3e05ab6322
Currently for thin-lto, the imported static global values (functions, variables, etc) will be promoted/renamed from e.g., foo() to foo.llvm.(). Such a renaming caused difficulties in live patching since function name is changed ([1]). It is possible that some global value names have to be promoted to avoid name collision and linker failure. But in practice, majority of name promotions can be avoided. In [2], the suggestion is that thin-lto pre-link decides whether a particular global value needs name promotion or not. If yes, later on in thinBackend() the name will be promoted. I compiled a particular linux kernel version (latest bpf-next tree) and found 1216 global values with suffix .llvm.. With this patch, the number of promoted functions is 2, 98% reduction from the original kernel build. If some native objects are not participating with LTO, name promotions have to be done to avoid potential linker issues. So the current implementation cannot be on by default. But in certain cases, e.g., linux kernel build, people can enable lld flag --lto-whole-program-visibility to reduce the number of functions like foo.llvm.(). For ThinLTOCodeGenerator.cpp which is used by llvm-lto tool and a few other rare cases, reducing the number of renaming due to promotion, is not implemented as lld flag '-lto-whole-program-visibility' is not supported in ThinLTOCodeGenerator.cpp for now. In summary, this pull request only supports llvm-lto2 style workflow. The feature is off by default. To enable the future, lld flag '-lto-whole-program-visibility' and llvm flag '-always-rename-promoted-locals=false' are needed. The link [3] has more context for the pull request discussions. [1] https://lpc.events/event/19/contributions/2212 [2] https://discourse.llvm.org/t/rfc-avoid-functions-like-foo-llvm-for-kernel-live-patch/89400 [3] https://github.com/llvm/llvm-project/pull/178587
166 lines
8.3 KiB
LLVM
166 lines
8.3 KiB
LLVM
; Test to check the callgraph in summary when there is PGO
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; RUN: opt -module-summary %s -o %t.o
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; RUN: llvm-bcanalyzer -dump %t.o | FileCheck %s
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; RUN: llvm-dis %t.o
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; RUN: cat %t.o.ll | FileCheck %s --check-prefix=DIS
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; Make sure the assembler doesn't error when parsing the summary
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; RUN: llvm-as %t.o.ll
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; Check assembled summary.
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; RUN: llvm-dis %t.o.bc -o - | FileCheck %s --check-prefix=DIS
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; RUN: opt -module-summary %p/Inputs/thinlto-function-summary-callgraph-profile-summary.ll -o %t2.o
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; RUN: llvm-lto -thinlto -o %t3 %t.o %t2.o
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; RUN: llvm-bcanalyzer -dump %t3.thinlto.bc | FileCheck %s --check-prefix=COMBINED
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; RUN: llvm-dis %t3.thinlto.bc
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; RUN: cat %t3.thinlto.ll | FileCheck %s --check-prefix=COMBINED-DIS
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; Round trip it through llvm-as
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; RUN: cat %t3.thinlto.ll | llvm-as -o - | llvm-dis -o - | FileCheck %s --check-prefix=COMBINED-DIS
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; Make sure the assembler doesn't error when parsing the combined summary
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; RUN: llvm-as %t3.thinlto.ll -o %t3.thinlto.o
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; Check assembled combined summary.
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; RUN: llvm-dis %t3.thinlto.o -o - | FileCheck %s --check-prefix=COMBINED-DIS
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; CHECK: <SOURCE_FILENAME
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; "hot_function"
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; CHECK-NEXT: <FUNCTION op0=0 op1=12
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; "hot1"
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; CHECK-NEXT: <FUNCTION op0=12 op1=4
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; "hot2"
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; CHECK-NEXT: <FUNCTION op0=16 op1=4
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; "hot3"
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; CHECK-NEXT: <FUNCTION op0=20 op1=4
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; "hot4"
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; CHECK-NEXT: <FUNCTION op0=24 op1=4
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; "cold"
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; CHECK-NEXT: <FUNCTION op0=28 op1=4
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; "none1"
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; CHECK-NEXT: <FUNCTION op0=32 op1=5
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; "none2"
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; CHECK-NEXT: <FUNCTION op0=37 op1=5
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; "none3"
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; CHECK-NEXT: <FUNCTION op0=42 op1=5
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; CHECK-LABEL: <GLOBALVAL_SUMMARY_BLOCK
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; CHECK-NEXT: <VERSION
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; CHECK-NEXT: <FLAGS
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; CHECK-NEXT: <VALUE_GUID {{.*}} op0=25 op1=0 op2=123/>
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; op4=hot1 op6=cold op8=hot2 op10=hot4 op12=none1 op14=hot3 op16=none2 op18=none3 op20=123
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; CHECK-NEXT: <PERMODULE_PROFILE {{.*}} op7=1 op8=3 op9=5 op10=1 op11=2 op12=3 op13=4 op14=1 op15=6 op16=2 op17=3 op18=3 op19=7 op20=2 op21=8 op22=2 op23=25 op24=4/>
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; CHECK-NEXT: </GLOBALVAL_SUMMARY_BLOCK>
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; CHECK: <STRTAB_BLOCK
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; CHECK-NEXT: blob data = 'hot_functionhot1hot2hot3hot4coldnone1none2none3{{.*}}'
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; COMBINED: <GLOBALVAL_SUMMARY_BLOCK
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; COMBINED-NEXT: <VERSION
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; COMBINED-NEXT: <FLAGS
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; COMBINED-NEXT: <VALUE_GUID
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; COMBINED-NEXT: <VALUE_GUID
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; COMBINED-NEXT: <VALUE_GUID
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; COMBINED-NEXT: <VALUE_GUID
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; COMBINED-NEXT: <VALUE_GUID
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; COMBINED-NEXT: <VALUE_GUID
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; COMBINED-NEXT: <VALUE_GUID
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; COMBINED-NEXT: <VALUE_GUID
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; COMBINED-NEXT: <COMBINED_PROFILE abbrevid=
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; COMBINED-NEXT: <COMBINED_PROFILE abbrevid=
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; COMBINED-NEXT: <COMBINED_PROFILE abbrevid=
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; COMBINED-NEXT: <COMBINED_PROFILE abbrevid=
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; COMBINED-NEXT: <COMBINED_PROFILE abbrevid=
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; COMBINED-NEXT: <COMBINED_PROFILE abbrevid=
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; COMBINED-NEXT: <COMBINED_PROFILE {{.*}} op9=[[HOT1:.*]] op10=3 op11=[[COLD:.*]] op12=1 op13=[[HOT2:.*]] op14=3 op15=[[NONE1:.*]] op16=2 op17=[[HOT3:.*]] op18=3 op19=[[NONE2:.*]] op20=2 op21=[[NONE3:.*]] op22=2/>
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; COMBINED-NEXT: <COMBINED_PROFILE abbrevid=
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; COMBINED-NEXT: </GLOBALVAL_SUMMARY_BLOCK>
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; ModuleID = 'thinlto-function-summary-callgraph.ll'
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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; This function have high profile count, so entry block is hot.
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define void @hot_function(i1 %a, i1 %a2) !prof !20 {
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entry:
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call void @hot1()
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br i1 %a, label %Cold, label %Hot, !prof !41
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Cold: ; 1/1000 goes here
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call void @cold()
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call void @hot2()
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call void @hot4(), !prof !15
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call void @none1()
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br label %exit
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Hot: ; 999/1000 goes here
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call void @hot2()
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call void @hot3()
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br i1 %a2, label %None1, label %None2, !prof !42
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None1: ; half goes here
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call void @none1()
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call void @none2()
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br label %exit
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None2: ; half goes here
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call void @none3()
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br label %exit
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exit:
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ret void
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}
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declare void @hot1() #1
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declare void @hot2() #1
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declare void @hot3() #1
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declare void @hot4() #1
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declare void @cold() #1
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declare void @none1() #1
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declare void @none2() #1
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declare void @none3() #1
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!41 = !{!"branch_weights", i32 1, i32 1000}
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!42 = !{!"branch_weights", i32 1, i32 1}
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!llvm.module.flags = !{!1}
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!20 = !{!"function_entry_count", i64 110, i64 123}
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!1 = !{i32 1, !"ProfileSummary", !2}
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!2 = !{!3, !4, !5, !6, !7, !8, !9, !10}
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!3 = !{!"ProfileFormat", !"InstrProf"}
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!4 = !{!"TotalCount", i64 10000}
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!5 = !{!"MaxCount", i64 10}
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!6 = !{!"MaxInternalCount", i64 1}
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!7 = !{!"MaxFunctionCount", i64 1000}
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!8 = !{!"NumCounts", i64 3}
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!9 = !{!"NumFunctions", i64 3}
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!10 = !{!"DetailedSummary", !11}
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!11 = !{!12, !13, !14}
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!12 = !{i32 10000, i64 100, i32 1}
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!13 = !{i32 999000, i64 100, i32 1}
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!14 = !{i32 999999, i64 1, i32 2}
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!15 = !{!"branch_weights", i32 100}
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; DIS: ^0 = module: (path: "{{.*}}thinlto-function-summary-callgraph-profile-summary.ll.tmp.o{{.*}}", hash: (0, 0, 0, 0, 0))
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; DIS: ^1 = gv: (guid: 123)
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; DIS: ^2 = gv: (name: "none2") ; guid = 3741006263754194003
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; DIS: ^3 = gv: (name: "hot3") ; guid = 5026609803865204483
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; DIS: ^4 = gv: (name: "hot2") ; guid = 8117347573235780485
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; DIS: ^5 = gv: (name: "hot1") ; guid = 9453975128311291976
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; DIS: ^6 = gv: (name: "cold") ; guid = 11668175513417606517
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; DIS: ^7 = gv: (name: "hot4") ; guid = 13161834114071272798
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; DIS: ^8 = gv: (name: "none3") ; guid = 16213681105727317812
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; DIS: ^9 = gv: (name: "hot_function", summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 16, calls: ((callee: ^5, hotness: hot), (callee: ^6, hotness: cold), (callee: ^4, hotness: hot), (callee: ^7, hotness: cold), (callee: ^10, hotness: none), (callee: ^3, hotness: hot), (callee: ^2, hotness: none), (callee: ^8, hotness: none), (callee: ^1, hotness: critical))))) ; guid = 17381606045411660303
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; DIS: ^10 = gv: (name: "none1") ; guid = 17712061229457633252
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; COMBINED-DIS: ^0 = module: (path: "{{.*}}thinlto-function-summary-callgraph-profile-summary.ll.tmp.o", hash: (0, 0, 0, 0, 0))
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; COMBINED-DIS: ^1 = module: (path: "{{.*}}thinlto-function-summary-callgraph-profile-summary.ll.tmp2.o", hash: (0, 0, 0, 0, 0))
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; COMBINED-DIS: ^2 = gv: (guid: 3741006263754194003, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
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; COMBINED-DIS: ^3 = gv: (guid: 5026609803865204483, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
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; COMBINED-DIS: ^4 = gv: (guid: 8117347573235780485, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
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; COMBINED-DIS: ^5 = gv: (guid: 9453975128311291976, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
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; COMBINED-DIS: ^6 = gv: (guid: 11668175513417606517, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
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; COMBINED-DIS: ^7 = gv: (guid: 16213681105727317812, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
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; COMBINED-DIS: ^8 = gv: (guid: 17381606045411660303, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 16, calls: ((callee: ^5, hotness: hot), (callee: ^6, hotness: cold), (callee: ^4, hotness: hot), (callee: ^9, hotness: none), (callee: ^3, hotness: hot), (callee: ^2, hotness: none), (callee: ^7, hotness: none)))))
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; COMBINED-DIS: ^9 = gv: (guid: 17712061229457633252, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
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