[all-commits] [llvm/llvm-project] dda733: [ThinLTO]Record import type in GlobalValueSummary:...

[Mingming Liu via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: dda73336ad22bd0b5ecda17040c50fb10fcbe5fb
      https://github.com/llvm/llvm-project/commit/dda73336ad22bd0b5ecda17040c50fb10fcbe5fb
  Author: Mingming Liu <mingmingl at google.com>
  Date:   2024-04-10 (Wed, 10 Apr 2024)

  Changed paths:
    M clang/test/CodeGen/thinlto-distributed-cfi-devirt.ll
    M clang/test/CodeGen/thinlto-distributed-cfi.ll
    M clang/test/CodeGen/thinlto-funcattr-prop.ll
    M lld/test/ELF/lto/comdat-nodeduplicate.ll
    M llvm/include/llvm/AsmParser/LLParser.h
    M llvm/include/llvm/AsmParser/LLToken.h
    M llvm/include/llvm/IR/ModuleSummaryIndex.h
    M llvm/include/llvm/IR/ModuleSummaryIndexYAML.h
    M llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
    M llvm/lib/AsmParser/LLLexer.cpp
    M llvm/lib/AsmParser/LLParser.cpp
    M llvm/lib/Bitcode/Reader/BitcodeReader.cpp
    M llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
    M llvm/lib/IR/AsmWriter.cpp
    M llvm/lib/IR/ModuleSummaryIndex.cpp
    M llvm/test/Assembler/thinlto-memprof-summary.ll
    M llvm/test/Assembler/thinlto-multiple-summaries-for-guid.ll
    M llvm/test/Assembler/thinlto-summary-visibility.ll
    M llvm/test/Assembler/thinlto-summary.ll
    M llvm/test/Assembler/thinlto-vtable-summary.ll
    M llvm/test/Bitcode/thinlto-alias.ll
    M llvm/test/Bitcode/thinlto-func-summary-vtableref-pgo.ll
    M llvm/test/Bitcode/thinlto-function-summary-callgraph-profile-summary.ll
    M llvm/test/Bitcode/thinlto-function-summary-callgraph-relbf.ll
    M llvm/test/Bitcode/thinlto-function-summary-refgraph.ll
    M llvm/test/Bitcode/thinlto-index-disassembled-by-llvm-dis.ll
    M llvm/test/Bitcode/thinlto-type-tests.ll
    M llvm/test/Bitcode/thinlto-type-vcalls.ll
    M llvm/test/ThinLTO/X86/dot-dumper.ll
    M llvm/test/ThinLTO/X86/funcattrs-prop-maythrow.ll
    M llvm/test/ThinLTO/X86/funcimport_alwaysinline.ll
    M llvm/test/ThinLTO/X86/load-store-caching.ll
    M llvm/test/Transforms/LowerTypeTests/import-unsat.ll
    M llvm/test/Transforms/WholeProgramDevirt/Inputs/import-indir.yaml
    M llvm/test/Transforms/WholeProgramDevirt/import-indir.ll

  Log Message:
  -----------
  [ThinLTO]Record import type in GlobalValueSummary::GVFlags (#87597)

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] https://github.com/llvm/llvm-project/blob/3b337242ee165554f0017b00671381ec5b1ba855/llvm/lib/Transforms/IPO/FunctionImport.cpp#L1608-L1764
[3] https://github.com/llvm/llvm-project/blob/3b337242ee165554f0017b00671381ec5b1ba855/llvm/lib/Transforms/IPO/FunctionImport.cpp#L856
[4] https://github.com/llvm/llvm-project/blob/3b337242ee165554f0017b00671381ec5b1ba855/llvm/lib/Linker/IRMover.cpp#L605



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