Revert "[optimizing] Replace FP divide by power of 2"

Fails compiling docs.

This reverts commit b0bd8915cb257cdaf46ba663c450a6543bca75af.

Change-Id: I47d32525c83a73118e2163eb58c68bbb7a28bb38

4 files changed, 8 insertions, 137 deletions

diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index 0013b72c43..b8ae1f6369 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -39,7 +39,6 @@ class InstructionSimplifierVisitor : public HGraphVisitor {
   }
 
   bool TryMoveNegOnInputsAfterBinop(HBinaryOperation* binop);
-  bool IsExactFPPowerOfTwo(HConstant* constant);
   void VisitShift(HBinaryOperation* shift);
 
   void VisitSuspendCheck(HSuspendCheck* check) OVERRIDE;
@@ -381,72 +380,6 @@ void InstructionSimplifierVisitor::VisitDiv(HDiv* instruction) {
         instruction, (new (GetGraph()->GetArena()) HNeg(type, input_other)));
     RecordSimplification();
   }
-
-  // FP Handle division by powers of 2.
-  if ((input_cst != nullptr) && Primitive::IsFloatingPointType(type) &&
-        IsExactFPPowerOfTwo(input_cst)) {
-    // We can replace this by a multiplication by the reciprocal.
-    // We know that since the value is an exact power of 2, there is no precision lost.
-    HConstant *recip;
-    if (type == Primitive::Primitive::kPrimDouble) {
-      double recip_value = 1.0 / input_cst->AsDoubleConstant()->GetValue();
-      recip = GetGraph()->GetDoubleConstant(recip_value);
-    } else {
-      DCHECK_EQ(type, Primitive::kPrimFloat);
-      float recip_value = 1.0f / input_cst->AsFloatConstant()->GetValue();
-      recip = GetGraph()->GetFloatConstant(recip_value);
-    }
-    instruction->GetBlock()->ReplaceAndRemoveInstructionWith(
-        instruction, (new (GetGraph()->GetArena()) HMul(type, input_other, recip)));
-    RecordSimplification();
-  }
-}
-
-
-bool InstructionSimplifierVisitor::IsExactFPPowerOfTwo(HConstant* constant) {
-  if (constant->IsDoubleConstant()) {
-    // We will examine the value as an unsigned value.
-    uint64_t value = bit_cast<uint64_t, double>(constant->AsDoubleConstant()->GetValue());
-
-    // Make sure the double constant is power of 2.0, so that we can have the
-    // exact result after converting value to 1.0/value.
-    // The uint64_t value is 0 from bit 51 to bit 0.
-    if ((value & INT64_C(0x000FFFFFFFFFFFFF)) != 0) {
-      return false;
-    }
-
-    // For the double constant, we support the range 2.0^-1022 to 2.0^1022
-    // or -(2.0^-1022) to -(2.0^1022)
-    // The uint64_t value is from 0x0010000000000000 to 0x7FD0000000000000 or
-    // from 0x8010000000000000 to 0xFFD0000000000000.
-    if ((value < INT64_C(0x0010000000000000) || value > INT64_C(0x7FD0000000000000)) &&
-        (value < INT64_C(0x8010000000000000) || value > INT64_C(0xFFD0000000000000))) {
-      return false;
-    }
-  } else {
-    DCHECK(constant->IsFloatConstant());
-    // We will examine the value as an unsigned value.
-    uint32_t value = bit_cast<uint32_t, float>(constant->AsFloatConstant()->GetValue());
-
-    // Make sure the float constant is power of 2.0, so that we can have the
-    // exact result after converting value to 1.0/value.
-    // The uint32_t value is 0 from bit 22 to bit 0.
-    if ((value & 0x007FFFFF) != 0) {
-      return false;
-    }
-
-    // For the float constant, we support the range 2.0^-126 to 2.0^126
-    // or -(2.0^-126) to -(2.0^126)
-    // The uint32_t value is from 0x00800000 to 0x7E800000 or
-    // from 0x80800000 to 0xFE800000.
-    if ((value < 0x00800000 || value > 0x7E800000) &&
-        (value < 0x80800000 || value > 0xFE800000)) {
-      return false;
-    }
-  }
-
-  // This is a proper FP power of two.
-  return true;
 }
 
 void InstructionSimplifierVisitor::VisitMul(HMul* instruction) {
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index 6020196493..5fca4fab22 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -343,18 +343,6 @@ HConstant* HGraph::GetConstant(Primitive::Type type, int64_t value) {
   }
 }
 
-HFloatConstant* HGraph::GetFloatConstant(float value) {
-  HFloatConstant *constant = new (arena_) HFloatConstant(value);
-  InsertConstant(constant);
-  return constant;
-}
-
-HDoubleConstant* HGraph::GetDoubleConstant(double value) {
-  HDoubleConstant *constant = new (arena_) HDoubleConstant(value);
-  InsertConstant(constant);
-  return constant;
-}
-
 void HLoopInformation::Add(HBasicBlock* block) {
   blocks_.SetBit(block->GetBlockId());
 }
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 3e922a0065..d9d15c4b18 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -234,7 +234,7 @@ class HGraph : public ArenaObject<kArenaAllocMisc> {
 
   // Returns a constant of the given type and value. If it does not exist
   // already, it is created and inserted into the graph. Only integral types
-  // are currently cached.
+  // are currently supported.
   HConstant* GetConstant(Primitive::Type type, int64_t value);
   HNullConstant* GetNullConstant();
   HIntConstant* GetIntConstant(int32_t value) {
@@ -243,8 +243,6 @@ class HGraph : public ArenaObject<kArenaAllocMisc> {
   HLongConstant* GetLongConstant(int64_t value) {
     return CreateConstant(value, &cached_long_constants_);
   }
-  HFloatConstant* GetFloatConstant(float value);
-  HDoubleConstant* GetDoubleConstant(double value);
 
  private:
   HBasicBlock* FindCommonDominator(HBasicBlock* first, HBasicBlock* second) const;
@@ -2022,9 +2020,10 @@ class HFloatConstant : public HConstant {
 
   const float value_;
 
-  // Only the SsaBuilder and HGraph can create floating-point constants.
+  // Only the SsaBuilder can currently create floating-point constants. If we
+  // ever need to create them later in the pipeline, we will have to handle them
+  // the same way as integral constants.
   friend class SsaBuilder;
-  friend class HGraph;
   DISALLOW_COPY_AND_ASSIGN(HFloatConstant);
 };
 
@@ -2058,9 +2057,10 @@ class HDoubleConstant : public HConstant {
 
   const double value_;
 
-  // Only the SsaBuilder and HGraph can create floating-point constants.
+  // Only the SsaBuilder can currently create floating-point constants. If we
+  // ever need to create them later in the pipeline, we will have to handle them
+  // the same way as integral constants.
   friend class SsaBuilder;
-  friend class HGraph;
   DISALLOW_COPY_AND_ASSIGN(HDoubleConstant);
 };
 
diff --git a/test/458-checker-instruction-simplification/src/Main.java b/test/458-checker-instruction-simplification/src/Main.java
index f26e0b1a8a..65be6cb4c4 100644
--- a/test/458-checker-instruction-simplification/src/Main.java
+++ b/test/458-checker-instruction-simplification/src/Main.java
@@ -34,18 +34,6 @@ public class Main {
     }
   }
 
-  public static void assertFloatEquals(float expected, float result) {
-    if (expected != result) {
-      throw new Error("Expected: " + expected + ", found: " + result);
-    }
-  }
-
-  public static void assertDoubleEquals(double expected, double result) {
-    if (expected != result) {
-      throw new Error("Expected: " + expected + ", found: " + result);
-    }
-  }
-
   /**
    * Tiny programs exercising optimizations of arithmetic identities.
    */
@@ -919,43 +907,6 @@ public class Main {
     return !(!arg);
   }
 
-  // CHECK-START: float Main.Div2(float) instruction_simplifier (before)
-  // CHECK-DAG:     [[Arg:f\d+]]      ParameterValue
-  // CHECK-DAG:     [[Const2:f\d+]]   FloatConstant 2
-  // CHECK-DAG:     [[Div:f\d+]]      Div [ [[Arg]] [[Const2]] ]
-  // CHECK-DAG:                       Return [ [[Div]] ]
-
-  // CHECK-START: float Main.Div2(float) instruction_simplifier (after)
-  // CHECK-DAG:     [[Arg:f\d+]]      ParameterValue
-  // CHECK-DAG:     [[ConstP5:f\d+]]  FloatConstant 0.5
-  // CHECK-DAG:     [[Mul:f\d+]]      Mul [ [[Arg]] [[ConstP5]] ]
-  // CHECK-DAG:                       Return [ [[Mul]] ]
-
-  // CHECK-START: float Main.Div2(float) instruction_simplifier (after)
-  // CHECK-NOT:                       Div
-
-  public static float Div2(float arg) {
-    return arg / 2.0f;
-  }
-
-  // CHECK-START: double Main.Div2(double) instruction_simplifier (before)
-  // CHECK-DAG:     [[Arg:d\d+]]      ParameterValue
-  // CHECK-DAG:     [[Const2:d\d+]]   DoubleConstant 2
-  // CHECK-DAG:     [[Div:d\d+]]      Div [ [[Arg]] [[Const2]] ]
-  // CHECK-DAG:                       Return [ [[Div]] ]
-
-  // CHECK-START: double Main.Div2(double) instruction_simplifier (after)
-  // CHECK-DAG:     [[Arg:d\d+]]      ParameterValue
-  // CHECK-DAG:     [[ConstP5:d\d+]]  DoubleConstant 0.5
-  // CHECK-DAG:     [[Mul:d\d+]]      Mul [ [[Arg]] [[ConstP5]] ]
-  // CHECK-DAG:                       Return [ [[Mul]] ]
-
-  // CHECK-START: double Main.Div2(double) instruction_simplifier (after)
-  // CHECK-NOT:                       Div
-  public static double Div2(double arg) {
-    return arg / 2.0;
-  }
-
   public static void main(String[] args) {
     int arg = 123456;
 
@@ -990,6 +941,7 @@ public class Main {
     assertIntEquals(SubNeg1(arg, arg + 1), -(arg + arg + 1));
     assertIntEquals(SubNeg2(arg, arg + 1), -(arg + arg + 1));
     assertLongEquals(SubNeg3(arg, arg + 1), -(2 * arg + 1));
+
     assertIntEquals(EqualTrueRhs(true), 5);
     assertIntEquals(EqualTrueLhs(true), 5);
     assertIntEquals(EqualFalseRhs(true), 3);
@@ -1000,7 +952,5 @@ public class Main {
     assertIntEquals(NotEqualFalseLhs(true), 5);
     assertBooleanEquals(NotNotBool(true), true);
     assertBooleanEquals(NotNotBool(false), false);
-    assertFloatEquals(Div2(100.0f), 50.0f);
-    assertDoubleEquals(Div2(150.0), 75.0);
   }
 }