static bool prepareExtraEpilog(SILGenFunction &SGF, JumpDest &dest,
SILLocation &loc, SILValue *arg) {
assert(!SGF.B.hasValidInsertionPoint());
// If we don't have a destination, we don't need to emit the epilog.
if (!dest.isValid())
return false;
// If the destination isn't used, we don't need to emit the epilog.
SILBasicBlock *epilogBB = dest.getBlock();
auto pi = epilogBB->pred_begin(), pe = epilogBB->pred_end();
if (pi == pe) {
dest = JumpDest::invalid();
SGF.eraseBasicBlock(epilogBB);
return false;
}
assert(epilogBB->getNumArguments() <= 1);
assert((epilogBB->getNumArguments() == 1) == (arg != nullptr));
if (arg) *arg = epilogBB->args_begin()[0];
bool reposition = true;
// If the destination has a single branch predecessor,
// consider emitting the epilog into it.
SILBasicBlock *predBB = *pi;
if (++pi == pe) {
if (auto branch = dyn_cast<BranchInst>(predBB->getTerminator())) {
assert(branch->getArgs().size() == epilogBB->getNumArguments());
// Save the location and operand information from the branch,
// then destroy it.
loc = branch->getLoc();
if (arg) *arg = branch->getArgs()[0];
predBB->erase(branch);
// Erase the rethrow block.
SGF.eraseBasicBlock(epilogBB);
epilogBB = predBB;
reposition = false;
}
}
// Reposition the block to the end of the postmatter section
// unless we're emitting into a single predecessor.
if (reposition) {
SGF.B.moveBlockTo(epilogBB, SGF.F.end());
}
SGF.B.setInsertionPoint(epilogBB);
return true;
}
