From dda73336ad22bd0b5ecda17040c50fb10fcbe5fb Mon Sep 17 00:00:00 2001 From: Mingming Liu Date: Wed, 10 Apr 2024 19:46:01 -0700 Subject: [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 ``. 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 --- llvm/lib/IR/AsmWriter.cpp | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'llvm/lib/IR/AsmWriter.cpp') diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp index b778a14..609de92 100644 --- a/llvm/lib/IR/AsmWriter.cpp +++ b/llvm/lib/IR/AsmWriter.cpp @@ -3306,6 +3306,16 @@ static const char *getVisibilityName(GlobalValue::VisibilityTypes Vis) { llvm_unreachable("invalid visibility"); } +static const char *getImportTypeName(GlobalValueSummary::ImportKind IK) { + switch (IK) { + case GlobalValueSummary::Definition: + return "definition"; + case GlobalValueSummary::Declaration: + return "declaration"; + } + assert(false && "invalid import kind"); +} + void AssemblyWriter::printFunctionSummary(const FunctionSummary *FS) { Out << ", insts: " << FS->instCount(); if (FS->fflags().anyFlagSet()) @@ -3545,6 +3555,8 @@ void AssemblyWriter::printSummary(const GlobalValueSummary &Summary) { Out << ", live: " << GVFlags.Live; Out << ", dsoLocal: " << GVFlags.DSOLocal; Out << ", canAutoHide: " << GVFlags.CanAutoHide; + Out << ", importType: " + << getImportTypeName(GlobalValueSummary::ImportKind(GVFlags.ImportType)); Out << ")"; if (Summary.getSummaryKind() == GlobalValueSummary::AliasKind) -- cgit v1.1