c27ab339ad
This restores commit ab1b4810b55279bcf6fdd87be74a403440be3991 which was reverted in 01b9deba76a950f04574b656c7c31ae389104f2d, with a fix for the issue it caused. We should use a temporary BitstreamCursor when loading the global decl attachment records so that the abbrev ids held in the lazy loading IndexCursor are not clobbered. Enhanced the test so that the issue is exposed there. Original description: When performing ThinLTO importing, the metadata loader attempts to lazy load, by building an index. However, module level global decl attachment metadata was being parsed early while building the index, since the associated (module level) global values aren't materialized on demand. This results in the creation of forward reference temporary metadatas, which are expensive. Normally, these module level global values don't have much attached metadata. However, in the case of -fwhole-program-vtables (e.g. for whole program devirtualization), the vtables may have many attached type metadatas. This was resulting in very slow performance when performing ThinLTO importing with the default lazy loading. This patch restructures the handling of these global decl attachment records, delaying their parsing until after the lazy loading index has been built. Then the parser can use the interface that loads from the index, which resolves forward references immediately instead of creating expensive temporaries. For one ThinLTO backend that imports from modules containing huge numbers of vtables and associated types, I measured the following compile times for the metadata materialization during function importing, rounded to nearest second: No -fwhole-program-vtables: Lazy loading on (head): 1s Lazy loading off (head): 3s Lazy loading on (patch): 1s With -fwhole-program-vtables: Lazy loading on (head): 440s Lazy loading off (head): 4s Lazy loading on (patch): 2s Differential Revision: https://reviews.llvm.org/D87970
76 lines
3.1 KiB
LLVM
76 lines
3.1 KiB
LLVM
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-grtev4-linux-gnu"
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%struct.A = type { i32 (...)** }
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%struct.B = type { %struct.A }
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%struct.C = type { %struct.A }
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%struct.D = type { i32 (...)** }
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%struct.E = type { i32 (...)** }
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@_ZTV1B = constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* undef, i8* bitcast (i32 (%struct.B*, i32)* @_ZN1B1fEi to i8*), i8* bitcast (i32 (%struct.A*, i32)* @_ZN1A1nEi to i8*)] }, !type !0, !type !1
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@_ZTV1C = constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* undef, i8* bitcast (i32 (%struct.C*, i32)* @_ZN1C1fEi to i8*), i8* bitcast (i32 (%struct.A*, i32)* @_ZN1A1nEi to i8*)] }, !type !0, !type !2
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@_ZTV1D = linkonce_odr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* undef, i8* bitcast (i32 (%struct.D*, i32)* @_ZN1D1mEi to i8*)] }, !type !3
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@_ZTV1E = constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* undef, i8* bitcast (i32 (%struct.E*, i32)* @_ZN1E1mEi to i8*)] }, !type !4
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define i32 @_ZN1B1fEi(%struct.B* %this, i32 %a) #0 {
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ret i32 0
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}
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define internal i32 @_ZN1A1nEi(%struct.A* %this, i32 %a) #0 {
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ret i32 0
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}
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define i32 @_ZN1C1fEi(%struct.C* %this, i32 %a) #0 {
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ret i32 0
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}
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define linkonce_odr i32 @_ZN1D1mEi(%struct.D* %this, i32 %a) #0 {
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ret i32 0
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}
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define internal i32 @_ZN1E1mEi(%struct.E* %this, i32 %a) #0 {
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ret i32 0, !dbg !12
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}
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define i32 @test2(%struct.E* %obj, i32 %a) {
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entry:
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%0 = bitcast %struct.E* %obj to i8***, !dbg !12
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%vtable2 = load i8**, i8*** %0
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%1 = bitcast i8** %vtable2 to i8*
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%p2 = call i1 @llvm.type.test(i8* %1, metadata !"_ZTS1E")
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call void @llvm.assume(i1 %p2)
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%2 = bitcast i8** %vtable2 to i32 (%struct.E*, i32)**
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%fptr33 = load i32 (%struct.E*, i32)*, i32 (%struct.E*, i32)** %2, align 8
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%call4 = tail call i32 %fptr33(%struct.E* nonnull %obj, i32 %a)
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ret i32 %call4
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}
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attributes #0 = { noinline optnone }
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declare i1 @llvm.type.test(i8*, metadata)
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declare void @llvm.assume(i1)
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!llvm.dbg.cu = !{!5}
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!llvm.module.flags = !{!13, !14, !15}
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!0 = !{i64 16, !"_ZTS1A"}
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!1 = !{i64 16, !"_ZTS1B"}
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!2 = !{i64 16, !"_ZTS1C"}
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!3 = !{i64 16, !"_ZTS1D"}
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!4 = !{i64 16, !"_ZTS1E"}
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!5 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !6, producer: "clang version 12.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !7, splitDebugInlining: false, nameTableKind: None)
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!6 = !DIFile(filename: "test.cc", directory: "/tmp")
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!7 = !{}
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!8 = distinct !DISubprogram(name: "bar", linkageName: "_Z5barv", scope: !6, file: !6, line: 1, type: !9, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !7)
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!9 = !DISubroutineType(types: !10)
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!10 = !{!11}
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!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!12 = !DILocation(line: 2, column: 3, scope: !8, inlinedAt: !16)
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!13 = !{i32 7, !"Dwarf Version", i32 4}
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!14 = !{i32 2, !"Debug Info Version", i32 3}
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!15 = !{i32 1, !"wchar_size", i32 4}
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!16 = !DILocation(line: 1, column: 1, scope: !17)
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!17 = distinct !DISubprogram(name: "foo", linkageName: "_Z5foov", scope: !6, file: !6, line: 1, type: !9, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !7)
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