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[ThinLTO] add post-thinlto-merge option to -lto-embed-bitcode 

This will embed bitcode after (Thin)LTO merge, but before optimizations.
In the case the thinlto backend is called from clang, the .llvmcmd
section is also produced. Doing so in the case where the caller is the
linker doesn't yet have a motivation, and would require plumbing through
command line args.

Differential Revision: https://reviews.llvm.org/D87636
This commit is contained in:
Mircea Trofin 2020-09-14 10:45:00 -07:00
parent ae726fecae
commit 61fc10d6a5
8 changed files with 90 additions and 9 deletions
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7
clang/lib/CodeGen/BackendUtil.cpp
View File

@ -1647,9 +1647,10 @@ static void runThinLTOBackend(
Conf.CGFileType = getCodeGenFileType(Action);
break;
}
if (Error E = thinBackend(
Conf, -1, AddStream, *M, *CombinedIndex, ImportList,
ModuleToDefinedGVSummaries[M->getModuleIdentifier()], ModuleMap)) {
if (Error E =
thinBackend(Conf, -1, AddStream, *M, *CombinedIndex, ImportList,
ModuleToDefinedGVSummaries[M->getModuleIdentifier()],
ModuleMap, &CGOpts.CmdArgs)) {
handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) {
errs() << "Error running ThinLTO backend: " << EIB.message() << '\n';
});

9
clang/test/CodeGen/Inputs/start-lib1.ll Normal file
View File

@ -0,0 +1,9 @@
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
declare void @bar()
define void @foo() {
call void @bar()
ret void
}

6
clang/test/CodeGen/Inputs/start-lib2.ll Normal file
View File

@ -0,0 +1,6 @@
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define void @bar() {
ret void
}

30
clang/test/CodeGen/thinlto_embed_bitcode.ll Normal file
View File

@ -0,0 +1,30 @@
; REQUIRES: x86-registered-target
; check the -lto-embed-bitcode=post-thinlto-merge does not perform optimizations
; we expect 't1' - i.e start-lib1.ll's products - have both foo and bar defined,
; but the bar call is still made from foo.
; RUN: opt -module-summary %p/Inputs/start-lib1.ll -o %t1.bc
; RUN: opt -module-summary %p/Inputs/start-lib2.ll -o %t2.bc
; RUN: llvm-lto -thinlto -o %t.o %t1.bc %t2.bc
; RUN: %clang -target x86_64-unknown-linux-gnu -O2 -o %t.o -x ir %t1.bc -c -fthinlto-index=%t.o.thinlto.bc -mllvm -lto-embed-bitcode=post-merge-pre-opt
; RUN: llvm-readelf -S %t.o | FileCheck %s --check-prefixes=CHECK-ELF,CHECK-CMD
; RUN: llvm-objcopy --dump-section=.llvmbc=%t-embedded.bc %t.o /dev/null
; RUN: llvm-dis %t-embedded.bc -o - | FileCheck %s --check-prefixes=CHECK,CHECK-NOOPT
; For the optimized case, we expect the inlining of foo into bar to happen.
; RUN: %clang -target x86_64-unknown-linux-gnu -O2 -o %t.o -x ir %t1.bc -c -fthinlto-index=%t.o.thinlto.bc -mllvm -lto-embed-bitcode=optimized
; RUN: llvm-readelf -S %t.o | FileCheck %s --check-prefixes=CHECK-ELF,CHECK-NO-CMD
; RUN: llvm-objcopy --dump-section=.llvmbc=%t-embedded.bc %t.o /dev/null
; RUN: llvm-dis %t-embedded.bc -o - | FileCheck %s --check-prefixes=CHECK,CHECK-OPT
; CHECK-ELF: .text PROGBITS 0000000000000000 [[#%x,OFF:]] [[#%x,SIZE:]] 00 AX 0
; CHECK-ELF-NEXT: .llvmbc PROGBITS 0000000000000000 [[#%x,OFF:]] [[#%x,SIZE:]] 00 0
; CHECK-ELF-CMD: .llvmcmd
; CHECK-ELF-NO-CMD-NOT: .llvmcmd
; CHECK: define void @foo()
; CHECK-OPT-NEXT: ret void
; CHECK-NOOPT-NEXT: call void @bar()
; CHECK-NOOPT: define available_externally void @bar() !thinlto_src_module !0 {
; CHECK-NOOPT-NEXT: ret void

3
llvm/include/llvm/LTO/LTOBackend.h
View File

@ -44,7 +44,8 @@ Error thinBackend(const Config &C, unsigned Task, AddStreamFn AddStream,
Module &M, const ModuleSummaryIndex &CombinedIndex,
const FunctionImporter::ImportMapTy &ImportList,
const GVSummaryMapTy &DefinedGlobals,
MapVector<StringRef, BitcodeModule> &ModuleMap);
MapVector<StringRef, BitcodeModule> &ModuleMap,
const std::vector<uint8_t> *CmdArgs = nullptr);
Error finalizeOptimizationRemarks(
std::unique_ptr<ToolOutputFile> DiagOutputFile);

34
llvm/lib/LTO/LTOBackend.cpp
View File

@ -50,9 +50,12 @@
using namespace llvm;
using namespace lto;
#define DEBUG_TYPE "lto-backend"
enum class LTOBitcodeEmbedding {
DoNotEmbed = 0,
EmbedOptimized = 1,
EmbedPostMergePreOptimized = 2
};
static cl::opt<LTOBitcodeEmbedding> EmbedBitcode(
@ -60,7 +63,10 @@ static cl::opt<LTOBitcodeEmbedding> EmbedBitcode(
cl::values(clEnumValN(LTOBitcodeEmbedding::DoNotEmbed, "none",
"Do not embed"),
clEnumValN(LTOBitcodeEmbedding::EmbedOptimized, "optimized",
"Embed after all optimization passes")),
"Embed after all optimization passes"),
clEnumValN(LTOBitcodeEmbedding::EmbedPostMergePreOptimized,
"post-merge-pre-opt",
"Embed post merge, but before optimizations")),
cl::desc("Embed LLVM bitcode in object files produced by LTO"));
LLVM_ATTRIBUTE_NORETURN static void reportOpenError(StringRef Path, Twine Msg) {
@ -346,7 +352,25 @@ static void runOldPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
bool opt(const Config &Conf, TargetMachine *TM, unsigned Task, Module &Mod,
bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
const ModuleSummaryIndex *ImportSummary) {
const ModuleSummaryIndex *ImportSummary,
const std::vector<uint8_t> *CmdArgs = nullptr) {
if (EmbedBitcode == LTOBitcodeEmbedding::EmbedPostMergePreOptimized) {
// FIXME: the motivation for capturing post-merge bitcode and command line
// is replicating the compilation environment from bitcode, without needing
// to understand the dependencies (the functions to be imported). This
// assumes a clang - based invocation, case in which we have the command
// line.
// It's not very clear how the above motivation would map in the
// linker-based case, so we currently don't plumb the command line args in
// that case.
if (CmdArgs == nullptr)
LLVM_DEBUG(
dbgs() << "Post-(Thin)LTO merge bitcode embedding was requested, but "
"command line arguments are not available");
llvm::EmbedBitcodeInModule(Mod, llvm::MemoryBufferRef(),
/*EmbedBitcode*/ true,
/*EmbedMarker*/ false, CmdArgs);
}
// FIXME: Plumb the combined index into the new pass manager.
if (!Conf.OptPipeline.empty())
runNewPMCustomPasses(Conf, Mod, TM, Conf.OptPipeline, Conf.AAPipeline,
@ -531,7 +555,8 @@ Error lto::thinBackend(const Config &Conf, unsigned Task, AddStreamFn AddStream,
Module &Mod, const ModuleSummaryIndex &CombinedIndex,
const FunctionImporter::ImportMapTy &ImportList,
const GVSummaryMapTy &DefinedGlobals,
MapVector<StringRef, BitcodeModule> &ModuleMap) {
MapVector<StringRef, BitcodeModule> &ModuleMap,
const std::vector<uint8_t> *CmdArgs) {
Expected<const Target *> TOrErr = initAndLookupTarget(Conf, Mod);
if (!TOrErr)
return TOrErr.takeError();
@ -599,7 +624,8 @@ Error lto::thinBackend(const Config &Conf, unsigned Task, AddStreamFn AddStream,
return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
if (!opt(Conf, TM.get(), Task, Mod, /*IsThinLTO=*/true,
/*ExportSummary=*/nullptr, /*ImportSummary=*/&CombinedIndex))
/*ExportSummary=*/nullptr, /*ImportSummary=*/&CombinedIndex,
CmdArgs))
return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
codegen(Conf, TM.get(), AddStream, Task, Mod, CombinedIndex);

1
llvm/test/LTO/X86/Inputs/start-lib1.ll
View File

@ -4,5 +4,6 @@ target triple = "x86_64-unknown-linux-gnu"
declare void @bar()
define void @foo() {
call void @bar()
ret void
}

9
llvm/test/LTO/X86/embed-bitcode.ll
View File

@ -11,13 +11,20 @@
; RUN: llvm-lto2 run -r %t1.o,_start,px -r %t2.o,foo,px -r %t3.o,bar,px -r %t2.o,bar,lx -lto-embed-bitcode=optimized -o %t3 %t1.o %t2.o %t3.o
; RUN: llvm-readelf -S %t3.0 | FileCheck %s --check-prefix=CHECK-ELF
; RUN: llvm-objcopy --dump-section=.llvmbc=%t-embedded.bc %t3.0 /dev/null
; RUN: llvm-dis %t-embedded.bc -o - | FileCheck %s --check-prefix=CHECK-LL
; RUN: llvm-dis %t-embedded.bc -o - | FileCheck %s --check-prefixes=CHECK-LL,CHECK-OPT
; RUN: llvm-lto2 run -r %t1.o,_start,px -r %t2.o,foo,px -r %t3.o,bar,px -r %t2.o,bar,lx -lto-embed-bitcode=post-merge-pre-opt -o %t3 %t1.o %t2.o %t3.o
; RUN: llvm-readelf -S %t3.0 | FileCheck %s --check-prefix=CHECK-ELF
; RUN: llvm-objcopy --dump-section=.llvmbc=%t-embedded.bc %t3.0 /dev/null
; RUN: llvm-dis %t-embedded.bc -o - | FileCheck %s --check-prefixes=CHECK-LL,CHECK-NOOPT
; CHECK-ELF: .text PROGBITS 0000000000000000 [[#%x,OFF:]] [[#%x,SIZE:]] 00 AX 0
; CHECK-ELF-NEXT: .llvmbc PROGBITS 0000000000000000 [[#%x,OFF:]] [[#%x,SIZE:]] 00 0
; CHECK-LL: @_start
; CHECK-LL: @foo
; CHECK-OPT-NEXT: ret void
; CHECK-NOOPT-NEXT: call void @bar
; CHECK-LL: @bar
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"