+ /// isTransient - Return true if this is a transient instruction that is
+ /// either very likely to be eliminated during register allocation (such as
+ /// copy-like instructions), or if this instruction doesn't have an
+ /// execution-time cost.
+ bool isTransient() const {
+ switch(getOpcode()) {
+ default: return false;
+ // Copy-like instructions are usually eliminated during register allocation.
+ case TargetOpcode::PHI:
+ case TargetOpcode::COPY:
+ case TargetOpcode::INSERT_SUBREG:
+ case TargetOpcode::SUBREG_TO_REG:
+ case TargetOpcode::REG_SEQUENCE:
+ // Pseudo-instructions that don't produce any real output.
+ case TargetOpcode::IMPLICIT_DEF:
+ case TargetOpcode::KILL:
+ case TargetOpcode::PROLOG_LABEL:
+ case TargetOpcode::EH_LABEL:
+ case TargetOpcode::GC_LABEL:
+ case TargetOpcode::DBG_VALUE:
+ return true;
+ }
+ }
+