Add constant blinding/pooling option for X8632 code translation

src/IceOperand.cpp

 //===- subzero/src/IceOperand.cpp - High-level operand 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 Operand class and its target-independent
@@ skipping 74 matching lines @@
     if (OtherBegin < I->first) {
       Result = false;
       break;
     }
     if (OtherBegin < I->second) {
       Result = true;
       break;
     }
   }
 #if 0
-  // An equivalent but less inefficient implementation:
-  LiveRange Temp;
-  Temp.addSegment(OtherBegin, OtherBegin + 1);
-  bool Validation = overlaps(Temp);
-  assert(Result == Validation);
+                // An equivalent but less inefficient implementation:
+                LiveRange Temp;
+                Temp.addSegment(OtherBegin, OtherBegin + 1);
+                bool Validation = overlaps(Temp);
+                assert(Result == Validation);
 #endif

[JF, 2015/06/17 11:29:18]

`#if 0` and tabs are sad. Could you make this a comment, if it's useful to keep?

[qining, 2015/06/17 18:20:36]

Sorry for the unnecessary tabs. I will remove them. But I'm not so sure the
purpose of this '#if 0' here.

[Jim Stichnoth, 2015/06/19 16:51:02]

Let's keep the #if code.  This was meant to give a much clearer documentation of
the semantics, and validate that the more complex optimized implementation gives
the same result.  But it's expensive enough that I never want it on except in
emergencies.

   return Result;
 }
 
 // Returns true if the live range contains the given instruction
 // number.  This is only used for validating the live range
 // calculation.  The IsDest argument indicates whether the Variable
 // being tested is used in the Dest position (as opposed to a Src
 // position).
 bool LiveRange::containsValue(InstNumberT Value, bool IsDest) const {
   for (const RangeElementType &I : Range) {
@@ skipping 373 matching lines @@
 Ostream &operator<<(Ostream &Str, const RegWeight &W) {
   if (!ALLOW_DUMP)
     return Str;
   if (W.getWeight() == RegWeight::Inf)
     Str << "Inf";
   else
     Str << W.getWeight();
   return Str;
 }
 
+// =========== Immediate Randomization and Pooling routines ==============
+// Immediates randomization and pooling threshold, we should not
+// randomize or pool small constants e.g. 2,4 etc.
+const uint32_t X86_INT_IMMEDIATE_RANDOMIZATION_THRESHOLD = 0x1;

[qining, 2015/06/17 04:28:55]

The THRESHOLD is set to 0x1.

[JF, 2015/06/17 11:29:18]

This isn't use by other files? It's currently exported to them, and could cause
ODR (unlikely given the name). It should be static per LLVM's coding convention
(C++ usually prefers anonymous namespace, but not LLVM).

[qining, 2015/06/17 18:20:36]

Yes, you are right, I should confine this to a smaller scope. It can be either a
static constant or a local constant in the shouldBeRandomizeOrPooled() method
below.

+
+// Specialization of the template member function for ConstantInteger32
+template <>
+bool ConstantInteger32::shouldBeRandomizedOrPooled(const GlobalContext *Ctx) {
+  if (Ctx->getFlags().getRandomizeAndPoolImmediatesOption() == RPI_None)
+    return false;
+  if (getType() != IceType_i32 && getType() != IceType_i16 &&
+      getType() != IceType_i8)

[qining, 2015/06/17 04:28:55]

Consider i8, 16 constant integers.

+    return false;
+  // if(getType() != IceType_i32)  return false;
+  // The Following checks if the signed representation of Value is between
+  // -THRESHOLD/2 and +THRESHOLD/2
+  bool largerThanThreshold =
+      X86_INT_IMMEDIATE_RANDOMIZATION_THRESHOLD / 2 + Value >=
+      X86_INT_IMMEDIATE_RANDOMIZATION_THRESHOLD;
+  return largerThanThreshold;
+}
+
 } // end of namespace Ice