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[LTO] Enable module summary emission by default for regular LTO 

Summary:
With D33921, we gained the ability to have module summaries in regular
LTO modules without triggering ThinLTO compilation. Module summaries in
regular LTO allow garbage collection (dead stripping) before LTO
compilation and thus open up additional optimization opportunities.

This patch enables summary emission in regular LTO for all targets
except ld64-based ones (which use the legacy LTO API).

Reviewers: pcc, tejohnson, mehdi_amini

Subscribers: inglorion, eraman, cfe-commits

Differential Revision: https://reviews.llvm.org/D34156

llvm-svn: 335284
This commit is contained in:
Tobias Edler von Koch 2018-06-21 20:20:41 +00:00
parent a76b70069d
commit 9a8be606f3
6 changed files with 49 additions and 18 deletions
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2
clang/include/clang/Frontend/CodeGenOptions.def
View File

@ -110,7 +110,7 @@ CODEGENOPT(LessPreciseFPMAD , 1, 0) ///< Enable less precise MAD instructions t
///< be generated.
CODEGENOPT(PrepareForLTO , 1, 0) ///< Set when -flto is enabled on the
///< compile step.
CODEGENOPT(EmitSummaryIndex, 1, 0) ///< Set when -flto=thin is enabled on the
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).

38
clang/lib/CodeGen/BackendUtil.cpp
View File

@ -524,7 +524,7 @@ void EmitAssemblyHelper::CreatePasses(legacy::PassManager &MPM,
PMBuilder.Inliner = createFunctionInliningPass(
CodeGenOpts.OptimizationLevel, CodeGenOpts.OptimizeSize,
(!CodeGenOpts.SampleProfileFile.empty() &&
CodeGenOpts.EmitSummaryIndex));
CodeGenOpts.PrepareForThinLTO));
}
PMBuilder.OptLevel = CodeGenOpts.OptimizationLevel;
@ -534,7 +534,7 @@ void EmitAssemblyHelper::CreatePasses(legacy::PassManager &MPM,
PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;
PMBuilder.MergeFunctions = CodeGenOpts.MergeFunctions;
PMBuilder.PrepareForThinLTO = CodeGenOpts.EmitSummaryIndex;
PMBuilder.PrepareForThinLTO = CodeGenOpts.PrepareForThinLTO;
PMBuilder.PrepareForLTO = CodeGenOpts.PrepareForLTO;
PMBuilder.RerollLoops = CodeGenOpts.RerollLoops;
@ -776,7 +776,7 @@ void EmitAssemblyHelper::EmitAssembly(BackendAction Action,
break;
case Backend_EmitBC:
if (CodeGenOpts.EmitSummaryIndex) {
if (CodeGenOpts.PrepareForThinLTO) {
if (!CodeGenOpts.ThinLinkBitcodeFile.empty()) {
ThinLinkOS = openOutputFile(CodeGenOpts.ThinLinkBitcodeFile);
if (!ThinLinkOS)
@ -784,10 +784,20 @@ void EmitAssemblyHelper::EmitAssembly(BackendAction Action,
}
PerModulePasses.add(createWriteThinLTOBitcodePass(
*OS, ThinLinkOS ? &ThinLinkOS->os() : nullptr));
}
else
} else {
// Emit a module summary by default for Regular LTO except for ld64
// targets
bool EmitLTOSummary =
(CodeGenOpts.PrepareForLTO &&
llvm::Triple(TheModule->getTargetTriple()).getVendor() !=
llvm::Triple::Apple);
if (EmitLTOSummary && !TheModule->getModuleFlag("ThinLTO"))
TheModule->addModuleFlag(Module::Error, "ThinLTO", uint32_t(0));
PerModulePasses.add(
createBitcodeWriterPass(*OS, CodeGenOpts.EmitLLVMUseLists));
createBitcodeWriterPass(*OS, CodeGenOpts.EmitLLVMUseLists,
EmitLTOSummary));
}
break;
case Backend_EmitLL:
@ -935,7 +945,7 @@ void EmitAssemblyHelper::EmitAssemblyWithNewPassManager(
ModulePassManager MPM(CodeGenOpts.DebugPassManager);
if (!CodeGenOpts.DisableLLVMPasses) {
bool IsThinLTO = CodeGenOpts.EmitSummaryIndex;
bool IsThinLTO = CodeGenOpts.PrepareForThinLTO;
bool IsLTO = CodeGenOpts.PrepareForLTO;
if (CodeGenOpts.OptimizationLevel == 0) {
@ -996,7 +1006,7 @@ void EmitAssemblyHelper::EmitAssemblyWithNewPassManager(
break;
case Backend_EmitBC:
if (CodeGenOpts.EmitSummaryIndex) {
if (CodeGenOpts.PrepareForThinLTO) {
if (!CodeGenOpts.ThinLinkBitcodeFile.empty()) {
ThinLinkOS = openOutputFile(CodeGenOpts.ThinLinkBitcodeFile);
if (!ThinLinkOS)
@ -1005,9 +1015,17 @@ void EmitAssemblyHelper::EmitAssemblyWithNewPassManager(
MPM.addPass(ThinLTOBitcodeWriterPass(*OS, ThinLinkOS ? &ThinLinkOS->os()
: nullptr));
} else {
// Emit a module summary by default for Regular LTO except for ld64
// targets
bool EmitLTOSummary =
(CodeGenOpts.PrepareForLTO &&
llvm::Triple(TheModule->getTargetTriple()).getVendor() !=
llvm::Triple::Apple);
if (EmitLTOSummary && !TheModule->getModuleFlag("ThinLTO"))
TheModule->addModuleFlag(Module::Error, "ThinLTO", uint32_t(0));
MPM.addPass(BitcodeWriterPass(*OS, CodeGenOpts.EmitLLVMUseLists,
CodeGenOpts.EmitSummaryIndex,
CodeGenOpts.EmitSummaryIndex));
EmitLTOSummary));
}
break;

2
clang/lib/CodeGen/CGDebugInfo.cpp
View File

@ -578,7 +578,7 @@ void CGDebugInfo::CreateCompileUnit() {
CSInfo,
getSource(SM, SM.getMainFileID())),
CGOpts.EmitVersionIdentMetadata ? Producer : "",
LO.Optimize || CGOpts.PrepareForLTO || CGOpts.EmitSummaryIndex,
LO.Optimize || CGOpts.PrepareForLTO || CGOpts.PrepareForThinLTO,
CGOpts.DwarfDebugFlags, RuntimeVers,
CGOpts.EnableSplitDwarf ? "" : CGOpts.SplitDwarfFile, EmissionKind,
0 /* DWOid */, CGOpts.SplitDwarfInlining, CGOpts.DebugInfoForProfiling,

4
clang/lib/Frontend/CompilerInvocation.cpp
View File

@ -749,11 +749,11 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
Opts.ProfileSampleAccurate = Args.hasArg(OPT_fprofile_sample_accurate);
Opts.PrepareForLTO = Args.hasArg(OPT_flto, OPT_flto_EQ);
Opts.EmitSummaryIndex = false;
Opts.PrepareForThinLTO = false;
if (Arg *A = Args.getLastArg(OPT_flto_EQ)) {
StringRef S = A->getValue();
if (S == "thin")
Opts.EmitSummaryIndex = true;
Opts.PrepareForThinLTO = true;
else if (S != "full")
Diags.Report(diag::err_drv_invalid_value) << A->getAsString(Args) << S;
}

17
clang/test/CodeGen/emit-summary-index.c Normal file
View File

@ -0,0 +1,17 @@
// ; Check that the -flto=thin option emits a ThinLTO summary
// RUN: %clang_cc1 -flto=thin -emit-llvm-bc < %s | llvm-bcanalyzer -dump | FileCheck %s
// CHECK: <GLOBALVAL_SUMMARY_BLOCK
//
// ; Check that we do not emit a summary for regular LTO on Apple platforms
// RUN: %clang_cc1 -flto -triple x86_64-apple-darwin -emit-llvm-bc < %s | llvm-bcanalyzer -dump | FileCheck --check-prefix=LTO %s
// LTO-NOT: GLOBALVAL_SUMMARY_BLOCK
//
// ; Check that we emit a summary for regular LTO by default elsewhere
// RUN: %clang_cc1 -flto -triple x86_64-pc-linux-gnu -emit-llvm-bc < %s | llvm-bcanalyzer -dump | FileCheck --check-prefix=LTOINDEX %s
// LTOINDEX: <FULL_LTO_GLOBALVAL_SUMMARY_BLOCK
//
// ; Simulate -save-temps and check that it works (!"ThinLTO" module flag not added multiple times)
// RUN: %clang_cc1 -flto -triple x86_64-pc-linux-gnu -emit-llvm-bc -disable-llvm-passes < %s -o %t.bc
// RUN: %clang_cc1 -flto -triple x86_64-pc-linux-gnu -emit-llvm-bc -x ir < %t.bc | llvm-bcanalyzer -dump | FileCheck --check-prefix=LTOINDEX %s
int main() {}

4
clang/test/Misc/thinlto.c
View File

@ -1,4 +0,0 @@
// RUN: %clang_cc1 -flto=thin -emit-llvm-bc < %s | llvm-bcanalyzer -dump | FileCheck %s
// ; Check that the -flto=thin option emits a summary
// CHECK: <GLOBALVAL_SUMMARY_BLOCK
int main() {}