Subzero: Randomly insert nops.

src/IceTargetLowering.cpp

 //===- subzero/src/IceTargetLowering.cpp - Basic lowering implementation --===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the skeleton of the TargetLowering class,
 // specifically invoking the appropriate lowering method for a given
 // instruction kind and driving global register allocation.  It also
 // implements the non-deleted instruction iteration in
 // LoweringContext.
 //
 //===----------------------------------------------------------------------===//
 
 #include "IceCfg.h" // setError()
 #include "IceCfgNode.h"
 #include "IceOperand.h"
 #include "IceRegAlloc.h"
 #include "IceTargetLowering.h"
 #include "IceTargetLoweringX8632.h"
 
+#include "llvm/Support/CommandLine.h"
+
 namespace Ice {
 
+namespace {
+
+namespace cl = llvm::cl;
+cl::opt<bool> DoNopInsertion("nop-insertion", cl::desc("Randomly insert NOPs"),
+                             cl::init(false));
+
+cl::opt<int> MaxNopsPerInstruction(
+    "max-nops-per-instruction",
+    cl::desc("Max number of nops to insert per instruction"), cl::init(1));
+
+cl::opt<int> NopProbabilityAsPercentage(
+    "nop-insertion-percentage",
+    cl::desc("Nop insertion probability as percentage"), cl::init(10));
+} // end of anonymous namespace
+
 void LoweringContext::init(CfgNode *N) {
   Node = N;
   Begin = getNode()->getInsts().begin();
   Cur = Begin;
   End = getNode()->getInsts().end();
   skipDeleted(Cur);
   Next = Cur;
   advanceForward(Next);
 }
 
@@ skipping 46 matching lines @@
 
 void TargetLowering::doAddressOpt() {
   if (llvm::isa<InstLoad>(*Context.getCur()))
     doAddressOptLoad();
   else if (llvm::isa<InstStore>(*Context.getCur()))
     doAddressOptStore();
   Context.advanceCur();
   Context.advanceNext();
 }
 
+bool TargetLowering::shouldDoNopInsertion() const { return DoNopInsertion; }
+
+void TargetLowering::doNopInsertion() {
+  Inst *I = *Context.getCur();
+  bool ShouldSkip = llvm::isa<InstFakeUse>(I) || llvm::isa<InstFakeDef>(I) ||
+                    llvm::isa<InstFakeKill>(I) || I->isRedundantAssign() ||
+                    I->isDeleted();
+  if (!ShouldSkip) {
+    for (int I = 0; I < MaxNopsPerInstruction; ++I) {
+      randomlyInsertNop(NopProbabilityAsPercentage / 100.0);
+    }
+  }
+}
+
 // 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
 // target instructions at the Cur.Next insertion point, and should not
 // delete the Context.Cur instruction or advance Context.Cur.
 //
 // The lowering method may look ahead in the instruction stream as
 // desired, and lower additional instructions in conjunction with the
 // current one, for example fusing a compare and branch.  If it does,
 // it should advance Context.Cur to point to the next non-deleted
@@ skipping 105 matching lines @@
   if (Target == Target_ARM64)
     return IceTargetGlobalInitARM64::create(Ctx);
 #endif
   llvm_unreachable("Unsupported target");
   return NULL;
 }
 
 TargetGlobalInitLowering::~TargetGlobalInitLowering() {}
 
 } // end of namespace Ice