Runtime flag to control branch funnel threshold

Reviewers: pcc

Subscribers: hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D45193

llvm-svn: 329459

1 files changed, 6 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
index a3aa7c42608..2c08cd82a5b 100644
--- a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
+++ b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
@@ -111,6 +111,11 @@ static cl::opt<std::string> ClWriteSummary(
     cl::desc("Write summary to given YAML file after running pass"),
     cl::Hidden);
 
+static cl::opt<int> ClThreshold("wholeprogramdevirt-branch-funnel-threshold",
+                                cl::Hidden, cl::init(10), cl::ZeroOrMore,
+                                cl::desc("Maximum number of call targets per "
+                                         "call site to enable branch funnels"));
+
 // Find the minimum offset that we may store a value of size Size bits at. If
 // IsAfter is set, look for an offset before the object, otherwise look for an
 // offset after the object.
@@ -820,8 +825,7 @@ void DevirtModule::tryICallBranchFunnel(
   if (T.getArch() != Triple::x86_64)
     return;
 
-  const unsigned kBranchFunnelThreshold = 10;
-  if (TargetsForSlot.size() > kBranchFunnelThreshold)
+  if (TargetsForSlot.size() > ClThreshold)
     return;
 
   bool HasNonDevirt = !SlotInfo.CSInfo.AllCallSitesDevirted;