forked from OSchip/llvm-project
[DebugInfo] Limit the size of DIExpressions that we will salvage up to
Fixes: https://bugs.llvm.org/show_bug.cgi?id=51841 This patch places an arbitrary limit on the size of DIExpressions that we will produce via salvaging, for performance reasons. This helps to fix a performance issue observed in the bug above, in which debug values would be salvaged hundreds of times, producing expressions with over 1000 elements and causing the compiler to hang. Limiting the size of debug values that we will produce to 128 largely fixes this issue. Reviewed By: dblaikie, jmorse Differential Revision: https://reviews.llvm.org/D110332
This commit is contained in:
Stephen Tozer
parent
b24788abd8
commit
f5ed223b0f
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@ -1733,9 +1733,11 @@ void llvm::salvageDebugInfo(Instruction &I) {
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void llvm::salvageDebugInfoForDbgValues(
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Instruction &I, ArrayRef<DbgVariableIntrinsic *> DbgUsers) {
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// This is an arbitrary chosen limit on the maximum number of values we can
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// salvage up to in a DIArgList, used for performance reasons.
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// These are arbitrary chosen limits on the maximum number of values and the
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// maximum size of a debug expression we can salvage up to, used for
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// performance reasons.
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const unsigned MaxDebugArgs = 16;
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const unsigned MaxExpressionSize = 128;
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bool Salvaged = false;
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for (auto *DII : DbgUsers) {
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@ -1772,9 +1774,10 @@ void llvm::salvageDebugInfoForDbgValues(
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break;
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DII->replaceVariableLocationOp(&I, Op0);
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if (AdditionalValues.empty()) {
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bool IsValidSalvageExpr = SalvagedExpr->getNumElements() <= MaxExpressionSize;
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if (AdditionalValues.empty() && IsValidSalvageExpr) {
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DII->setExpression(SalvagedExpr);
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} else if (isa<DbgValueInst>(DII) &&
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} else if (isa<DbgValueInst>(DII) && IsValidSalvageExpr &&
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DII->getNumVariableLocationOps() + AdditionalValues.size() <=
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MaxDebugArgs) {
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DII->addVariableLocationOps(AdditionalValues, SalvagedExpr);
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@ -0,0 +1,47 @@
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; RUN: opt %s -dce -S | FileCheck %s
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;; Tests that a DIExpression will only be salvaged up to a certain length, and
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;; will produce an undef value if an expression would need to exceed that length.
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define i32 @"?multiply@@YAHHH@Z"(i32 %a, i32 %b) !dbg !8 {
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entry:
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%add.1 = add nsw i32 %a, 5, !dbg !14
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%add.2 = add nsw i32 %a, %b, !dbg !14
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;; These expressions should salvage successfully, up to exactly 128 elements.
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; CHECK: call void @llvm.dbg.value(metadata i32 %a, metadata ![[VAR_C:[0-9]+]]
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; CHECK-NEXT: call void @llvm.dbg.value(metadata !DIArgList(i32 %a, i32 %b), metadata ![[VAR_C]]
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call void @llvm.dbg.value(metadata i32 %add.1, metadata !12, metadata !DIExpression(DW_OP_constu, 1, DW_OP_plus, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_stack_value)), !dbg !13
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call void @llvm.dbg.value(metadata i32 %add.2, metadata !12, metadata !DIExpression(DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_stack_value)), !dbg !13
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;; These expressions should be set undef, as they would salvage up to exactly 129 elements.
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; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 undef, metadata ![[VAR_C]]
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; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 undef, metadata ![[VAR_C]]
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call void @llvm.dbg.value(metadata i32 %add.1, metadata !12, metadata !DIExpression(DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_stack_value)), !dbg !13
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call void @llvm.dbg.value(metadata i32 %add.2, metadata !12, metadata !DIExpression(DW_OP_constu, 1, DW_OP_plus, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_plus_uconst, 1, DW_OP_stack_value)), !dbg !13
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%mul = mul nsw i32 %a, %b, !dbg !15
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ret i32 %mul, !dbg !15
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}
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; CHECK: ![[VAR_C]] = !DILocalVariable(name: "c"
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declare void @llvm.dbg.value(metadata, metadata, metadata)
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!3, !4, !5, !6}
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!llvm.ident = !{!7}
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!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 11.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
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!1 = !DIFile(filename: "test.cpp", directory: "/")
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!2 = !{}
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!3 = !{i32 2, !"CodeView", i32 1}
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!4 = !{i32 2, !"Debug Info Version", i32 3}
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!5 = !{i32 1, !"wchar_size", i32 2}
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!6 = !{i32 7, !"PIC Level", i32 2}
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!7 = !{!"clang version 11.0.0"}
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!8 = distinct !DISubprogram(name: "multiply", linkageName: "?multiply@@YAHHH@Z", scope: !1, file: !1, line: 1, type: !9, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
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!9 = !DISubroutineType(types: !10)
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!10 = !{!11, !11, !11}
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!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!12 = !DILocalVariable(name: "c", scope: !8, file: !1, line: 2, type: !11)
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!13 = !DILocation(line: 0, scope: !8)
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!14 = !DILocation(line: 2, scope: !8)
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!15 = !DILocation(line: 3, scope: !8)
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