dda73336ad
The motivating use case is to support import the function declaration across modules to construct call graph edges for indirect calls [1] when importing the function definition costs too much compile time (e.g., the function is too large has no `noinline` attribute). 1. Currently, when the compiled IR module doesn't have a function definition but its postlink combined summary contains the function summary or a global alias summary with this function as aliasee, the function definition will be imported from source module by IRMover. The implementation is in FunctionImporter::importFunctions [2] 2. In order for FunctionImporter to import a declaration of a function, both function summary and alias summary need to carry the def / decl state. Specifically, all existing summary fields doesn't differ across import modules, but the def / decl state of is decided by `<ImportModule, Function>`. This change encodes the def/decl state in `GlobalValueSummary::GVFlags`. In the subsequent changes 1. The indexing step `computeImportForModule` [3] will compute the set of definitions and the set of declarations for each module, and passing on the information to bitcode writer. 2. Bitcode writer will look up the def/decl state and sets the state when it writes out the flag value. This is demonstrated in https://github.com/llvm/llvm-project/pull/87600 3. Function importer will read the def/decl state when reading the combined summary to figure out two sets of global values, and IRMover will be updated to import the declaration (aka linkGlobalValuePrototype [4]) into the destination module. - The next change is https://github.com/llvm/llvm-project/pull/87600 [1] mentioned in rfc https://discourse.llvm.org/t/rfc-for-better-call-graph-sort-build-a-more-complete-call-graph-by-adding-more-indirect-call-edges/74029#support-cross-module-function-declaration-import-5 [2]3b337242ee/llvm/lib/Transforms/IPO/FunctionImport.cpp (L1608-L1764)[3]3b337242ee/llvm/lib/Transforms/IPO/FunctionImport.cpp (L856)[4]3b337242ee/llvm/lib/Linker/IRMover.cpp (L605)
40 lines
2.2 KiB
LLVM
40 lines
2.2 KiB
LLVM
; Test summary parsing of index-based WPD related summary fields
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; RUN: llvm-as %s -o - | llvm-dis -o %t.ll
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; RUN: grep "^\^" %s >%t2
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; RUN: grep "^\^" %t.ll >%t3
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; Expect that the summary information is the same after round-trip through
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; llvm-as and llvm-dis.
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; RUN: diff -b %t2 %t3
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source_filename = "thinlto-vtable-summary.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-grtev4-linux-gnu"
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%struct.A = type { ptr }
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%struct.B = type { %struct.A }
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%struct.C = type { %struct.A }
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@_ZTV1B = constant { [4 x ptr] } { [4 x ptr] [ptr null, ptr undef, ptr @_ZN1B1fEi, ptr @_ZN1A1nEi] }, !type !0, !type !1
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@_ZTV1C = constant { [4 x ptr] } { [4 x ptr] [ptr null, ptr undef, ptr @_ZN1C1fEi, ptr @_ZN1A1nEi] }, !type !0, !type !2
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declare i32 @_ZN1B1fEi(ptr, i32)
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declare i32 @_ZN1A1nEi(ptr, i32)
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declare i32 @_ZN1C1fEi(ptr, i32)
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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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^0 = module: (path: "<stdin>", hash: (0, 0, 0, 0, 0))
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^1 = gv: (name: "_ZN1A1nEi") ; guid = 1621563287929432257
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^2 = gv: (name: "_ZTV1B", summaries: (variable: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition), varFlags: (readonly: 0, writeonly: 0, constant: 0, vcall_visibility: 0), vTableFuncs: ((virtFunc: ^3, offset: 16), (virtFunc: ^1, offset: 24)), refs: (^3, ^1)))) ; guid = 5283576821522790367
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^3 = gv: (name: "_ZN1B1fEi") ; guid = 7162046368816414394
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^4 = gv: (name: "_ZTV1C", summaries: (variable: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition), varFlags: (readonly: 0, writeonly: 0, constant: 0, vcall_visibility: 0), vTableFuncs: ((virtFunc: ^5, offset: 16), (virtFunc: ^1, offset: 24)), refs: (^1, ^5)))) ; guid = 13624023785555846296
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^5 = gv: (name: "_ZN1C1fEi") ; guid = 14876272565662207556
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^6 = typeidCompatibleVTable: (name: "_ZTS1A", summary: ((offset: 16, ^2), (offset: 16, ^4))) ; guid = 7004155349499253778
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^7 = typeidCompatibleVTable: (name: "_ZTS1B", summary: ((offset: 16, ^2))) ; guid = 6203814149063363976
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^8 = typeidCompatibleVTable: (name: "_ZTS1C", summary: ((offset: 16, ^4))) ; guid = 1884921850105019584
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^9 = blockcount: 0
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