Clarify iOS flush-to-zero status.

src/core/SkFloatBits.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkFloatBits.h"
 #include "SkMathPriv.h"
 
@@ skipping 67 matching lines @@
         } else {
             value <<= exp;
         }
         // apply the sign after we check for overflow
         return SkApplySign(value, SkExtractSign(packed));
     } else {
         // apply the sign before we right-shift
         value = SkApplySign(value, SkExtractSign(packed));
         exp = -exp;
         if (exp > 25) {   // underflow
-#ifdef SK_DISCARD_DENORMALIZED_FOR_SPEED
+#ifdef SK_CPU_FLUSH_TO_ZERO
         // The iOS ARM processor discards small denormalized numbers to go faster.
         // The comparision below empirically causes the result to agree with the
         // tests in MathTest test_float_floor
             if (exp > 149) {
                 return 0;
             }
 #else
             exp = 25;
 #endif
         }
@@ skipping 48 matching lines @@
         } else {
             value <<= exp;
         }
         // apply the sign after we check for overflow
         return SkApplySign(value, SkExtractSign(packed));
     } else {
         // apply the sign before we right-shift
         value = SkApplySign(value, SkExtractSign(packed));
         exp = -exp;
         if (exp > 25) {   // underflow
-#ifdef SK_DISCARD_DENORMALIZED_FOR_SPEED
+#ifdef SK_CPU_FLUSH_TO_ZERO
         // The iOS ARM processor discards small denormalized numbers to go faster.
         // The comparision below empirically causes the result to agree with the
         // tests in MathTest test_float_ceil
             if (exp > 149) {
                 return 0;
             }
             return 0 < value;
 #else
             exp = 25;
 #endif
@@ skipping 28 matching lines @@
     }
 
     // now value is left-aligned to 24 bits
     SkASSERT((value >> 23) == 1);
     SkASSERT(shift >= 0 && shift <= 255);
 
     SkFloatIntUnion data;
     data.fSignBitInt = (sign << 31) | (shift << 23) | (value & ~MATISSA_MAGIC_BIG);
     return data.fFloat;
 }