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)
44 lines
1.7 KiB
LLVM
44 lines
1.7 KiB
LLVM
; Test to check the callgraph in summary
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; RUN: opt -write-relbf-to-summary -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 -o - %t.o | FileCheck %s --check-prefix=DIS
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; Round trip it through llvm-as
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; RUN: llvm-dis -o - %t.o | llvm-as -write-relbf-to-summary -o - | llvm-dis -o - | FileCheck %s --check-prefix=DIS
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; CHECK: <SOURCE_FILENAME
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; CHECK-NEXT: <GLOBALVAR
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; CHECK-NEXT: <FUNCTION
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; "func"
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; CHECK-NEXT: <FUNCTION op0=17 op1=4
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; CHECK: <GLOBALVAL_SUMMARY_BLOCK
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; CHECK-NEXT: <VERSION
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; CHECK-NEXT: <FLAGS
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; See if the call to func is registered.
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; CHECK-NEXT: <PERMODULE_RELBF {{.*}} op4=1 {{.*}} op9=256
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; CHECK-NEXT: </GLOBALVAL_SUMMARY_BLOCK>
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; CHECK: <STRTAB_BLOCK
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; CHECK-NEXT: blob data = 'undefinedglobmainfunc{{.*}}'
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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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; Function Attrs: nounwind uwtable
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define i32 @main() #0 {
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entry:
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call void (...) @func()
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%u = load i32, i32* @undefinedglob
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ret i32 %u
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}
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declare void @func(...) #1
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@undefinedglob = external global i32
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; OLD: Index {{.*}} contains 1 nodes (1 functions, 0 alias, 0 globals) and 1 edges (0 refs and 1 calls)
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; DIS: ^0 = module: (path: "{{.*}}", hash: (0, 0, 0, 0, 0))
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; DIS: ^1 = gv: (name: "func") ; guid = 7289175272376759421
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; DIS: ^2 = gv: (name: "main", summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition), insts: 3, calls: ((callee: ^1, relbf: 256)), refs: (readonly ^3)))) ; guid = 15822663052811949562
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; DIS: ^3 = gv: (name: "undefinedglob") ; guid = 18036901804029949403
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