commit c3302746b21dcb4469efef8d484adba47c9d87e9
author Matt Wala <wala@chromium.org> Fri Aug 15 16:21:56 2014 -0700
committer Matt Wala <wala@chromium.org> Fri Aug 15 16:21:56 2014 -0700
tree 5746d018deb6c088b6d19d787c3c86ab4c6bc118
parent 9dbe38e31e72aec9869effaa325b2bab23eb8816

Subzero: Randomly insert nops.

Adds command line options -nop-insertion, -nop-insertion-probability=X, and -max-nops-per-instruction=X.

BUG=none
R=jvoung@chromium.org, stichnot@chromium.org

Review URL: https://codereview.chromium.org/463563006

src/IceTargetLoweringX8632.cpp

diff --git a/src/IceTargetLoweringX8632.cpp b/src/IceTargetLoweringX8632.cpp
index 35792aa..d36ad16 100644
--- a/src/IceTargetLoweringX8632.cpp
+++ b/src/IceTargetLoweringX8632.cpp
@@ -134,6 +134,8 @@
 const uint32_t X86_LOG2_OF_MIN_STACK_SLOT_SIZE = 2;
 // The base 2 logarithm of the width in bytes of the largest stack slot
 const uint32_t X86_LOG2_OF_MAX_STACK_SLOT_SIZE = 4;
+// The number of different NOP instructions
+const uint32_t X86_NUM_NOP_VARIANTS = 5;
 
 // Value and Alignment are in bytes.  Return Value adjusted to the next
 // highest multiple of Alignment.
@@ -391,6 +393,11 @@
     return;
   T_genFrame.printElapsedUs(Context, "genFrame()");
   Func->dump("After stack frame mapping");
+
+  // Nop insertion
+  if (shouldDoNopInsertion()) {
+    Func->doNopInsertion();
+  }
 }
 
 void TargetX8632::translateOm1() {
@@ -429,6 +436,11 @@
     return;
   T_genFrame.printElapsedUs(Context, "genFrame()");
   Func->dump("After stack frame mapping");
+
+  // Nop insertion
+  if (shouldDoNopInsertion()) {
+    Func->doNopInsertion();
+  }
 }
 
 IceString TargetX8632::RegNames[] = {
@@ -3670,6 +3682,13 @@
   }
 }
 
+void TargetX8632::randomlyInsertNop(float Probability) {
+  RandomNumberGeneratorWrapper RNG(Ctx->getRNG());
+  if (RNG.getTrueWithProbability(Probability)) {
+    _nop(RNG.next(X86_NUM_NOP_VARIANTS));
+  }
+}
+
 void TargetX8632::lowerPhi(const InstPhi * /*Inst*/) {
   Func->setError("Phi found in regular instruction list");
 }