[MachineLICM] A command-line option to hoist even cheap instructions
Add a command-line option to enable hoisting even cheap instructions (in
low-register-pressure situations). This is turned off by default, but has
proved useful for testing purposes.
llvm-svn: 225470
diff --git a/llvm/lib/CodeGen/MachineLICM.cpp b/llvm/lib/CodeGen/MachineLICM.cpp
index 2ab0467..cb14a5c 100644
--- a/llvm/lib/CodeGen/MachineLICM.cpp
+++ b/llvm/lib/CodeGen/MachineLICM.cpp
@@ -49,6 +49,11 @@
cl::desc("MachineLICM should avoid speculation"),
cl::init(true), cl::Hidden);
+static cl::opt<bool>
+HoistCheapInsts("hoist-cheap-insts",
+ cl::desc("MachineLICM should hoist even cheap instructions"),
+ cl::init(false), cl::Hidden);
+
STATISTIC(NumHoisted,
"Number of machine instructions hoisted out of loops");
STATISTIC(NumLowRP,
@@ -1075,7 +1080,7 @@
// Don't hoist cheap instructions if they would increase register pressure,
// even if we're under the limit.
- if (CheapInstr)
+ if (CheapInstr && !HoistCheapInsts)
return true;
for (unsigned i = BackTrace.size(); i != 0; --i) {