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[StripDeadDebugInfo] Drop dead CUs entirely 

Summary:
Prior to this while it would delete the dead DIGlobalVariables, it would
leave dead DICompileUnits and everything referenced therefrom. For a bit
bitcode file with thousands of compile units those dead nodes easily
outnumbered the real ones. Clean that up.

Reviewed By: aprantl
Differential Revision: https://reviews.llvm.org/D31720

llvm-svn: 299692
This commit is contained in:
Keno Fischer 2017-04-06 19:26:22 +00:00
parent b122ed9181
commit bacc64b5fa
2 changed files with 34 additions and 2 deletions
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25
llvm/lib/Transforms/IPO/StripSymbols.cpp
View File

@ -323,6 +323,15 @@ bool StripDeadDebugInfo::runOnModule(Module &M) {
LiveGVs.insert(GVE);
}
std::set<DICompileUnit *> LiveCUs;
// Any CU referenced from a function is live.
for (Function &F : M.functions()) {
DISubprogram *SP = F.getSubprogram();
if (SP && SP->getUnit())
LiveCUs.insert(SP->getUnit());
}
bool HasDeadCUs = false;
for (DICompileUnit *DIC : F.compile_units()) {
// Create our live global variable list.
bool GlobalVariableChange = false;
@ -341,6 +350,11 @@ bool StripDeadDebugInfo::runOnModule(Module &M) {
GlobalVariableChange = true;
}
if (!LiveGlobalVariables.empty())
LiveCUs.insert(DIC);
else if (!LiveCUs.count(DIC))
HasDeadCUs = true;
// If we found dead global variables, replace the current global
// variable list with our new live global variable list.
if (GlobalVariableChange) {
@ -352,5 +366,16 @@ bool StripDeadDebugInfo::runOnModule(Module &M) {
LiveGlobalVariables.clear();
}
if (HasDeadCUs) {
// Delete the old node and replace it with a new one
NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.dbg.cu");
NMD->clearOperands();
if (!LiveCUs.empty()) {
for (DICompileUnit *CU : LiveCUs)
NMD->addOperand(CU);
}
Changed = true;
}
return Changed;
}

11
llvm/test/Transforms/StripSymbols/strip-dead-debug-info.ll
View File

@ -3,6 +3,9 @@
; CHECK: ModuleID = '{{.*}}'
; CHECK-NOT: "bar"
; CHECK-NOT: "abcd"
; CHECK-NOT: "GCC"
; CHECK: "Globals"
; CHECK: "abcd2"
source_filename = "test/Transforms/StripSymbols/strip-dead-debug-info.ll"
@ -29,7 +32,7 @@ attributes #0 = { nounwind readnone }
attributes #1 = { nounwind readnone ssp }
attributes #2 = { nounwind readonly ssp }
!llvm.dbg.cu = !{!4}
!llvm.dbg.cu = !{!4, !23, !24}
!llvm.module.flags = !{!9}
!0 = !DIGlobalVariableExpression(var: !1)
@ -55,4 +58,8 @@ attributes #2 = { nounwind readonly ssp }
!20 = !DILocation(line: 7, scope: !15)
!21 = !DILocation(line: 10, scope: !22)
!22 = distinct !DILexicalBlock(scope: !15, file: !2, line: 7)
!23 = distinct !DICompileUnit(language: DW_LANG_C89, file: !2, producer: "GCC", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !5, retainedTypes: !5, globals: !5)
!24 = distinct !DICompileUnit(language: DW_LANG_C89, file: !2, producer: "Globals", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !5, retainedTypes: !5, globals: !25)
!25 = !{!26}
!26 = !DIGlobalVariableExpression(var: !27, expr: !DIExpression(DW_OP_constu, 0, DW_OP_stack_value))
!27 = !DIGlobalVariable(name: "abcd2", scope: !2, file: !2, line: 2, type: !3, isLocal: true, isDefinition: true)