ARM: Tweak ECMAToInt32VFP to address regression on Nexus 4

src/arm/macro-assembler-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2513 matching lines @@
                                     Register input_low) {
   CpuFeatureScope scope(this, VFP2);
   ASSERT(!input_high.is(result));
   ASSERT(!input_low.is(result));
   ASSERT(!input_low.is(input_high));
   ASSERT(!scratch.is(result) &&
          !scratch.is(input_high) &&
          !scratch.is(input_low));
   ASSERT(!double_input.is(double_scratch));
 
-  Label overflow, out_of_range, negate, done;
+  Label out_of_range, negate, done;
+
+  vcvt_s32_f64(double_scratch.low(), double_input);
+  vmov(result, double_scratch.low());
+
+  // If result is not saturated (0x7fffffff or 0x80000000), we are done.
+  sub(scratch, result, Operand(1));
+  cmp(scratch, Operand(0x7ffffffe));
+  b(lt, &done);
 
   vmov(input_low, input_high, double_input);
   Ubfx(scratch, input_high,
        HeapNumber::kExponentShift, HeapNumber::kExponentBits);
   // Load scratch with exponent - 1. This is faster than loading
   // with exponent because Bias + 1 = 1024 which is an *ARM* immediate value.
   sub(scratch, scratch, Operand(HeapNumber::kExponentBias + 1));
-  // Compare exponent with 31 (compare exponent - 1 with 30).
-  cmp(scratch, Operand(30));
-  b(ge, &overflow);
-  // Exponent is less than 31 so vcvt will never saturate.
-  // So, just return the result.
-  vcvt_s32_f64(double_scratch.low(), double_input);
-  vmov(result, double_scratch.low());
-  b(&done);
-
-  bind(&overflow);
   // If exponent is greater than or equal to 84, the 32 less significant
   // bits are 0s (2^84 = 1, 52 significant bits, 32 uncoded bits),
   // the result is 0.
-  // This test also catch Nan and infinities which also return 0.
   // Compare exponent with 84 (compare exponent - 1 with 83).
   cmp(scratch, Operand(83));
   b(ge, &out_of_range);
 
   // If we reach this code, 31 <= exponent <= 83.
   // So, we don't have to handle cases where 0 <= exponent <= 20 for
   // which we would need to shift right the high part of the mantissa.
   ECMAToInt32Tail(result, scratch, input_high, input_low,
                   &out_of_range, &negate, &done);
 }
@@ skipping 1385 matching lines @@
 void CodePatcher::EmitCondition(Condition cond) {
   Instr instr = Assembler::instr_at(masm_.pc_);
   instr = (instr & ~kCondMask) | cond;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM