dfg/DFGArithMode.h

   1 /*
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  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  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 } // namespace Arith
  44
  45 inline bool doesOverflow(Arith::Mode mode)
  46 {
  47     switch (mode) {
  48     case Arith::NotSet:
  49         ASSERT_NOT_REACHED();
  50 #if ASSERT_DISABLED
  51         FALLTHROUGH;
  52 #endif
  53     case Arith::Unchecked:
  54     case Arith::CheckOverflow:
  55     case Arith::CheckOverflowAndNegativeZero:
  56         return false;
  57     case Arith::DoOverflow:
  58         return true;
  59     }
  60     ASSERT_NOT_REACHED();
  61     return true;
  62 }
  63
  64 // It's only valid to call this once you've determined that you don't need to *do*
  65 // overflow. For most nodes, that's implicit.
  66 inline bool shouldCheckOverflow(Arith::Mode mode)
  67 {
  68     switch (mode) {
  69     case Arith::NotSet:
  70     case Arith::DoOverflow:
  71         ASSERT_NOT_REACHED();
  72         return true;
  73     case Arith::Unchecked:
  74         return false;
  75     case Arith::CheckOverflow:
  76     case Arith::CheckOverflowAndNegativeZero:
  77         return true;
  78     }
  79     ASSERT_NOT_REACHED();
  80     return true;
  81 }
  82
  83 inline bool shouldCheckNegativeZero(Arith::Mode mode)
  84 {
  85     switch (mode) {
  86     case Arith::NotSet:
  87     case Arith::DoOverflow:
  88         ASSERT_NOT_REACHED();
  89         return true;
  90     case Arith::Unchecked:
  91     case Arith::CheckOverflow:
  92         return false;
  93     case Arith::CheckOverflowAndNegativeZero:
  94         return true;
  95     }
  96     ASSERT_NOT_REACHED();
  97     return true;
  98 }
  99
 100 inline bool subsumes(Arith::Mode earlier, Arith::Mode later)
 101 {
 102     switch (earlier) {
 103     case Arith::CheckOverflow:
 104         switch (later) {
 105         case Arith::Unchecked:
 106         case Arith::CheckOverflow:
 107             return true;
 108         default:
 109             return false;
 110         }
 111     case Arith::CheckOverflowAndNegativeZero:
 112         switch (later) {
 113         case Arith::Unchecked:
 114         case Arith::CheckOverflow:
 115         case Arith::CheckOverflowAndNegativeZero:
 116             return true;
 117         default:
 118             return false;
 119         }
 120     default:
 121         return earlier == later;
 122     }
 123 }
 124
 125 } } // namespace JSC::DFG
 126
 127 namespace WTF {
 128
 129 class PrintStream;
 130 void printInternal(PrintStream&, JSC::DFG::Arith::Mode);
 131
 132 } // namespace WTF
 133
 134 #endif // ENABLE(DFG_JIT)
 135
 136 #endif // DFGArithMode_h
 137