Subzero: Randomly insert nops.

src/IceTargetLowering.cpp

Index: src/IceTargetLowering.cpp
diff --git a/src/IceTargetLowering.cpp b/src/IceTargetLowering.cpp
index 0034de5f7ca3e2340eb15e52f23530dfafc8ca56..5874e79bceb7c4407c3eeff421c04de0ac5c0e6c 100644
--- a/src/IceTargetLowering.cpp
+++ b/src/IceTargetLowering.cpp
@@ -22,8 +22,20 @@
 #include "IceTargetLowering.h"
 #include "IceTargetLoweringX8632.h"
 
+#include "llvm/Support/CommandLine.h"
+
 namespace Ice {
 
+namespace {
+namespace cl = llvm::cl;
+cl::opt<bool> DoNopInsertion("insert-nops", cl::desc("Randomly insert NOPs"),
+                             cl::init(false));
+cl::opt<int> NopProbability("nop-probability",
+                            cl::desc("Nop insertion probability"),

[jvoung (off chromium), 2014/08/14 15:17:17]

A default of "10" should be a strong hint at the units, but it would be good to
be explicit about the units -- (percentage vs 0.0 to 1.0 fraction).

[wala, 2014/08/14 23:29:50]

Done.

+                            cl::init(10));
+} // end anonymous namespace

[Jim Stichnoth, 2014/08/14 01:20:10]

end of anonymous namespace

[wala, 2014/08/14 23:29:50]

Done.

+
+
 void LoweringContext::init(CfgNode *N) {
   Node = N;
   Begin = getNode()->getInsts().begin();
@@ -90,6 +102,16 @@ void TargetLowering::doAddressOpt() {
   Context.advanceNext();
 }
 
+bool TargetLowering::shouldDoNopInsertion() const {
+  return DoNopInsertion;
+}
+
+void TargetLowering::doNopInsertion() {
+  randomlyInsertNop(NopProbability / 100.0);
+  Context.advanceCur();
+  Context.advanceNext();
+}
+
 // Lowers a single instruction according to the information in
 // Context, by checking the Context.Cur instruction kind and calling
 // the appropriate lowering method.  The lowering method should insert