[thinlto] Add cold-callsite import heuristic
Summary:
Not tunned up heuristic, but with this small heuristic there is about
+0.10% improvement on SPEC 2006
Reviewers: tejohnson, mehdi_amini, eraman
Subscribers: mehdi_amini, llvm-commits
Differential Revision: https://reviews.llvm.org/D24940
llvm-svn: 282733
diff --git a/llvm/lib/Transforms/IPO/FunctionImport.cpp b/llvm/lib/Transforms/IPO/FunctionImport.cpp
index 6c43b78..58877b1 100644
--- a/llvm/lib/Transforms/IPO/FunctionImport.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionImport.cpp
@@ -48,10 +48,15 @@
cl::desc("As we import functions, multiply the "
"`import-instr-limit` threshold by this factor "
"before processing newly imported functions"));
+
static cl::opt<float> ImportHotMultiplier(
"import-hot-multiplier", cl::init(3.0), cl::Hidden, cl::value_desc("x"),
- cl::ZeroOrMore, cl::desc("Multiply the `import-instr-limit` threshold for "
- "hot callsites"));
+ cl::desc("Multiply the `import-instr-limit` threshold for hot callsites"));
+
+// FIXME: This multiplier was not really tuned up.
+static cl::opt<float> ImportColdMultiplier(
+ "import-cold-multiplier", cl::init(0), cl::Hidden, cl::value_desc("N"),
+ cl::desc("Multiply the `import-instr-limit` threshold for cold callsites"));
static cl::opt<bool> PrintImports("print-imports", cl::init(false), cl::Hidden,
cl::desc("Print imported functions"));
@@ -285,11 +290,16 @@
continue;
}
- // FIXME: Also lower the threshold for cold callsites.
+ auto GetBonusMultiplier = [](CalleeInfo::HotnessType Hotness) -> float {
+ if (Hotness == CalleeInfo::HotnessType::Hot)
+ return ImportHotMultiplier;
+ if (Hotness == CalleeInfo::HotnessType::Cold)
+ return ImportColdMultiplier;
+ return 1.0;
+ };
+
const auto NewThreshold =
- Edge.second.Hotness == CalleeInfo::HotnessType::Hot
- ? Threshold * ImportHotMultiplier
- : Threshold;
+ Threshold * GetBonusMultiplier(Edge.second.Hotness);
auto *CalleeSummary = selectCallee(GUID, NewThreshold, Index);
if (!CalleeSummary) {
DEBUG(dbgs() << "ignored! No qualifying callee with summary found.\n");