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llvm-project/llvm/test/Assembler/thinlto-summary.ll
yonghong-song 3e05ab6322
[ThinLTO] Reduce the number of renaming due to promotions (#183793) 
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
2026-02-28 12:44:25 -08:00

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; Test summary parsing (tests all types/fields in various combinations).
; RUN: llvm-as %s -o - | llvm-dis -o - | FileCheck %s
; ModuleID = 'thinlto-summary.thinlto.bc'
^0 = module: (path: "thinlto-summary1.o", hash: (1369602428, 2747878711, 259090915, 2507395659, 1141468049))
^1 = module: (path: "thinlto-summary2.o", hash: (2998369023, 4283347029, 1195487472, 2757298015, 1852134156))
; Check a function that makes several calls with various profile hotness, and a
; reference (also tests forward references to function and variables in calls
; and refs).
^2 = gv: (guid: 1, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 10, calls: ((callee: ^15, hotness: hot), (callee: ^17, hotness: cold), (callee: ^16, hotness: none, tail: 1)), refs: (writeonly ^14, readonly ^13, ^11))))
;; relbf is deprecated, but we support reading old files.
; Function with a call that has relative block frequency instead of profile
; hotness.
^3 = gv: (guid: 2, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 10, calls: ((callee: ^15, relbf: 256, tail: 1)))))
; Summaries with different linkage types.
^4 = gv: (guid: 3, summaries: (function: (module: ^0, flags: (linkage: internal, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1, importType: definition, noRenameOnPromotion: 0), insts: 1)))
; Make this one an alias with a forward reference to aliasee.
^5 = gv: (guid: 4, summaries: (alias: (module: ^0, flags: (linkage: private, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1, importType: definition, noRenameOnPromotion: 0), aliasee: ^14)))
^6 = gv: (guid: 5, summaries: (function: (module: ^0, flags: (linkage: available_externally, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 1)))
^7 = gv: (guid: 6, summaries: (function: (module: ^0, flags: (linkage: linkonce, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 1)))
^8 = gv: (guid: 7, summaries: (function: (module: ^0, flags: (linkage: linkonce_odr, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 1)))
^9 = gv: (guid: 8, summaries: (function: (module: ^0, flags: (linkage: weak_odr, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 1, importType: definition, noRenameOnPromotion: 0), insts: 1)))
^10 = gv: (guid: 9, summaries: (function: (module: ^0, flags: (linkage: weak, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 1)))
^11 = gv: (guid: 10, summaries: (variable: (module: ^0, flags: (linkage: common, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), varFlags: (readonly: 0))))
; Test appending globel variable with reference (tests backward reference on
; refs).
^12 = gv: (guid: 11, summaries: (variable: (module: ^0, flags: (linkage: appending, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), varFlags: (readonly: 0), refs: (^4))))
; Test a referenced global variable.
^13 = gv: (guid: 12, summaries: (variable: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), varFlags: (readonly: 1))))
; Test a dsoLocal variable.
^14 = gv: (guid: 13, summaries: (variable: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1), varFlags: (writeonly: 0))))
; Functions with various flag combinations (notEligibleToImport, Live,
; combinations of optional function flags).
^15 = gv: (guid: 14, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 1, live: 1, dsoLocal: 0), insts: 1, funcFlags: (noInline: 1, mustBeUnreachable: 0))))
^16 = gv: (guid: 15, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 1, funcFlags: (readNone: 1, noRecurse: 1, alwaysInline: 1, noUnwind : 1, mayThrow : 1, hasUnknownCall : 1, mustBeUnreachable: 0))))
; This one also tests backwards reference in calls.
^17 = gv: (guid: 16, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 1, funcFlags: (readOnly: 1, returnDoesNotAlias: 1, mustBeUnreachable: 1), calls: ((callee: ^15)))))
; Alias summary with backwards reference to aliasee.
^18 = gv: (guid: 17, summaries: (alias: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1), aliasee: ^14)))
; Test all types of TypeIdInfo on function summaries.
^19 = gv: (guid: 18, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 4, typeIdInfo: (typeTests: (^27, ^29)))))
^20 = gv: (guid: 19, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 8, typeIdInfo: (typeTestAssumeVCalls: (vFuncId: (^30, offset: 16))))))
^21 = gv: (guid: 20, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 5, typeIdInfo: (typeCheckedLoadVCalls: (vFuncId: (^28, offset: 16))))))
^22 = gv: (guid: 21, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 15, typeIdInfo: (typeTestAssumeConstVCalls: ((vFuncId: (^30, offset: 16), args: (42)), (vFuncId: (^30, offset: 24)))))))
^23 = gv: (guid: 22, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 5, typeIdInfo: (typeCheckedLoadConstVCalls: ((vFuncId: (^31, offset: 16), args: (42)))))))
; Function summary with an import type of declaration
^24 = gv: (guid: 23, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, importType: declaration, noRenameOnPromotion: 0), insts: 5)))
; Alias summary with null aliasee.
^25 = gv: (guid: 24, summaries: (alias: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1), aliasee: null)))
; GUID that are 64-bit
^26 = gv: (guid: 9123456789101112131, summaries: (function: (module: ^0, flags: (linkage: internal, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1, importType: definition, noRenameOnPromotion: 0), insts: 1)))
; Test TypeId summaries:
^27 = typeid: (name: "_ZTS1C", summary: (typeTestRes: (kind: single, sizeM1BitWidth: 0)))
; Test TypeId with other optional fields (alignLog2/sizeM1/bitMask/inlineBits)
^28 = typeid: (name: "_ZTS1B", summary: (typeTestRes: (kind: inline, sizeM1BitWidth: 0, alignLog2: 1, sizeM1: 2, bitMask: 3, inlineBits: 4)))
; Test the AllOnes resolution, and all kinds of WholeProgramDevirtResolution
; types, including all optional resolution by argument kinds.
^29 = typeid: (name: "_ZTS1A", summary: (typeTestRes: (kind: allOnes, sizeM1BitWidth: 7), wpdResolutions: ((offset: 0, wpdRes: (kind: branchFunnel)), (offset: 8, wpdRes: (kind: singleImpl, singleImplName: "_ZN1A1nEi")), (offset: 16, wpdRes: (kind: indir, resByArg: (args: (1, 2), byArg: (kind: indir, byte: 2, bit: 3), args: (3), byArg: (kind: uniformRetVal, info: 1), args: (4), byArg: (kind: uniqueRetVal, info: 1), args: (5), byArg: (kind: virtualConstProp)))))))
; Test the other kinds of type test resoultions
^30 = typeid: (name: "_ZTS1D", summary: (typeTestRes: (kind: byteArray, sizeM1BitWidth: 0)))
^31 = typeid: (name: "_ZTS1E", summary: (typeTestRes: (kind: unsat, sizeM1BitWidth: 0)))
^32 = flags: 8
^33 = blockcount: 1888
; Make sure we get back from llvm-dis essentially what we put in via llvm-as.
; CHECK: ^0 = module: (path: "thinlto-summary1.o", hash: (1369602428, 2747878711, 259090915, 2507395659, 1141468049))
; CHECK: ^1 = module: (path: "thinlto-summary2.o", hash: (2998369023, 4283347029, 1195487472, 2757298015, 1852134156))
; CHECK: ^2 = gv: (guid: 1, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 10, calls: ((callee: ^15, hotness: hot), (callee: ^17, hotness: cold), (callee: ^16, hotness: none, tail: 1)), refs: (^11, readonly ^13, writeonly ^14))))
;; relbf is not emitted since this is a combined summary, and that is only
;; emitted for per-module summaries. Additionally, it is now deprecated.
; CHECK: ^3 = gv: (guid: 2, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 10, calls: ((callee: ^15, tail: 1)))))
; CHECK: ^4 = gv: (guid: 3, summaries: (function: (module: ^0, flags: (linkage: internal, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
; CHECK: ^5 = gv: (guid: 4, summaries: (alias: (module: ^0, flags: (linkage: private, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), aliasee: ^14)))
; CHECK: ^6 = gv: (guid: 5, summaries: (function: (module: ^0, flags: (linkage: available_externally, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
; CHECK: ^7 = gv: (guid: 6, summaries: (function: (module: ^0, flags: (linkage: linkonce, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
; CHECK: ^8 = gv: (guid: 7, summaries: (function: (module: ^0, flags: (linkage: linkonce_odr, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
; CHECK: ^9 = gv: (guid: 8, summaries: (function: (module: ^0, flags: (linkage: weak_odr, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 1, importType: definition, noRenameOnPromotion: 0), insts: 1)))
; CHECK: ^10 = gv: (guid: 9, summaries: (function: (module: ^0, flags: (linkage: weak, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
; CHECK: ^11 = gv: (guid: 10, summaries: (variable: (module: ^0, flags: (linkage: common, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), varFlags: (readonly: 0, writeonly: 0, constant: 0))))
; CHECK: ^12 = gv: (guid: 11, summaries: (variable: (module: ^0, flags: (linkage: appending, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), varFlags: (readonly: 0, writeonly: 0, constant: 0), refs: (^4))))
; CHECK: ^13 = gv: (guid: 12, summaries: (variable: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), varFlags: (readonly: 1, writeonly: 0, constant: 0))))
; CHECK: ^14 = gv: (guid: 13, summaries: (variable: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), varFlags: (readonly: 0, writeonly: 0, constant: 0))))
; CHECK: ^15 = gv: (guid: 14, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 1, live: 1, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1, funcFlags: (readNone: 0, readOnly: 0, noRecurse: 0, returnDoesNotAlias: 0, noInline: 1, alwaysInline: 0, noUnwind: 0, mayThrow: 0, hasUnknownCall: 0, mustBeUnreachable: 0))))
; CHECK: ^16 = gv: (guid: 15, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1, funcFlags: (readNone: 1, readOnly: 0, noRecurse: 1, returnDoesNotAlias: 0, noInline: 0, alwaysInline: 1, noUnwind: 1, mayThrow: 1, hasUnknownCall: 1, mustBeUnreachable: 0))))
; CHECK: ^17 = gv: (guid: 16, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1, funcFlags: (readNone: 0, readOnly: 1, noRecurse: 0, returnDoesNotAlias: 1, noInline: 0, alwaysInline: 0, noUnwind: 0, mayThrow: 0, hasUnknownCall: 0, mustBeUnreachable: 1), calls: ((callee: ^15)))))
; CHECK: ^18 = gv: (guid: 17, summaries: (alias: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), aliasee: ^14)))
; CHECK: ^19 = gv: (guid: 18, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 4, typeIdInfo: (typeTests: (^27, ^29)))))
; CHECK: ^20 = gv: (guid: 19, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 8, typeIdInfo: (typeTestAssumeVCalls: (vFuncId: (^30, offset: 16))))))
; CHECK: ^21 = gv: (guid: 20, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 5, typeIdInfo: (typeCheckedLoadVCalls: (vFuncId: (^28, offset: 16))))))
; CHECK: ^22 = gv: (guid: 21, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 15, typeIdInfo: (typeTestAssumeConstVCalls: ((vFuncId: (^30, offset: 16), args: (42)), (vFuncId: (^30, offset: 24)))))))
; CHECK: ^23 = gv: (guid: 22, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 5, typeIdInfo: (typeCheckedLoadConstVCalls: ((vFuncId: (^31, offset: 16), args: (42)))))))
; CHECK: ^24 = gv: (guid: 23, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: declaration, noRenameOnPromotion: 0), insts: 5)))
; CHECK: ^25 = gv: (guid: 24, summaries: (alias: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), aliasee: null)))
; CHECK: ^26 = gv: (guid: 9123456789101112131, summaries: (function: (module: ^0, flags: (linkage: internal, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 1, canAutoHide: 0, importType: definition, noRenameOnPromotion: 0), insts: 1)))
; CHECK: ^27 = typeid: (name: "_ZTS1C", summary: (typeTestRes: (kind: single, sizeM1BitWidth: 0))) ; guid = 1884921850105019584
; CHECK: ^28 = typeid: (name: "_ZTS1B", summary: (typeTestRes: (kind: inline, sizeM1BitWidth: 0, alignLog2: 1, sizeM1: 2, bitMask: 3, inlineBits: 4))) ; guid = 6203814149063363976
; CHECK: ^29 = typeid: (name: "_ZTS1A", summary: (typeTestRes: (kind: allOnes, sizeM1BitWidth: 7), wpdResolutions: ((offset: 0, wpdRes: (kind: branchFunnel)), (offset: 8, wpdRes: (kind: singleImpl, singleImplName: "_ZN1A1nEi")), (offset: 16, wpdRes: (kind: indir, resByArg: (args: (1, 2), byArg: (kind: indir, byte: 2, bit: 3), args: (3), byArg: (kind: uniformRetVal, info: 1), args: (4), byArg: (kind: uniqueRetVal, info: 1), args: (5), byArg: (kind: virtualConstProp))))))) ; guid = 7004155349499253778
; CHECK: ^30 = typeid: (name: "_ZTS1D", summary: (typeTestRes: (kind: byteArray, sizeM1BitWidth: 0))) ; guid = 9614786172484273522
; CHECK: ^31 = typeid: (name: "_ZTS1E", summary: (typeTestRes: (kind: unsat, sizeM1BitWidth: 0))) ; guid = 17437243864166745132
; CHECK: ^32 = flags: 8
; CHECK: ^33 = blockcount: 1888
; Make sure parsing of a non-summary entry containing a ":" does not fail
; after summary parsing, which handles colons differently.
!0 = !DIFile(filename: "thinlto-summary.ll", directory: "", source: "")
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