BlockPlacement: add a flag to force cold block outlining w/o a profile.

NFC.

llvm-svn: 310129

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
index 447ad629885..374b3079c34 100644
--- a/llvm/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
@@ -91,6 +91,11 @@ static cl::opt<unsigned> LoopToColdBlockRatio(
              "(frequency of block) is greater than this ratio"),
     cl::init(5), cl::Hidden);
 
+static cl::opt<bool> ForceLoopColdBlock(
+    "force-loop-cold-block",
+    cl::desc("Force outlining cold blocks from loops."),
+    cl::init(false), cl::Hidden);
+
 static cl::opt<bool>
     PreciseRotationCost("precise-rotation-cost",
                         cl::desc("Model the cost of loop rotation more "
@@ -2146,7 +2151,7 @@ MachineBlockPlacement::collectLoopBlockSet(const MachineLoop &L) {
   // will be merged into the first outer loop chain for which this block is not
   // cold anymore. This needs precise profile data and we only do this when
   // profile data is available.
-  if (F->getFunction()->getEntryCount()) {
+  if (F->getFunction()->getEntryCount() || ForceLoopColdBlock) {
     BlockFrequency LoopFreq(0);
     for (auto LoopPred : L.getHeader()->predecessors())
       if (!L.contains(LoopPred))