dfg/DFGArithMode.h

   1 /*
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  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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  25
  26 #ifndef DFGArithMode_h
  27 #define DFGArithMode_h
  28
  29 #if ENABLE(DFG_JIT)
  30
  31 namespace JSC { namespace DFG {
  32
  33 // Arith::Mode describes the mode of an arithmetic operation that speculates integer.
  34 // Note that not all modes are valid for all operations.
  35 namespace Arith {
  36 enum Mode {
  37     NotSet, // Arithmetic mode is either not relevant because we're using doubles anyway or we are at a phase in compilation where we don't know what we're doing, yet. Should never see this after FixupPhase except for nodes that take doubles as inputs already.
  38     Unchecked, // Don't check anything and just do the direct hardware operation.
  39     CheckOverflow, // Check for overflow but don't bother with negative zero.
  40     CheckOverflowAndNegativeZero, // Check for both overflow and negative zero.
  41     DoOverflow // Up-convert to the smallest type that soundly represents all possible results after input type speculation.
  42 };
  43
  44 // Define the type of operation the rounding operation will perform.
  45 enum class RoundingMode {
  46     Int32, // The round operation produces a integer and -0 is considered as 0.
  47     Int32WithNegativeZeroCheck, // The round operation produces a integer and checks for -0.
  48     Double // The round operation produce a double. The result can be -0, NaN or (+/-)Infinity.
  49 };
  50
  51 } // namespace Arith
  52
  53 inline bool doesOverflow(Arith::Mode mode)
  54 {
  55     switch (mode) {
  56     case Arith::NotSet:
  57         ASSERT_NOT_REACHED();
  58 #if ASSERT_DISABLED
  59         FALLTHROUGH;
  60 #endif
  61     case Arith::Unchecked:
  62     case Arith::CheckOverflow:
  63     case Arith::CheckOverflowAndNegativeZero:
  64         return false;
  65     case Arith::DoOverflow:
  66         return true;
  67     }
  68     ASSERT_NOT_REACHED();
  69     return true;
  70 }
  71
  72 // It's only valid to call this once you've determined that you don't need to *do*
  73 // overflow. For most nodes, that's implicit.
  74 inline bool shouldCheckOverflow(Arith::Mode mode)
  75 {
  76     switch (mode) {
  77     case Arith::NotSet:
  78     case Arith::DoOverflow:
  79         ASSERT_NOT_REACHED();
  80         return true;
  81     case Arith::Unchecked:
  82         return false;
  83     case Arith::CheckOverflow:
  84     case Arith::CheckOverflowAndNegativeZero:
  85         return true;
  86     }
  87     ASSERT_NOT_REACHED();
  88     return true;
  89 }
  90
  91 inline bool shouldCheckNegativeZero(Arith::Mode mode)
  92 {
  93     switch (mode) {
  94     case Arith::NotSet:
  95     case Arith::DoOverflow:
  96         ASSERT_NOT_REACHED();
  97         return true;
  98     case Arith::Unchecked:
  99     case Arith::CheckOverflow:
 100         return false;
 101     case Arith::CheckOverflowAndNegativeZero:
 102         return true;
 103     }
 104     ASSERT_NOT_REACHED();
 105     return true;
 106 }
 107
 108 inline bool subsumes(Arith::Mode earlier, Arith::Mode later)
 109 {
 110     switch (earlier) {
 111     case Arith::CheckOverflow:
 112         switch (later) {
 113         case Arith::Unchecked:
 114         case Arith::CheckOverflow:
 115             return true;
 116         default:
 117             return false;
 118         }
 119     case Arith::CheckOverflowAndNegativeZero:
 120         switch (later) {
 121         case Arith::Unchecked:
 122         case Arith::CheckOverflow:
 123         case Arith::CheckOverflowAndNegativeZero:
 124             return true;
 125         default:
 126             return false;
 127         }
 128     default:
 129         return earlier == later;
 130     }
 131 }
 132
 133 inline bool producesInteger(Arith::RoundingMode mode)
 134 {
 135     return mode == Arith::RoundingMode::Int32WithNegativeZeroCheck || mode == Arith::RoundingMode::Int32;
 136 }
 137
 138 inline bool shouldCheckNegativeZero(Arith::RoundingMode mode)
 139 {
 140     return mode == Arith::RoundingMode::Int32WithNegativeZeroCheck;
 141 }
 142
 143 } } // namespace JSC::DFG
 144
 145 namespace WTF {
 146
 147 class PrintStream;
 148 void printInternal(PrintStream&, JSC::DFG::Arith::Mode);
 149
 150 } // namespace WTF
 151
 152 #endif // ENABLE(DFG_JIT)
 153
 154 #endif // DFGArithMode_h
 155