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

NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310129 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/MachineBlockPlacement.cpp b/lib/CodeGen/MachineBlockPlacement.cpp
index 447ad62..374b307 100644 (file)
--- a/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/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))