Simplify floating-point comparisons with NaN in Optimizing.

This change was suggested by Ian.

Also, simplify some art::HFloatConstant and
art::HDoubleConstant methods.

Change-Id: I7908df23581a7f61c8ec79c290fe5f70798ac3be

1 files changed, 21 insertions, 0 deletions

diff --git a/compiler/optimizing/constant_folding.cc b/compiler/optimizing/constant_folding.cc
index b7a92b5ae5..5a1d9b488f 100644
--- a/compiler/optimizing/constant_folding.cc
+++ b/compiler/optimizing/constant_folding.cc
@@ -28,6 +28,7 @@ class InstructionWithAbsorbingInputSimplifier : public HGraphVisitor {
   void VisitShift(HBinaryOperation* shift);
 
   void VisitAnd(HAnd* instruction) OVERRIDE;
+  void VisitCompare(HCompare* instruction) OVERRIDE;
   void VisitMul(HMul* instruction) OVERRIDE;
   void VisitOr(HOr* instruction) OVERRIDE;
   void VisitRem(HRem* instruction) OVERRIDE;
@@ -108,6 +109,26 @@ void InstructionWithAbsorbingInputSimplifier::VisitAnd(HAnd* instruction) {
   }
 }
 
+void InstructionWithAbsorbingInputSimplifier::VisitCompare(HCompare* instruction) {
+  HConstant* input_cst = instruction->GetConstantRight();
+  if (input_cst != nullptr) {
+    HInstruction* input_value = instruction->GetLeastConstantLeft();
+    if (Primitive::IsFloatingPointType(input_value->GetType()) &&
+        ((input_cst->IsFloatConstant() && input_cst->AsFloatConstant()->IsNaN()) ||
+         (input_cst->IsDoubleConstant() && input_cst->AsDoubleConstant()->IsNaN()))) {
+      // Replace code looking like
+      //    CMP{G,L} dst, src, NaN
+      // with
+      //    CONSTANT +1 (gt bias)
+      // or
+      //    CONSTANT -1 (lt bias)
+      instruction->ReplaceWith(GetGraph()->GetConstant(Primitive::kPrimInt,
+                                                       (instruction->IsGtBias() ? 1 : -1)));
+      instruction->GetBlock()->RemoveInstruction(instruction);
+    }
+  }
+}
+
 void InstructionWithAbsorbingInputSimplifier::VisitMul(HMul* instruction) {
   HConstant* input_cst = instruction->GetConstantRight();
   Primitive::Type type = instruction->GetType();