitLTOUnit)
CmdArgs.push_back("-fsplit-lto-unit");
if (Arg *A = Args.getLastArg(options::OPT_fexperimental_isel,
options::OPT_fno_experimental_isel)) {
CmdArgs.push_back("-mllvm");

1
clang/lib/Frontend/CompilerInvocation.cpp
View File

@ -907,6 +907,7 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
Diags.Report(diag::err_drv_invalid_value) << A->getAsString(Args) << S;
}
Opts.LTOUnit = Args.hasFlag(OPT_flto_unit, OPT_fno_lto_unit, false);
Opts.EnableSplitLTOUnit = Args.hasArg(OPT_fsplit_lto_unit);
if (Arg *A = Args.getLastArg(OPT_fthinlto_index_EQ)) {
if (IK.getLanguage() != InputKind::LLVM_IR)
Diags.Report(diag::err_drv_argument_only_allowed_with)

2
clang/test/CodeGen/thinlto-distributed-cfi-devirt.ll
View File

@ -4,7 +4,7 @@
; It additionally enables -fwhole-program-vtables to get more information in
; TYPE_IDs of GLOBALVAL_SUMMARY_BLOCK.
; RUN: opt -thinlto-bc -o %t.o %s
; RUN: opt -thinlto-bc -thinlto-split-lto-unit -o %t.o %s
; FIXME: Fix machine verifier issues and remove -verify-machineinstrs=0. PR39436.
; RUN: llvm-lto2 run -thinlto-distributed-indexes %t.o \

2
clang/test/CodeGen/thinlto-distributed-cfi.ll
View File

@ -2,7 +2,7 @@
; Backend test for distribute ThinLTO with CFI.
; RUN: opt -thinlto-bc -o %t.o %s
; RUN: opt -thinlto-bc -thinlto-split-lto-unit -o %t.o %s
; RUN: llvm-lto2 run -thinlto-distributed-indexes %t.o \
; RUN: -o %t2.index \

2
clang/test/CodeGenCXX/no-lto-unit.cpp
View File

@ -2,6 +2,8 @@
// RUN: llvm-dis -o - %t | FileCheck %s
// RUN: %clang_cc1 -flto=thin -flto-unit -fno-lto-unit -triple x86_64-unknown-linux -fvisibility hidden -emit-llvm-bc -o %t %s
// RUN: llvm-dis -o - %t | FileCheck %s
// RUN: llvm-bcanalyzer -dump %t | FileCheck %s --check-prefix=NOLTOUNIT
// NOLTOUNIT: <FLAGS op0=0/>
// CHECK-NOT: !type
class A {

4
clang/test/CodeGenCXX/type-metadata-thinlto.cpp
View File

@ -1,5 +1,7 @@
// RUN: %clang_cc1 -flto=thin -flto-unit -triple x86_64-unknown-linux -fvisibility hidden -emit-llvm-bc -o %t %s
// RUN: %clang_cc1 -flto=thin -flto-unit -fsplit-lto-unit -triple x86_64-unknown-linux -fvisibility hidden -emit-llvm-bc -o %t %s
// RUN: llvm-modextract -o - -n 1 %t | llvm-dis | FileCheck %s
// RUN: llvm-modextract -b -o - -n 1 %t | llvm-bcanalyzer -dump | FileCheck %s --check-prefix=LTOUNIT
// LTOUNIT: <FLAGS op0=8/>
// CHECK: @_ZTV1A = linkonce_odr
class A {

10
clang/test/Driver/split-lto-unit.c Normal file
View File

@ -0,0 +1,10 @@
// RUN: %clang -target x86_64-unknown-linux -### %s -flto=thin 2>&1 | FileCheck --check-prefix=NOUNIT %s
// RUN: %clang -target x86_64-unknown-linux -### %s -flto=thin -fsplit-lto-unit 2>&1 | FileCheck --check-prefix=UNIT %s
// RUN: %clang -target x86_64-unknown-linux -### %s -flto=thin -fno-split-lto-unit 2>&1 | FileCheck --check-prefix=NOUNIT %s
// RUN: %clang -target x86_64-unknown-linux -### %s -flto=thin -fno-split-lto-unit -fwhole-program-vtables 2>&1 | FileCheck --check-prefix=ERROR1 %s
// RUN: %clang -target x86_64-unknown-linux -### %s -flto=thin -fno-split-lto-unit -fsanitize=cfi 2>&1 | FileCheck --check-prefix=ERROR2 %s
// UNIT: "-fsplit-lto-unit"
// NOUNIT-NOT: "-fsplit-lto-unit"
// ERROR1: error: invalid argument '-fno-split-lto-unit' not allowed with '-fwhole-program-vtables'
// ERROR2: error: invalid argument '-fno-split-lto-unit' not allowed with '-fsanitize=cfi'