[ThinLTO] Add an import cutoff for debugging/triaging
Summary:
Adds -import-cutoff=N which will stop importing during the thin link
after N imports. Default is -1 (no limit).
Reviewers: wmi
Subscribers: inglorion, llvm-commits
Differential Revision: https://reviews.llvm.org/D45127
llvm-svn: 328934
diff --git a/llvm/lib/Transforms/IPO/FunctionImport.cpp b/llvm/lib/Transforms/IPO/FunctionImport.cpp
index d021b4a..26d7db1 100644
--- a/llvm/lib/Transforms/IPO/FunctionImport.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionImport.cpp
@@ -71,6 +71,10 @@
"import-instr-limit", cl::init(100), cl::Hidden, cl::value_desc("N"),
cl::desc("Only import functions with less than N instructions"));
+static cl::opt<int> ImportCutoff(
+ "import-cutoff", cl::init(-1), cl::Hidden, cl::value_desc("N"),
+ cl::desc("Only import first N functions if N>=0 (default -1)"));
+
static cl::opt<float>
ImportInstrFactor("import-instr-evolution-factor", cl::init(0.7),
cl::Hidden, cl::value_desc("x"),
@@ -276,11 +280,18 @@
StringMap<FunctionImporter::ExportSetTy> *ExportLists = nullptr) {
computeImportForReferencedGlobals(Summary, DefinedGVSummaries, ImportList,
ExportLists);
+ static int ImportCount = 0;
for (auto &Edge : Summary.calls()) {
ValueInfo VI = Edge.first;
DEBUG(dbgs() << " edge -> " << VI.getGUID() << " Threshold:" << Threshold
<< "\n");
+ if (ImportCutoff >= 0 && ImportCount >= ImportCutoff) {
+ DEBUG(dbgs() << "ignored! import-cutoff value of " << ImportCutoff
+ << " reached.\n");
+ continue;
+ }
+
VI = updateValueInfoForIndirectCalls(Index, VI);
if (!VI)
continue;
@@ -343,6 +354,8 @@
// Mark this function as imported in this module, with the current Threshold
ProcessedThreshold = AdjThreshold;
+ ImportCount++;
+
// Make exports in the source module.
if (ExportLists) {
auto &ExportList = (*ExportLists)[ExportModulePath];
diff --git a/llvm/test/Transforms/FunctionImport/Inputs/funcimport_cutoff.ll b/llvm/test/Transforms/FunctionImport/Inputs/funcimport_cutoff.ll
new file mode 100644
index 0000000..4283215
--- /dev/null
+++ b/llvm/test/Transforms/FunctionImport/Inputs/funcimport_cutoff.ll
@@ -0,0 +1,9 @@
+define void @foo() {
+entry:
+ ret void
+}
+
+define void @bar() {
+entry:
+ ret void
+}
diff --git a/llvm/test/Transforms/FunctionImport/funcimport_cutoff.ll b/llvm/test/Transforms/FunctionImport/funcimport_cutoff.ll
new file mode 100644
index 0000000..dac4bd1
--- /dev/null
+++ b/llvm/test/Transforms/FunctionImport/funcimport_cutoff.ll
@@ -0,0 +1,49 @@
+; Test to ensure that thin linking with -import-cutoff stops importing when
+; expected.
+
+; "-stats" and "-debug-only" require +Asserts.
+; REQUIRES: asserts
+
+; RUN: opt -module-summary %s -o %t.bc
+; RUN: opt -module-summary %p/Inputs/funcimport_cutoff.ll -o %t2.bc
+; RUN: llvm-lto -thinlto -o %t3 %t.bc %t2.bc
+
+; First do with default options, which should import both foo and bar
+; RUN: opt -function-import -stats -print-imports -summary-file %t3.thinlto.bc %t.bc -S 2>&1 | FileCheck %s --check-prefix=IMPORT
+
+; Next try to restrict to 1 import. This should import just foo.
+; RUN: opt -import-cutoff=1 -function-import -stats -print-imports -summary-file %t3.thinlto.bc %t.bc -S 2>&1 | FileCheck %s --check-prefix=IMPORT1
+
+; Next try to restrict to 0 imports. This should not import.
+; RUN: opt -import-cutoff=0 -function-import -stats -print-imports -summary-file %t3.thinlto.bc %t.bc -S 2>&1 | FileCheck %s --check-prefix=NOIMPORT
+
+define i32 @main() {
+entry:
+ call void @foo()
+ call void @bar()
+ ret i32 0
+}
+
+declare void @foo()
+declare void @bar()
+
+; Check -print-imports output
+; IMPORT: Import foo
+; IMPORT: Import bar
+; IMPORT1: Import foo
+; IMPORT1-NOT: Import bar
+; NOIMPORT-NOT: Import foo
+; NOIMPORT-NOT: Import bar
+
+; Check -S output
+; IMPORT-DAG: define available_externally void @foo()
+; IMPORT-DAG: define available_externally void @bar()
+; NOIMPORT-DAG: declare void @foo()
+; NOIMPORT-DAG: declare void @bar()
+; IMPORT1-DAG: define available_externally void @foo()
+; IMPORT1-DAG: declare void @bar()
+
+; Check -stats output
+; IMPORT: 2 function-import - Number of functions imported
+; IMPORT1: 1 function-import - Number of functions imported
+; NOIMPORT-NOT: function-import - Number of functions imported