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)
75 lines
3.6 KiB
LLVM
75 lines
3.6 KiB
LLVM
; Promote at most one function and annotate at most one vtable.
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; As a result, only one value (of each relevant kind) shows up in the function
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; summary.
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; RUN: opt -module-summary -icp-max-num-vtables=1 -icp-max-prom=1 %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 -o - | llvm-dis -o - | FileCheck %s --check-prefix=DIS
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; CHECK: <GLOBALVAL_SUMMARY_BLOCK
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; CHECK-NEXT: <VERSION op0=9/>
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; CHECK-NEXT: <FLAGS op0=0/>
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; The `VALUE_GUID` below represents the "_ZTV4Base" referenced by the instruction
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; that loads vtable pointers.
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; CHECK-NEXT: <VALUE_GUID op0=21 op1=1960855528937986108/>
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; The `VALUE_GUID` below represents the "_ZN4Base4funcEv" referenced by the
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; indirect call instruction.
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; CHECK-NEXT: <VALUE_GUID op0=20 op1=5459407273543877811/>
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; NOTE vtables and functions from Derived class is dropped because
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; `-icp-max-num-vtables` and `-icp-max-prom` are both set to one.
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; <PERMODULE_PROFILE> has the format [valueid, flags, instcount, funcflags,
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; numrefs, rorefcnt, worefcnt,
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; m x valueid,
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; n x (valueid, hotness+tailcall)]
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; CHECK-NEXT: <PERMODULE_PROFILE abbrevid=4 op0=0 op1=0 op2=4 op3=256 op4=1 op5=1 op6=0 op7=21 op8=20 op9=3/>
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; CHECK-NEXT: </GLOBALVAL_SUMMARY_BLOCK>
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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 has one BB and an entry count of 150, so the BB is hot according to
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; ProfileSummary and reflected so in the bitcode (see llvm-dis output).
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define i32 @_Z4testP4Base(ptr %0) !prof !15 {
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%2 = load ptr, ptr %0, !prof !16
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%3 = load ptr, ptr %2
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%4 = tail call i32 %3(ptr %0), !prof !17
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ret i32 %4
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}
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!llvm.module.flags = !{!1}
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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 200}
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!6 = !{!"MaxInternalCount", i64 200}
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!7 = !{!"MaxFunctionCount", i64 200}
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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 990000, i64 100, i32 1}
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!14 = !{i32 999999, i64 1, i32 2}
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!15 = !{!"function_entry_count", i32 150}
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; 1960855528937986108 is the MD5 hash of _ZTV4Base, and
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; 13870436605473471591 is the MD5 hash of _ZTV7Derived
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!16 = !{!"VP", i32 2, i64 150, i64 1960855528937986108, i64 100, i64 13870436605473471591, i64 50}
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; 5459407273543877811 is the MD5 hash of _ZN4Base4funcEv, and
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; 6174874150489409711 is the MD5 hash of _ZN7Derived4funcEv
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!17 = !{!"VP", i32 0, i64 150, i64 5459407273543877811, i64 100, i64 6174874150489409711, i64 50}
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; ModuleSummaryIndex stores <guid, global-value summary> map in std::map; so
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; global value summares are printed out in the order that gv's guid increases.
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; DIS: ^0 = module: (path: "{{.*}}", hash: (0, 0, 0, 0, 0))
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; DIS: ^1 = gv: (guid: 1960855528937986108)
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; DIS: ^2 = gv: (guid: 5459407273543877811)
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; DIS: ^3 = gv: (name: "_Z4testP4Base", summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0, importType: definition), insts: 4, funcFlags: (readNone: 0, readOnly: 0, noRecurse: 0, returnDoesNotAlias: 0, noInline: 0, alwaysInline: 0, noUnwind: 0, mayThrow: 0, hasUnknownCall: 1, mustBeUnreachable: 0), calls: ((callee: ^2, hotness: hot)), refs: (readonly ^1)))) ; guid = 15857150948103218965
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; DIS: ^4 = blockcount: 0
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