MIPS: Add float instructions and test coverage, part one

src/mips64/simulator-mips64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <limits.h>
 #include <stdarg.h>
 #include <stdlib.h>
 #include <cmath>
 
 #include "src/v8.h"
@@ skipping 1170 matching lines @@
     FCSR_ &= ~(1 << cc);
   }
 }
 
 
 bool Simulator::test_fcsr_bit(uint32_t cc) {
   return FCSR_ & (1 << cc);
 }
 
 
+void Simulator::set_fcsr_rounding_mode(FPURoundingMode mode) { FCSR_ |= mode; }

[paul.l..., 2015/05/09 01:07:48]

As you did in previous CL for mips32, please use the RoundingModeMask here and
below:
FCSR_ |= mode & kFPURoundingModeMask

[Djordje.Pesic, 2015/05/14 13:22:31]

Done.

+
+
+unsigned int Simulator::get_fcsr_rounding_mode() { return FCSR_ & 0x3; }
+
+
 // Sets the rounding error codes in FCSR based on the result of the rounding.
 // Returns true if the operation was invalid.
 bool Simulator::set_fcsr_round_error(double original, double rounded) {
   bool ret = false;
   double max_int32 = std::numeric_limits<int32_t>::max();
   double min_int32 = std::numeric_limits<int32_t>::min();
 
   if (!std::isfinite(original) || !std::isfinite(rounded)) {
     set_fcsr_bit(kFCSRInvalidOpFlagBit, true);
     ret = true;
   }
 
   if (original != rounded) {
     set_fcsr_bit(kFCSRInexactFlagBit, true);
   }
 
   if (rounded < DBL_MIN && rounded > -DBL_MIN && rounded != 0) {
     set_fcsr_bit(kFCSRUnderflowFlagBit, true);
     ret = true;
   }
 
-  if (rounded > max_int32 || rounded < min_int32) {
+  if (rounded >= max_int32 || rounded <= min_int32) {
     set_fcsr_bit(kFCSROverflowFlagBit, true);
     // The reference is not really clear but it seems this is required:
     set_fcsr_bit(kFCSRInvalidOpFlagBit, true);
     ret = true;
   }
 
   return ret;
 }
 
 
@@ skipping 11 matching lines @@
 
   if (original != rounded) {
     set_fcsr_bit(kFCSRInexactFlagBit, true);
   }
 
   if (rounded < DBL_MIN && rounded > -DBL_MIN && rounded != 0) {
     set_fcsr_bit(kFCSRUnderflowFlagBit, true);
     ret = true;
   }
 
-  if (rounded > max_int64 || rounded < min_int64) {
+  if (rounded >= max_int64 || rounded <= min_int64) {
     set_fcsr_bit(kFCSROverflowFlagBit, true);
     // The reference is not really clear but it seems this is required:
     set_fcsr_bit(kFCSRInvalidOpFlagBit, true);
+    ret = true;
+  }
+
+  return ret;
+}
+
+

[paul.l..., 2015/05/09 01:07:48]

I like the comments that you have on the set_fcsr_round64_error() below, please
add them here as well.

[Djordje.Pesic, 2015/05/14 13:22:31]

Done.

+bool Simulator::set_fcsr_round_error(float original, float rounded) {
+  bool ret = false;
+  double max_int32 = std::numeric_limits<int32_t>::max();
+  double min_int32 = std::numeric_limits<int32_t>::min();
+
+  if (!std::isfinite(original) || !std::isfinite(rounded)) {
+    set_fcsr_bit(kFCSRInvalidOpFlagBit, true);
+    ret = true;
+  }
+
+  if (original != rounded) {
+    set_fcsr_bit(kFCSRInexactFlagBit, true);
+  }
+
+  if (rounded < FLT_MIN && rounded > -FLT_MIN && rounded != 0) {
+    set_fcsr_bit(kFCSRUnderflowFlagBit, true);
+    ret = true;
+  }
+
+  if (rounded >= max_int32 || rounded <= min_int32) {
+    set_fcsr_bit(kFCSROverflowFlagBit, true);
+    // The reference is not really clear but it seems this is required:
+    set_fcsr_bit(kFCSRInvalidOpFlagBit, true);
+    ret = true;
+  }
+
+  return ret;
+}
+
+
+// Sets the rounding error codes in FCSR based on the result of the rounding.
+// Returns true if the operation was invalid.
+bool Simulator::set_fcsr_round64_error(float original, float rounded) {
+  bool ret = false;
+  double max_int64 = std::numeric_limits<int64_t>::max();
+  double min_int64 = std::numeric_limits<int64_t>::min();
+
+  if (!std::isfinite(original) || !std::isfinite(rounded)) {
+    set_fcsr_bit(kFCSRInvalidOpFlagBit, true);
+    ret = true;
+  }
+
+  if (original != rounded) {
+    set_fcsr_bit(kFCSRInexactFlagBit, true);
+  }
+
+  if (rounded < FLT_MIN && rounded > -FLT_MIN && rounded != 0) {
+    set_fcsr_bit(kFCSRUnderflowFlagBit, true);
+    ret = true;
+  }
+
+  if (rounded >= max_int64 || rounded <= min_int64) {
+    set_fcsr_bit(kFCSROverflowFlagBit, true);
+    // The reference is not really clear but it seems this is required:
+    set_fcsr_bit(kFCSRInvalidOpFlagBit, true);
     ret = true;
   }
 
   return ret;
 }
 
 
 // for cvt instructions only
 void Simulator::round_according_to_fcsr(double toRound, double& rounded,
                                         int32_t& rounded_int, double fs) {
@@ skipping 1091 matching lines @@
     default:
       UNREACHABLE();
   }
 }
 
 
 void Simulator::DecodeTypeRegisterSRsType(Instruction* instr,
                                           const int32_t& fs_reg,
                                           const int32_t& ft_reg,
                                           const int32_t& fd_reg) {
-  float fs, ft;
+  float fs, ft, fd;
   fs = get_fpu_register_float(fs_reg);
   ft = get_fpu_register_float(ft_reg);
+  fd = get_fpu_register_float(fd_reg);
+  int32_t ft_int = bit_cast<int32_t>(ft);
+  int32_t fd_int = bit_cast<int32_t>(fd);
   uint32_t cc, fcsr_cc;
   cc = instr->FCccValue();
   fcsr_cc = get_fcsr_condition_bit(cc);
   switch (instr->FunctionFieldRaw()) {
+    case RINT: {
+      DCHECK(kArchVariant == kMips64r6);
+      float result, temp_result;
+      double temp;
+      float upper = std::ceil(fs);
+      float lower = std::floor(fs);
+      switch (get_fcsr_rounding_mode()) {
+        case kRoundToNearest:
+          if (upper - fs < fs - lower) {
+            result = upper;
+          } else if (upper - fs > fs - lower) {
+            result = lower;
+          } else {
+            temp_result = upper / 2;
+            float reminder = modf(temp_result, &temp);
+            if (reminder == 0) {
+              result = upper;
+            } else {
+              result = lower;
+            }
+          }
+          break;
+        case kRoundToZero:
+          result = (fs > 0 ? lower : upper);
+          break;
+        case kRoundToPlusInf:
+          result = upper;
+          break;
+        case kRoundToMinusInf:
+          result = lower;
+          break;
+      }
+      set_fpu_register_float(fd_reg, result);
+      if (result != fs) {
+        set_fcsr_bit(kFCSRInexactFlagBit, true);
+      }
+      break;
+    }
     case ADD_D:
       set_fpu_register_float(fd_reg, fs + ft);
       break;
     case SUB_D:
       set_fpu_register_float(fd_reg, fs - ft);
       break;
     case MUL_D:
       set_fpu_register_float(fd_reg, fs * ft);
       break;
     case DIV_D:
       set_fpu_register_float(fd_reg, fs / ft);
       break;
     case ABS_D:
       set_fpu_register_float(fd_reg, fabs(fs));
       break;
     case MOV_D:
       set_fpu_register_float(fd_reg, fs);
       break;
     case NEG_D:
       set_fpu_register_float(fd_reg, -fs);
       break;
     case SQRT_D:
       set_fpu_register_float(fd_reg, fast_sqrt(fs));
       break;
+    case RSQRT_D: {
+      float result = 1.0 / fast_sqrt(fs);
+      set_fpu_register_float(fd_reg, result);
+      break;
+    }
+    case RECIP: {
+      float result = 1.0 / fs;
+      set_fpu_register_float(fd_reg, result);
+      break;
+    }
     case C_UN_D:
       set_fcsr_bit(fcsr_cc, std::isnan(fs) || std::isnan(ft));
       break;
     case C_EQ_D:
       set_fcsr_bit(fcsr_cc, (fs == ft));
       break;
     case C_UEQ_D:
       set_fcsr_bit(fcsr_cc, (fs == ft) || (std::isnan(fs) || std::isnan(ft)));
       break;
     case C_OLT_D:
       set_fcsr_bit(fcsr_cc, (fs < ft));
       break;
     case C_ULT_D:
       set_fcsr_bit(fcsr_cc, (fs < ft) || (std::isnan(fs) || std::isnan(ft)));
       break;
     case C_OLE_D:
       set_fcsr_bit(fcsr_cc, (fs <= ft));
       break;
     case C_ULE_D:
       set_fcsr_bit(fcsr_cc, (fs <= ft) || (std::isnan(fs) || std::isnan(ft)));
       break;
     case CVT_D_S:
       set_fpu_register_double(fd_reg, static_cast<double>(fs));
       break;
+    case TRUNC_W_S: {  // Truncate single to word (round towards 0).
+      float rounded = trunc(fs);
+      int32_t result = static_cast<int32_t>(rounded);
+      set_fpu_register_word(fd_reg, result);
+      if (set_fcsr_round_error(fs, rounded)) {
+        set_fpu_register_word(fd_reg, kFPUInvalidResult);
+      }
+    } break;
+    case TRUNC_L_S: {
+      float rounded = trunc(fs);
+      int64_t result = static_cast<int64_t>(rounded);
+      set_fpu_register(fd_reg, result);
+      if (set_fcsr_round64_error(fs, rounded)) {
+        set_fpu_register(fd_reg, kFPU64InvalidResult);
+      }
+      break;
+    }
+    case ROUND_W_S: {
+      float rounded = std::floor(fs + 0.5);
+      int32_t result = static_cast<int32_t>(rounded);
+      if ((result & 1) != 0 && result - fs == 0.5) {
+        // If the number is halfway between two integers,
+        // round to the even one.
+        result--;
+      }
+      set_fpu_register_word(fd_reg, result);
+      if (set_fcsr_round_error(fs, rounded)) {
+        set_fpu_register_word(fd_reg, kFPUInvalidResult);
+      }
+      break;
+    }
+    case ROUND_L_S: {  // Mips32r2 instruction.

[paul.l..., 2015/05/09 01:07:48]

mips64r2.

We don't support earlier than mips64r2, so you don't need asserts here, but
please correct the comment.

[Djordje.Pesic, 2015/05/14 13:22:31]

Done.

+      float rounded = std::floor(fs + 0.5);
+      int64_t result = static_cast<int64_t>(rounded);
+      if ((result & 1) != 0 && result - fs == 0.5) {
+        // If the number is halfway between two integers,
+        // round to the even one.
+        result--;
+      }
+      int64_t i64 = static_cast<int64_t>(result);
+      set_fpu_register(fd_reg, i64);
+      if (set_fcsr_round64_error(fs, rounded)) {
+        set_fpu_register(fd_reg, kFPU64InvalidResult);
+      }
+      break;
+    }
+    case FLOOR_L_S: {  // Mips64r2 instruction.
+      float rounded = floor(fs);
+      int64_t result = static_cast<int64_t>(rounded);
+      set_fpu_register(fd_reg, result);
+      if (set_fcsr_round64_error(fs, rounded)) {
+        set_fpu_register(fd_reg, kFPU64InvalidResult);
+      }
+      break;
+    }
+    case FLOOR_W_S:  // Round double to word towards negative infinity.
+    {
+      float rounded = std::floor(fs);
+      int32_t result = static_cast<int32_t>(rounded);
+      set_fpu_register_word(fd_reg, result);
+      if (set_fcsr_round_error(fs, rounded)) {
+        set_fpu_register_word(fd_reg, kFPUInvalidResult);
+      }
+    } break;
+    case CEIL_W_S:  // Round double to word towards positive infinity.
+    {
+      float rounded = std::ceil(fs);
+      int32_t result = static_cast<int32_t>(rounded);
+      set_fpu_register_word(fd_reg, result);
+      if (set_fcsr_round_error(fs, rounded)) {
+        set_fpu_register(fd_reg, kFPUInvalidResult);
+      }
+    } break;
+    case CEIL_L_S: {  // Mips64r2 instruction.
+      float rounded = ceil(fs);
+      int64_t result = static_cast<int64_t>(rounded);
+      set_fpu_register(fd_reg, result);
+      if (set_fcsr_round64_error(fs, rounded)) {
+        set_fpu_register(fd_reg, kFPU64InvalidResult);
+      }
+      break;
+    }
+    case MINA:
+      DCHECK(kArchVariant == kMips64r6);
+      fs = get_fpu_register_float(fs_reg);
+      if (std::isnan(fs) && std::isnan(ft)) {
+        set_fpu_register_float(fd_reg, fs);
+      } else if (std::isnan(fs) && !std::isnan(ft)) {
+        set_fpu_register_float(fd_reg, ft);
+      } else if (!std::isnan(fs) && std::isnan(ft)) {
+        set_fpu_register_float(fd_reg, fs);
+      } else {
+        float result;
+        if (fabs(fs) > fabs(ft)) {
+          result = ft;
+        } else if (fabs(fs) < fabs(ft)) {
+          result = fs;
+        } else {
+          result = (fs > ft ? fs : ft);
+        }
+        set_fpu_register_float(fd_reg, result);
+      }
+      break;
+    case MAXA:
+      DCHECK(kArchVariant == kMips64r6);
+      fs = get_fpu_register_float(fs_reg);
+      if (std::isnan(fs) && std::isnan(ft)) {
+        set_fpu_register_float(fd_reg, fs);
+      } else if (std::isnan(fs) && !std::isnan(ft)) {
+        set_fpu_register_float(fd_reg, ft);
+      } else if (!std::isnan(fs) && std::isnan(ft)) {
+        set_fpu_register_float(fd_reg, fs);
+      } else {
+        float result;
+        if (fabs(fs) < fabs(ft)) {
+          result = ft;
+        } else if (fabs(fs) > fabs(ft)) {
+          result = fs;
+        } else {
+          result = (fs > ft ? fs : ft);
+        }
+        set_fpu_register_float(fd_reg, result);
+      }
+      break;
+    case MIN:
+      DCHECK(kArchVariant == kMips64r6);
+      fs = get_fpu_register_float(fs_reg);
+      if (std::isnan(fs) && std::isnan(ft)) {
+        set_fpu_register_float(fd_reg, fs);
+      } else if (std::isnan(fs) && !std::isnan(ft)) {
+        set_fpu_register_float(fd_reg, ft);
+      } else if (!std::isnan(fs) && std::isnan(ft)) {
+        set_fpu_register_float(fd_reg, fs);
+      } else {
+        set_fpu_register_float(fd_reg, (fs >= ft) ? ft : fs);
+      }
+      break;
+    case MAX:
+      DCHECK(kArchVariant == kMips64r6);
+      fs = get_fpu_register_float(fs_reg);
+      if (std::isnan(fs) && std::isnan(ft)) {
+        set_fpu_register_float(fd_reg, fs);
+      } else if (std::isnan(fs) && !std::isnan(ft)) {
+        set_fpu_register_float(fd_reg, ft);
+      } else if (!std::isnan(fs) && std::isnan(ft)) {
+        set_fpu_register_float(fd_reg, fs);
+      } else {
+        set_fpu_register_float(fd_reg, (fs <= ft) ? ft : fs);
+      }
+      break;
+    case SEL:
+      DCHECK(kArchVariant == kMips64r6);
+      set_fpu_register_float(fd_reg, (fd_int & 0x1) == 0 ? fs : ft);
+      break;
+    case SELEQZ_C:
+      DCHECK(kArchVariant == kMips64r6);
+      set_fpu_register_float(
+          fd_reg, (ft_int & 0x1) == 0 ? get_fpu_register_float(fs_reg) : 0.0);
+      break;
+    case SELNEZ_C:
+      DCHECK(kArchVariant == kMips64r6);
+      set_fpu_register_float(
+          fd_reg, (ft_int & 0x1) != 0 ? get_fpu_register_float(fs_reg) : 0.0);
+      break;
+    case MOVZ_C: {
+      DCHECK(kArchVariant == kMips64r2);
+      int32_t rt_reg = instr->RtValue();
+      int64_t rt = get_register(rt_reg);
+      if (rt == 0) {
+        set_fpu_register_float(fd_reg, fs);
+      }
+      break;
+    }
+    case MOVN_C: {
+      DCHECK(kArchVariant == kMips64r2);
+      int32_t rt_reg = instr->RtValue();
+      int64_t rt = get_register(rt_reg);
+      if (rt != 0) {
+        set_fpu_register_float(fd_reg, fs);
+      }
+      break;
+    }
+    case MOVF: {
+      // Same function field for MOVT.D and MOVF.D
+      uint32_t ft_cc = (ft_reg >> 2) & 0x7;
+      ft_cc = get_fcsr_condition_bit(ft_cc);
+
+      if (instr->Bit(16)) {  // Read Tf bit.
+        // MOVT.D
+        if (test_fcsr_bit(ft_cc)) set_fpu_register_float(fd_reg, fs);
+      } else {
+        // MOVF.D
+        if (!test_fcsr_bit(ft_cc)) set_fpu_register_float(fd_reg, fs);
+      }
+      break;
+    }
     default:
       // CVT_W_S CVT_L_S TRUNC_W_S ROUND_W_S ROUND_L_S FLOOR_W_S FLOOR_L_S
       // CEIL_W_S CEIL_L_S CVT_PS_S are unimplemented.
       UNREACHABLE();
   }
 }
 
 
 void Simulator::DecodeTypeRegisterDRsType(Instruction* instr,
                                           const int32_t& fs_reg,
                                           const int32_t& ft_reg,
                                           const int32_t& fd_reg) {
   double ft, fs, fd;
   uint32_t cc, fcsr_cc;
   fs = get_fpu_register_double(fs_reg);
-  ft = get_fpu_register_double(ft_reg);
+  if (instr->FunctionFieldRaw() != MOVF) {
+    ft = get_fpu_register_double(ft_reg);
+  }
   fd = get_fpu_register_double(fd_reg);
   cc = instr->FCccValue();
   fcsr_cc = get_fcsr_condition_bit(cc);
   int64_t ft_int = bit_cast<int64_t>(ft);
   int64_t fd_int = bit_cast<int64_t>(fd);
   switch (instr->FunctionFieldRaw()) {
     case RINT: {
       DCHECK(kArchVariant == kMips64r6);
       double result, temp, temp_result;
       double upper = std::ceil(fs);
       double lower = std::floor(fs);
-      switch (FCSR_ & 0x3) {
+      switch (get_fcsr_rounding_mode()) {
         case kRoundToNearest:
           if (upper - fs < fs - lower) {
             result = upper;
           } else if (upper - fs > fs - lower) {
             result = lower;
           } else {
             temp_result = upper / 2;
             double reminder = modf(temp_result, &temp);
             if (reminder == 0) {
               result = upper;
@@ skipping 23 matching lines @@
       set_fpu_register_double(fd_reg, (fd_int & 0x1) == 0 ? fs : ft);
       break;
     case SELEQZ_C:
       DCHECK(kArchVariant == kMips64r6);
       set_fpu_register_double(fd_reg, (ft_int & 0x1) == 0 ? fs : 0.0);
       break;
     case SELNEZ_C:
       DCHECK(kArchVariant == kMips64r6);
       set_fpu_register_double(fd_reg, (ft_int & 0x1) != 0 ? fs : 0.0);
       break;
+    case MOVZ_C: {
+      DCHECK(kArchVariant == kMips64r2);
+      int32_t rt_reg = instr->RtValue();
+      int64_t rt = get_register(rt_reg);
+      if (rt == 0) {
+        set_fpu_register_double(fd_reg, fs);
+      }
+      break;
+    }
+    case MOVN_C: {
+      DCHECK(kArchVariant == kMips64r2);
+      int32_t rt_reg = instr->RtValue();
+      int64_t rt = get_register(rt_reg);
+      if (rt != 0) {
+        set_fpu_register_double(fd_reg, fs);
+      }
+      break;
+    }
+    case MOVF: {
+      // Same function field for MOVT.D and MOVF.D
+      uint32_t ft_cc = (ft_reg >> 2) & 0x7;
+      ft_cc = get_fcsr_condition_bit(ft_cc);
+      if (instr->Bit(16)) {  // Read Tf bit.
+        // MOVT.D
+        if (test_fcsr_bit(ft_cc)) set_fpu_register_double(fd_reg, fs);
+      } else {
+        // MOVF.D
+        if (!test_fcsr_bit(ft_cc)) set_fpu_register_double(fd_reg, fs);
+      }
+      break;
+    }
+    case MINA:
+      DCHECK(kArchVariant == kMips64r6);
+      fs = get_fpu_register_double(fs_reg);
+      if (std::isnan(fs) && std::isnan(ft)) {
+        set_fpu_register_double(fd_reg, fs);
+      } else if (std::isnan(fs) && !std::isnan(ft)) {
+        set_fpu_register_double(fd_reg, ft);
+      } else if (!std::isnan(fs) && std::isnan(ft)) {
+        set_fpu_register_double(fd_reg, fs);
+      } else {
+        double result;
+        if (fabs(fs) > fabs(ft)) {
+          result = ft;
+        } else if (fabs(fs) < fabs(ft)) {
+          result = fs;
+        } else {
+          result = (fs > ft ? fs : ft);
+        }
+        set_fpu_register_double(fd_reg, result);
+      }
+      break;
+    case MAXA:
+      DCHECK(kArchVariant == kMips64r6);
+      fs = get_fpu_register_double(fs_reg);
+      if (std::isnan(fs) && std::isnan(ft)) {
+        set_fpu_register_double(fd_reg, fs);
+      } else if (std::isnan(fs) && !std::isnan(ft)) {
+        set_fpu_register_double(fd_reg, ft);
+      } else if (!std::isnan(fs) && std::isnan(ft)) {
+        set_fpu_register_double(fd_reg, fs);
+      } else {
+        double result;
+        if (fabs(fs) < fabs(ft)) {
+          result = ft;
+        } else if (fabs(fs) > fabs(ft)) {
+          result = fs;
+        } else {
+          result = (fs > ft ? fs : ft);
+        }
+        set_fpu_register_double(fd_reg, result);
+      }
+      break;
     case MIN:
       DCHECK(kArchVariant == kMips64r6);
       fs = get_fpu_register_double(fs_reg);
       if (std::isnan(fs) && std::isnan(ft)) {
         set_fpu_register_double(fd_reg, fs);
       } else if (std::isnan(fs) && !std::isnan(ft)) {
         set_fpu_register_double(fd_reg, ft);
       } else if (!std::isnan(fs) && std::isnan(ft)) {
         set_fpu_register_double(fd_reg, fs);
       } else {
@@ skipping 30 matching lines @@
       break;
     case MOV_D:
       set_fpu_register_double(fd_reg, fs);
       break;
     case NEG_D:
       set_fpu_register_double(fd_reg, -fs);
       break;
     case SQRT_D:
       set_fpu_register_double(fd_reg, fast_sqrt(fs));
       break;
+    case RSQRT_D: {
+      double result = 1.0 / fast_sqrt(fs);
+      set_fpu_register_double(fd_reg, result);
+      break;
+    }
+    case RECIP: {
+      double result = 1.0 / fs;
+      set_fpu_register_double(fd_reg, result);
+      break;
+    }
     case C_UN_D:
       set_fcsr_bit(fcsr_cc, std::isnan(fs) || std::isnan(ft));
       break;
     case C_EQ_D:
       set_fcsr_bit(fcsr_cc, (fs == ft));
       break;
     case C_UEQ_D:
       set_fcsr_bit(fcsr_cc, (fs == ft) || (std::isnan(fs) || std::isnan(ft)));
       break;
     case C_OLT_D:
@@ skipping 66 matching lines @@
       double rounded;
       int64_t result;
       round64_according_to_fcsr(fs, rounded, result, fs);
       set_fpu_register(fd_reg, result);
       if (set_fcsr_round64_error(fs, rounded)) {
         set_fpu_register(fd_reg, kFPUInvalidResult);
       }
       break;
     }
     case ROUND_L_D: {  // Mips64r2 instruction.
-      // check error cases
-      double rounded = fs > 0 ? floor(fs + 0.5) : ceil(fs - 0.5);
+      double rounded = std::floor(fs + 0.5);
       int64_t result = static_cast<int64_t>(rounded);
-      set_fpu_register(fd_reg, result);
+      if ((result & 1) != 0 && result - fs == 0.5) {
+        // If the number is halfway between two integers,
+        // round to the even one.
+        result--;
+      }
+      int64_t i64 = static_cast<int64_t>(result);
+      set_fpu_register(fd_reg, i64);
       if (set_fcsr_round64_error(fs, rounded)) {
         set_fpu_register(fd_reg, kFPU64InvalidResult);
       }
       break;
     }
     case TRUNC_L_D: {  // Mips64r2 instruction.
       double rounded = trunc(fs);
       int64_t result = static_cast<int64_t>(rounded);
       set_fpu_register(fd_reg, result);
       if (set_fcsr_round64_error(fs, rounded)) {
@@ skipping 1116 matching lines @@
   return address;
 }
 
 
 #undef UNSUPPORTED
 } }  // namespace v8::internal
 
 #endif  // USE_SIMULATOR
 
 #endif  // V8_TARGET_ARCH_MIPS64