Saturated arithmetic changed to use templates to fix build-issues

Source/wtf/asm/SaturatedArithmeticARM.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SaturatedArithmeticARM_h
 #define SaturatedArithmeticARM_h
 
 #include "wtf/CPU.h"
 #include <limits>
 #include <stdint.h>
@@ skipping 15 matching lines @@
     int32_t result;
 
     asm("qsub %[output],%[first],%[second]"
         :   [output] "=r"  (result)
         :   [first]  "r"   (a),
             [second] "r"   (b));
 
     return result;
 }
 
-inline int getMaxSaturatedSetResultForTesting(int FractionalShift)
+inline int getMaxSaturatedSetResultForTesting(int fractionalShift)
 {
     // For ARM Asm version the set function maxes out to the biggest
     // possible integer part with the fractional part zero'd out.
     // e.g. 0x7fffffc0.
-    return std::numeric_limits<int>::max() & ~((1 << FractionalShift)-1);
+    return std::numeric_limits<int>::max() & ~((1 << fractionalShift)-1);
 }
 
-inline int getMinSaturatedSetResultForTesting(int FractionalShift)
+inline int getMinSaturatedSetResultForTesting(int fractionalShift)
 {
     return std::numeric_limits<int>::min();
 }
 
-ALWAYS_INLINE int saturatedSet(int value, int FractionalShift)
+template<size_t saturate, size_t fractionalShift>
+ALWAYS_INLINE int saturatedSetSigned(int value)
 {
-    // Figure out how many bits are left for storing the integer part of
-    // the fixed point number, and saturate our input to that
-    const int saturate = 32 - FractionalShift;
-
     int result;
-
-    // The following ARM code will Saturate the passed value to the number of
-    // bits used for the whole part of the fixed point representation, then
-    // shift it up into place. This will result in the low <FractionShift> bits
-    // all being 0's. When the value saturates this gives a different result
-    // to from the C++ case; in the C++ code a saturated value has all the low
-    // bits set to 1 (for a +ve number at least). This cannot be done rapidly
-    // in ARM ... we live with the difference, for the sake of speed.
-
+    // To allow all compilers to correctly build this asm we need to use
+    // template specialization to ensure that the "n" parameters are
+    // compile-time constant values.
     asm("ssat %[output],%[saturate],%[value]\n\t"
         "lsl  %[output],%[shift]"
         :   [output]    "=r"  (result)
         :   [value]     "r"   (value),
             [saturate]  "n"   (saturate),
-            [shift]     "n"   (FractionalShift));
+            [shift]     "n"   (fractionalShift));
 
     return result;
 }
 
-
-ALWAYS_INLINE int saturatedSet(unsigned value, int FractionalShift)
+template<size_t saturate, size_t fractionalShift>
+ALWAYS_INLINE int saturatedSetUnsigned(unsigned value)
 {
-    // Here we are being passed an unsigned value to saturate,
-    // even though the result is returned as a signed integer. The ARM
-    // instruction for unsigned saturation therefore needs to be given one
-    // less bit (i.e. the sign bit) for the saturation to work correctly; hence
-    // the '31' below.
-    const int saturate = 31 - FractionalShift;
-
-    // The following ARM code will Saturate the passed value to the number of
-    // bits used for the whole part of the fixed point representation, then
-    // shift it up into place. This will result in the low <FractionShift> bits
-    // all being 0's. When the value saturates this gives a different result
-    // to from the C++ case; in the C++ code a saturated value has all the low
-    // bits set to 1. This cannot be done rapidly in ARM, so we live with the
-    // difference, for the sake of speed.
-
     int result;
-
+    // To allow all compilers to correctly build this asm we need to use
+    // template specialization to ensure that the "n" parameters are
+    // compile-time constant values.
     asm("usat %[output],%[saturate],%[value]\n\t"
         "lsl  %[output],%[shift]"
         :   [output]    "=r"  (result)
         :   [value]     "r"   (value),
             [saturate]  "n"   (saturate),
-            [shift]     "n"   (FractionalShift));
+            [shift]     "n"   (fractionalShift));
 
     return result;
 }
 
 #endif // SaturatedArithmeticARM_h