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[LTO] Emit DebugLoc for dead function in optimization remarks 

Currently, the dead functions information getting from optimizations remarks does not contain debug location, but knowing where these dead functions locate could be useful for debugging or for detecting dead code.

Cause in `LTO::addRegularLTO()` we use `BitcodeModule::getLazyModule()` to read the bitcode module, when we pass Function F to `ore::NV()`, F is not materialized, so `F->getSubprogram()` returns nullptr, and there is no debug location information of dead functions in optimizations remarks.

This patch call `F->materialize()` before we pass Function F to `ore::NV()`, then debug location information will be emitted for dead functions in optimization remarks.

Reviewed By: tejohnson

Differential Revision: https://reviews.llvm.org/D109737
This commit is contained in:
Xu Mingjie 2021-09-21 12:56:50 -07:00 committed by Teresa Johnson
parent e95731cca7
commit 32ab405717
3 changed files with 27 additions and 8 deletions
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3
llvm/include/llvm/LTO/LTO.h
View File

@ -444,6 +444,9 @@ private:
// Identify symbols exported dynamically, and that therefore could be
// referenced by a shared library not visible to the linker.
DenseSet<GlobalValue::GUID> DynamicExportSymbols;
// Diagnostic optimization remarks file
std::unique_ptr<ToolOutputFile> DiagnosticOutputFile;
};
/// The resolution for a symbol. The linker must provide a SymbolResolution for

15
llvm/lib/LTO/LTO.cpp
View File

@ -857,10 +857,14 @@ Error LTO::linkRegularLTO(RegularLTOState::AddedModule Mod,
for (GlobalValue *GV : Mod.Keep) {
if (LivenessFromIndex && !ThinLTO.CombinedIndex.isGUIDLive(GV->getGUID())) {
if (Function *F = dyn_cast<Function>(GV)) {
OptimizationRemarkEmitter ORE(F, nullptr);
ORE.emit(OptimizationRemark(DEBUG_TYPE, "deadfunction", F)
<< ore::NV("Function", F)
<< " not added to the combined module ");
if (DiagnosticOutputFile) {
if (Error Err = F->materialize())
return Err;
OptimizationRemarkEmitter ORE(F, nullptr);
ORE.emit(OptimizationRemark(DEBUG_TYPE, "deadfunction", F)
<< ore::NV("Function", F)
<< " not added to the combined module ");
}
}
continue;
}
@ -1049,6 +1053,7 @@ Error LTO::runRegularLTO(AddStreamFn AddStream) {
Conf.RemarksHotnessThreshold);
if (!DiagFileOrErr)
return DiagFileOrErr.takeError();
DiagnosticOutputFile = std::move(*DiagFileOrErr);
// Finalize linking of regular LTO modules containing summaries now that
// we have computed liveness information.
@ -1137,7 +1142,7 @@ Error LTO::runRegularLTO(AddStreamFn AddStream) {
return Err;
}
return finalizeOptimizationRemarks(std::move(*DiagFileOrErr));
return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
}
static const char *libcallRoutineNames[] = {

17
llvm/test/LTO/Resolution/X86/dead-strip-fulllto.ll
View File

@ -19,9 +19,11 @@
; REMARK: Pass: lto
; REMARK-NEXT: Name: deadfunction
; REMARK-NEXT: DebugLoc: { File: test.c, Line: 4, Column: 0 }
; REMARK-NEXT: Function: dead2
; REMARK-NEXT: Args:
; REMARK-NEXT: - Function: dead2
; REMARK-NEXT: DebugLoc: { File: test.c, Line: 4, Column: 0 }
; REMARK-NEXT: - String: ' not added to the combined module '
; FULL-NOT: dead
@ -48,9 +50,18 @@ define void @live2() {
ret void
}
define void @dead2() {
define void @dead2() !dbg !7 {
ret void
}
!0 = !{i32 1, !"ThinLTO", i32 0}
!llvm.module.flags = !{ !0 }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3, !4, !5}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, isOptimized: false, emissionKind: LineTablesOnly, enums: !2)
!1 = !DIFile(filename: "test.c", directory: "/")
!2 = !{}
!3 = !{i32 2, !"Dwarf Version", i32 2}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = !{i32 1, !"ThinLTO", i32 0}
!7 = distinct !DISubprogram(name: "dead2", scope: !1, file: !1, line: 4, type: !8, isLocal: false, isDefinition: true, scopeLine: 4, isOptimized: false, unit: !0, retainedNodes: !2)
!8 = !DISubroutineType(types: !2)