S390: Implemented ALCR in S390 simulator.

src/s390/simulator-s390.h

Index: src/s390/simulator-s390.h
diff --git a/src/s390/simulator-s390.h b/src/s390/simulator-s390.h
index 8fee5145e66cbacc61ee49693d874646891c6b38..aaab896a0c6cbc714bb42d8322bb6d0730c29819 100644
--- a/src/s390/simulator-s390.h
+++ b/src/s390/simulator-s390.h
@@ -309,6 +309,7 @@ class Simulator {
   bool DecodeTwoByte(Instruction* instr);
   bool DecodeFourByte(Instruction* instr);
   bool DecodeFourByteArithmetic(Instruction* instr);
+  bool DecodeFourByteArithmetic64Bit(Instruction* instr);
   bool DecodeFourByteFloatingPoint(Instruction* instr);
   void DecodeFourByteFloatingPointIntConversion(Instruction* instr);
   void DecodeFourByteFloatingPointRound(Instruction* instr);
@@ -395,6 +396,27 @@ class Simulator {
     if (condition_reg_ == 0) condition_reg_ = unordered;
   }
 
+  // Used by arithmetic operations that use carry.
+  template <typename T>

[JoranSiu, 2016/03/31 13:27:57]

Not sure if this needs to be a template function, given that result is only
being compared to zero.

[bcleung, 2016/03/31 19:12:39]

This function will be used with unsigned int inputs of multiple types (e.g.
uint32 and uint64), therefore it is necessary to make it a template function.

+  void SetS390ConditionCodeCarry(T result, bool overflow) {
+    condition_reg_ = 0;
+    bool zero_result = (result == static_cast<T>(0));
+    if (zero_result && !overflow) {
+      condition_reg_ |= 8;
+    } else if (!zero_result && !overflow) {
+      condition_reg_ |= 4;
+    } else if (zero_result && overflow) {
+      condition_reg_ |= 2;
+    } else if (!zero_result && overflow) {
+      condition_reg_ |= 1;
+    }
+
+    // We get down here only for floating point

[JoranSiu, 2016/03/31 13:27:57]

Are there any floating point operations that would set the carry flag?  If not,
it might be better to stick an ASSERT to ensure condition_reg_ is non-zero.   

[bcleung, 2016/03/31 19:12:39]

According to principles of operation, no floating-point operations set the carry
flag. This line has been replaced with a check that causes an UNREACHABLE()
error if condition_reg_ is zero.

+    // comparisons and the values are unordered
+    // i.e. NaN
+    if (condition_reg_ == 0) condition_reg_ = unordered;
+  }
+
   bool isNaN(double value) { return (value != value); }
 
   // Set the condition code for bitwise operations