diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Target/Target.td | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/lib/Target/Target.td b/lib/Target/Target.td index 9619cb98f9..a9438a7a5e 100644 --- a/lib/Target/Target.td +++ b/lib/Target/Target.td @@ -205,9 +205,18 @@ class Instruction { bit isNotDuplicable = 0; // Is it unsafe to duplicate this instruction? // Side effect flags - If neither of these flags is set, then the instruction - // *always* has side effects. Otherwise, it's one or the other. - bit mayHaveSideEffects = 0; // This instruction *may* have side effects. - bit neverHasSideEffects = 0; // This instruction never has side effects. + // *always* has side effects. When set, the flags have these meanings: + // + // neverHasSideEffects - The instruction has no side effects that are not + // captured by any operands of the instruction or other flags, and when + // *all* instances of the instruction of that opcode have no side effects. + // mayHaveSideEffects - Some instances of the instruction can have side + // effects. The virtual method "isReallySideEffectFree" is called to + // determine this. Load instructions are an example of where this is + // useful. In general, loads always have side effects. However, loads from + // constant pools don't. Individual back ends make this determination. + bit neverHasSideEffects = 0; + bit mayHaveSideEffects = 0; InstrItinClass Itinerary = NoItinerary;// Execution steps used for scheduling. |