Reland "MIPS: Add float instructions and test coverage, part one"

src/mips/simulator-mips.cc

Index: src/mips/simulator-mips.cc
diff --git a/src/mips/simulator-mips.cc b/src/mips/simulator-mips.cc
index 68fbdae96ee015d27ff33ae1ddaf0eed651b03a9..cb4ecc108d639c2c5ce499e37aed79ea457dec20 100644
--- a/src/mips/simulator-mips.cc
+++ b/src/mips/simulator-mips.cc
@@ -1282,8 +1282,6 @@ unsigned int Simulator::get_fcsr_rounding_mode() {
 }
 
 
-// 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();
@@ -1314,6 +1312,100 @@ bool Simulator::set_fcsr_round_error(double original, double rounded) {
 }
 
 
+// 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(double original, double 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 < DBL_MIN && rounded > -DBL_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;
+}
+
+
+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;
+}
+
+
 void Simulator::round_according_to_fcsr(double toRound, double& rounded,
                                         int32_t& rounded_int, double fs) {
   // 0 RN (round to nearest): Round a result to the nearest
@@ -2191,7 +2283,10 @@ void Simulator::DecodeTypeRegisterDRsType(Instruction* instr,
   uint32_t cc, fcsr_cc;
   int64_t i64;
   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);
   int64_t ft_int = bit_cast<int64_t>(ft);
   int64_t fd_int = bit_cast<int64_t>(fd);
   cc = instr->FCccValue();
@@ -2246,6 +2341,37 @@ void Simulator::DecodeTypeRegisterDRsType(Instruction* instr,
       DCHECK(IsMipsArchVariant(kMips32r6));
       set_fpu_register_double(fd_reg, (ft_int & 0x1) != 0 ? fs : 0.0);
       break;
+    case MOVZ_C: {
+      DCHECK(IsMipsArchVariant(kMips32r2));
+      int32_t rt_reg = instr->RtValue();
+      int32_t rt = get_register(rt_reg);
+      if (rt == 0) {
+        set_fpu_register_double(fd_reg, fs);
+      }
+      break;
+    }
+    case MOVN_C: {
+      DCHECK(IsMipsArchVariant(kMips32r2));
+      int32_t rt_reg = instr->RtValue();
+      int32_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 MIN:
       DCHECK(IsMipsArchVariant(kMips32r6));
       fs = get_fpu_register_double(fs_reg);
@@ -2259,6 +2385,48 @@ void Simulator::DecodeTypeRegisterDRsType(Instruction* instr,
         set_fpu_register_double(fd_reg, (fs >= ft) ? ft : fs);
       }
       break;
+    case MINA:
+      DCHECK(IsMipsArchVariant(kMips32r6));
+      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(IsMipsArchVariant(kMips32r6));
+      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 MAX:
       DCHECK(IsMipsArchVariant(kMips32r6));
       fs = get_fpu_register_double(fs_reg);
@@ -2297,6 +2465,16 @@ void Simulator::DecodeTypeRegisterDRsType(Instruction* instr,
     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_D: {
+      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;
@@ -2377,51 +2555,72 @@ void Simulator::DecodeTypeRegisterDRsType(Instruction* instr,
       if (IsFp64Mode()) {
         set_fpu_register(fd_reg, i64);
       } else {
-        set_fpu_register_word(fd_reg, i64 & 0xffffffff);
-        set_fpu_register_word(fd_reg + 1, i64 >> 32);
+        UNSUPPORTED();
       }
       break;
     }
     case TRUNC_L_D: {  // Mips32r2 instruction.
+      DCHECK(IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6));
       double rounded = trunc(fs);
       i64 = static_cast<int64_t>(rounded);
       if (IsFp64Mode()) {
         set_fpu_register(fd_reg, i64);
+        if (set_fcsr_round64_error(fs, rounded)) {
+          set_fpu_register(fd_reg, kFPU64InvalidResult);
+        }
       } else {
-        set_fpu_register_word(fd_reg, i64 & 0xffffffff);
-        set_fpu_register_word(fd_reg + 1, i64 >> 32);
+        UNSUPPORTED();
       }
       break;
     }
     case ROUND_L_D: {  // Mips32r2 instruction.
-      double rounded = fs > 0 ? std::floor(fs + 0.5) : std::ceil(fs - 0.5);
-      i64 = static_cast<int64_t>(rounded);
+      DCHECK(IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6));
+      double 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);
       if (IsFp64Mode()) {
         set_fpu_register(fd_reg, i64);
+        if (set_fcsr_round64_error(fs, rounded)) {
+          set_fpu_register(fd_reg, kFPU64InvalidResult);
+        }
       } else {
-        set_fpu_register_word(fd_reg, i64 & 0xffffffff);
-        set_fpu_register_word(fd_reg + 1, i64 >> 32);
+        UNSUPPORTED();
       }
       break;
     }
-    case FLOOR_L_D:  // Mips32r2 instruction.
-      i64 = static_cast<int64_t>(std::floor(fs));
+    case FLOOR_L_D: {  // Mips32r2 instruction.
+      DCHECK(IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6));
+      double rounded = std::floor(fs);
+      int64_t i64 = static_cast<int64_t>(rounded);
       if (IsFp64Mode()) {
         set_fpu_register(fd_reg, i64);
+        if (set_fcsr_round64_error(fs, rounded)) {
+          set_fpu_register(fd_reg, kFPU64InvalidResult);
+        }
       } else {
-        set_fpu_register_word(fd_reg, i64 & 0xffffffff);
-        set_fpu_register_word(fd_reg + 1, i64 >> 32);
+        UNSUPPORTED();
       }
       break;
-    case CEIL_L_D:  // Mips32r2 instruction.
-      i64 = static_cast<int64_t>(std::ceil(fs));
+    }
+    case CEIL_L_D: {  // Mips32r2 instruction.
+      DCHECK(IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6));
+      double rounded = std::ceil(fs);
+      int64_t i64 = static_cast<int64_t>(rounded);
       if (IsFp64Mode()) {
         set_fpu_register(fd_reg, i64);
+        if (set_fcsr_round64_error(fs, rounded)) {
+          set_fpu_register(fd_reg, kFPU64InvalidResult);
+        }
       } else {
-        set_fpu_register_word(fd_reg, i64 & 0xffffffff);
-        set_fpu_register_word(fd_reg + 1, i64 >> 32);
+        UNSUPPORTED();
       }
       break;
+    }
     case C_F_D:
       UNIMPLEMENTED_MIPS();
       break;
@@ -2453,38 +2652,88 @@ void Simulator::DecodeTypeRegisterSRsType(Instruction* instr,
                                           const int32_t& ft_reg,
                                           const int32_t& fs_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);
-  int64_t ft_int = static_cast<int64_t>(get_fpu_register_double(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 ADD_D:
+    case RINT: {
+      DCHECK(IsMipsArchVariant(kMips32r6));
+      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_S:
       set_fpu_register_float(fd_reg, fs + ft);
       break;
-    case SUB_D:
+    case SUB_S:
       set_fpu_register_float(fd_reg, fs - ft);
       break;
-    case MUL_D:
+    case MUL_S:
       set_fpu_register_float(fd_reg, fs * ft);
       break;
-    case DIV_D:
+    case DIV_S:
       set_fpu_register_float(fd_reg, fs / ft);
       break;
-    case ABS_D:
+    case ABS_S:
       set_fpu_register_float(fd_reg, fabs(fs));
       break;
-    case MOV_D:
+    case MOV_S:
       set_fpu_register_float(fd_reg, fs);
       break;
-    case NEG_D:
+    case NEG_S:
       set_fpu_register_float(fd_reg, -fs);
       break;
-    case SQRT_D:
+    case SQRT_S:
       set_fpu_register_float(fd_reg, fast_sqrt(fs));
       break;
+    case RSQRT_S: {
+      float result = 1.0 / fast_sqrt(fs);
+      set_fpu_register_float(fd_reg, result);
+      break;
+    }
+    case RECIP_S: {
+      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;
@@ -2509,18 +2758,224 @@ void Simulator::DecodeTypeRegisterSRsType(Instruction* instr,
     case CVT_D_S:
       set_fpu_register_double(fd_reg, static_cast<double>(fs));
       break;
+    case SEL:
+      DCHECK(IsMipsArchVariant(kMips32r6));
+      set_fpu_register_float(fd_reg, (fd_int & 0x1) == 0 ? fs : ft);
+      break;
     case SELEQZ_C:
       DCHECK(IsMipsArchVariant(kMips32r6));
-      set_fpu_register_double(
-          fd_reg, (ft_int & 0x1) == 0 ? get_fpu_register_double(fs_reg) : 0.0);
+      set_fpu_register_float(
+          fd_reg, (ft_int & 0x1) == 0 ? get_fpu_register_float(fs_reg) : 0.0);
       break;
     case SELNEZ_C:
       DCHECK(IsMipsArchVariant(kMips32r6));
-      set_fpu_register_double(
-          fd_reg, (ft_int & 0x1) != 0 ? get_fpu_register_double(fs_reg) : 0.0);
+      set_fpu_register_float(
+          fd_reg, (ft_int & 0x1) != 0 ? get_fpu_register_float(fs_reg) : 0.0);
+      break;
+    case MOVZ_C: {
+      DCHECK(IsMipsArchVariant(kMips32r2));
+      int32_t rt_reg = instr->RtValue();
+      int32_t rt = get_register(rt_reg);
+      if (rt == 0) {
+        set_fpu_register_float(fd_reg, fs);
+      }
+      break;
+    }
+    case MOVN_C: {
+      DCHECK(IsMipsArchVariant(kMips32r2));
+      int32_t rt_reg = instr->RtValue();
+      int32_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;
+    }
+    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: {  // Mips32r2 instruction.
+      DCHECK(IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6));
+      float rounded = trunc(fs);
+      int64_t i64 = static_cast<int64_t>(rounded);
+      if (IsFp64Mode()) {
+        set_fpu_register(fd_reg, i64);
+        if (set_fcsr_round64_error(fs, rounded)) {
+          set_fpu_register(fd_reg, kFPU64InvalidResult);
+        }
+      } else {
+        UNSUPPORTED();
+      }
+      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 FLOOR_L_S: {  // Mips32r2 instruction.
+      DCHECK(IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6));
+      float rounded = std::floor(fs);
+      int64_t i64 = static_cast<int64_t>(rounded);
+      if (IsFp64Mode()) {
+        set_fpu_register(fd_reg, i64);
+        if (set_fcsr_round64_error(fs, rounded)) {
+          set_fpu_register(fd_reg, kFPU64InvalidResult);
+        }
+      } else {
+        UNSUPPORTED();
+      }
+      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.
+      DCHECK(IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6));
+      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);
+      if (IsFp64Mode()) {
+        set_fpu_register(fd_reg, i64);
+        if (set_fcsr_round64_error(fs, rounded)) {
+          set_fpu_register(fd_reg, kFPU64InvalidResult);
+        }
+      } else {
+        UNSUPPORTED();
+      }
+      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_word(fd_reg, kFPUInvalidResult);
+      }
+    } break;
+    case CEIL_L_S: {  // Mips32r2 instruction.
+      DCHECK(IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6));
+      float rounded = std::ceil(fs);
+      int64_t i64 = static_cast<int64_t>(rounded);
+      if (IsFp64Mode()) {
+        set_fpu_register(fd_reg, i64);
+        if (set_fcsr_round64_error(fs, rounded)) {
+          set_fpu_register(fd_reg, kFPU64InvalidResult);
+        }
+      } else {
+        UNSUPPORTED();
+      }
+      break;
+    }
+    case MIN:
+      DCHECK(IsMipsArchVariant(kMips32r6));
+      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(IsMipsArchVariant(kMips32r6));
+      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 MINA:
+      DCHECK(IsMipsArchVariant(kMips32r6));
+      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(IsMipsArchVariant(kMips32r6));
+      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;
     default:
-      // CVT_W_S CVT_L_S TRUNC_W_S ROUND_W_S ROUND_L_S FLOOR_W_S FLOOR_L_S
+      // CVT_W_S CVT_L_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();
   }