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;
}
void SILGenFunction::emitRethrowEpilog(SILLocation topLevel) {
assert(!B.hasValidInsertionPoint());
// If we don't have a rethrow destination, we're done.
if (!ThrowDest.isValid())
return;
// If the rethrow destination isn't used, we're done.
SILBasicBlock *rethrowBB = ThrowDest.getBlock();
if (rethrowBB->pred_empty()) {
ThrowDest = JumpDest::invalid();
eraseBasicBlock(rethrowBB);
return;
}
SILLocation throwLoc = topLevel;
SILValue exn = rethrowBB->bbarg_begin()[0];
bool reposition = true;
// If the rethrow destination has a single branch predecessor,
// consider emitting the rethrow into it.
SILBasicBlock *predBB = *rethrowBB->pred_begin();
if (std::next(rethrowBB->pred_begin()) == rethrowBB->pred_end()) {
if (auto branch = dyn_cast<BranchInst>(predBB->getTerminator())) {
assert(branch->getArgs().size() == 1);
// Save the location and operand information from the branch,
// then destroy it.
throwLoc = branch->getLoc();
exn = branch->getArgs()[0];
predBB->erase(branch);
// Erase the rethrow block.
eraseBasicBlock(rethrowBB);
rethrowBB = predBB;
reposition = false;
}
}
// Reposition the rethrow block to the end of the postmatter section
// unless we're emitting into a single predecessor.
if (reposition) {
B.moveBlockTo(rethrowBB, F.end());
}
B.setInsertionPoint(rethrowBB);
Cleanups.emitCleanupsForReturn(ThrowDest.getCleanupLocation());
B.createThrow(throwLoc, exn);
ThrowDest = JumpDest::invalid();
}
std::pair<Optional<SILValue>, SILLocation>
SILGenFunction::emitEpilogBB(SILLocation TopLevel) {
assert(ReturnDest.getBlock() && "no epilog bb prepared?!");
SILBasicBlock *epilogBB = ReturnDest.getBlock();
SILLocation ImplicitReturnFromTopLevel =
ImplicitReturnLocation::getImplicitReturnLoc(TopLevel);
SmallVector<SILValue, 4> directResults;
Optional<SILLocation> returnLoc = None;
// If the current BB isn't terminated, and we require a return, then we
// are not allowed to fall off the end of the function and can't reach here.
if (NeedsReturn && B.hasValidInsertionPoint())
B.createUnreachable(ImplicitReturnFromTopLevel);
if (epilogBB->pred_empty()) {
// If the epilog was not branched to at all, kill the BB and
// just emit the epilog into the current BB.
while (!epilogBB->empty())
epilogBB->back().eraseFromParent();
eraseBasicBlock(epilogBB);
// If the current bb is terminated then the epilog is just unreachable.
if (!B.hasValidInsertionPoint())
return { None, TopLevel };
// We emit the epilog at the current insertion point.
returnLoc = ImplicitReturnFromTopLevel;
} else if (std::next(epilogBB->pred_begin()) == epilogBB->pred_end()
&& !B.hasValidInsertionPoint()) {
// If the epilog has a single predecessor and there's no current insertion
// point to fall through from, then we can weld the epilog to that
// predecessor BB.
// Steal the branch argument as the return value if present.
SILBasicBlock *pred = *epilogBB->pred_begin();
BranchInst *predBranch = cast<BranchInst>(pred->getTerminator());
assert(predBranch->getArgs().size() == epilogBB->bbarg_size() &&
"epilog predecessor arguments does not match block params");
for (auto index : indices(predBranch->getArgs())) {
SILValue result = predBranch->getArgs()[index];
directResults.push_back(result);
epilogBB->getBBArg(index)->replaceAllUsesWith(result);
}
// If we are optimizing, we should use the return location from the single,
// previously processed, return statement if any.
if (predBranch->getLoc().is<ReturnLocation>()) {
returnLoc = predBranch->getLoc();
} else {
returnLoc = ImplicitReturnFromTopLevel;
}
// Kill the branch to the now-dead epilog BB.
pred->erase(predBranch);
// Move any instructions from the EpilogBB to the end of the 'pred' block.
pred->spliceAtEnd(epilogBB);
// Finally we can erase the epilog BB.
eraseBasicBlock(epilogBB);
// Emit the epilog into its former predecessor.
B.setInsertionPoint(pred);
} else {
// Move the epilog block to the end of the ordinary section.
auto endOfOrdinarySection = StartOfPostmatter;
B.moveBlockTo(epilogBB, endOfOrdinarySection);
// Emit the epilog into the epilog bb. Its arguments are the
// direct results.
directResults.append(epilogBB->bbarg_begin(), epilogBB->bbarg_end());
// If we are falling through from the current block, the return is implicit.
B.emitBlock(epilogBB, ImplicitReturnFromTopLevel);
}
// Emit top-level cleanups into the epilog block.
assert(!Cleanups.hasAnyActiveCleanups(getCleanupsDepth(),
ReturnDest.getDepth()) &&
"emitting epilog in wrong scope");
auto cleanupLoc = CleanupLocation::get(TopLevel);
Cleanups.emitCleanupsForReturn(cleanupLoc);
// If the return location is known to be that of an already
// processed return, use it. (This will get triggered when the
// epilog logic is simplified.)
//
// Otherwise make the ret instruction part of the cleanups.
if (!returnLoc) returnLoc = cleanupLoc;
// Build the return value. We don't do this if there are no direct
// results; this can happen for void functions, but also happens when
// prepareEpilog was asked to not add result arguments to the epilog
// block.
SILValue returnValue;
if (!directResults.empty()) {
assert(directResults.size()
== F.getLoweredFunctionType()->getNumDirectResults());
returnValue = buildReturnValue(*this, TopLevel, directResults);
}
return { returnValue, *returnLoc };
}
std::pair<Optional<SILValue>, SILLocation>
SILGenFunction::emitEpilogBB(SILLocation TopLevel) {
assert(ReturnDest.getBlock() && "no epilog bb prepared?!");
SILBasicBlock *epilogBB = ReturnDest.getBlock();
SILLocation ImplicitReturnFromTopLevel =
ImplicitReturnLocation::getImplicitReturnLoc(TopLevel);
SILValue returnValue;
Optional<SILLocation> returnLoc = None;
// If the current BB isn't terminated, and we require a return, then we
// are not allowed to fall off the end of the function and can't reach here.
if (NeedsReturn && B.hasValidInsertionPoint())
B.createUnreachable(ImplicitReturnFromTopLevel);
if (epilogBB->pred_empty()) {
bool hadArg = !epilogBB->bbarg_empty();
// If the epilog was not branched to at all, kill the BB and
// just emit the epilog into the current BB.
while (!epilogBB->empty())
epilogBB->back().eraseFromParent();
eraseBasicBlock(epilogBB);
// If the current bb is terminated then the epilog is just unreachable.
if (!B.hasValidInsertionPoint())
return { None, TopLevel };
// We emit the epilog at the current insertion point.
assert(!hadArg && "NeedsReturn is false but epilog had argument?!");
(void)hadArg;
returnLoc = ImplicitReturnFromTopLevel;
} else if (std::next(epilogBB->pred_begin()) == epilogBB->pred_end()
&& !B.hasValidInsertionPoint()) {
// If the epilog has a single predecessor and there's no current insertion
// point to fall through from, then we can weld the epilog to that
// predecessor BB.
bool needsArg = false;
if (!epilogBB->bbarg_empty()) {
assert(epilogBB->bbarg_size() == 1 && "epilog should take 0 or 1 args");
needsArg = true;
}
// Steal the branch argument as the return value if present.
SILBasicBlock *pred = *epilogBB->pred_begin();
BranchInst *predBranch = cast<BranchInst>(pred->getTerminator());
assert(predBranch->getArgs().size() == (needsArg ? 1 : 0) &&
"epilog predecessor arguments does not match block params");
if (needsArg) {
returnValue = predBranch->getArgs()[0];
// RAUW the old BB argument (if any) with the new value.
SILValue(*epilogBB->bbarg_begin(),0).replaceAllUsesWith(returnValue);
}
// If we are optimizing, we should use the return location from the single,
// previously processed, return statement if any.
if (predBranch->getLoc().is<ReturnLocation>()) {
returnLoc = predBranch->getLoc();
} else {
returnLoc = ImplicitReturnFromTopLevel;
}
// Kill the branch to the now-dead epilog BB.
pred->erase(predBranch);
// Move any instructions from the EpilogBB to the end of the 'pred' block.
pred->spliceAtEnd(epilogBB);
// Finally we can erase the epilog BB.
eraseBasicBlock(epilogBB);
// Emit the epilog into its former predecessor.
B.setInsertionPoint(pred);
} else {
// Move the epilog block to the end of the ordinary section.
auto endOfOrdinarySection =
(StartOfPostmatter ? SILFunction::iterator(StartOfPostmatter) : F.end());
B.moveBlockTo(epilogBB, endOfOrdinarySection);
// Emit the epilog into the epilog bb. Its argument is the return value.
if (!epilogBB->bbarg_empty()) {
assert(epilogBB->bbarg_size() == 1 && "epilog should take 0 or 1 args");
returnValue = epilogBB->bbarg_begin()[0];
}
// If we are falling through from the current block, the return is implicit.
B.emitBlock(epilogBB, ImplicitReturnFromTopLevel);
}
// Emit top-level cleanups into the epilog block.
assert(!Cleanups.hasAnyActiveCleanups(getCleanupsDepth(),
ReturnDest.getDepth()) &&
"emitting epilog in wrong scope");
auto cleanupLoc = CleanupLocation::get(TopLevel);
Cleanups.emitCleanupsForReturn(cleanupLoc);
// If the return location is known to be that of an already
// processed return, use it. (This will get triggered when the
// epilog logic is simplified.)
//
// Otherwise make the ret instruction part of the cleanups.
if (!returnLoc) returnLoc = cleanupLoc;
return { returnValue, *returnLoc };
}
static Optional<SILLocation>
prepareForEpilogBlockEmission(SILGenFunction &SGF, SILLocation topLevel,
SILBasicBlock *epilogBB,
SmallVectorImpl<SILValue> &directResults) {
SILLocation implicitReturnFromTopLevel =
ImplicitReturnLocation::getImplicitReturnLoc(topLevel);
// If the current BB we are inserting into isn't terminated, and we require a
// return, then we
// are not allowed to fall off the end of the function and can't reach here.
if (SGF.NeedsReturn && SGF.B.hasValidInsertionPoint())
SGF.B.createUnreachable(implicitReturnFromTopLevel);
if (epilogBB->pred_empty()) {
// If the epilog was not branched to at all, kill the BB and
// just emit the epilog into the current BB.
while (!epilogBB->empty())
epilogBB->back().eraseFromParent();
SGF.eraseBasicBlock(epilogBB);
// If the current bb is terminated then the epilog is just unreachable.
if (!SGF.B.hasValidInsertionPoint())
return None;
// We emit the epilog at the current insertion point.
return implicitReturnFromTopLevel;
}
if (std::next(epilogBB->pred_begin()) == epilogBB->pred_end() &&
!SGF.B.hasValidInsertionPoint()) {
// If the epilog has a single predecessor and there's no current insertion
// point to fall through from, then we can weld the epilog to that
// predecessor BB.
// Steal the branch argument as the return value if present.
SILBasicBlock *pred = *epilogBB->pred_begin();
BranchInst *predBranch = cast<BranchInst>(pred->getTerminator());
assert(predBranch->getArgs().size() == epilogBB->args_size() &&
"epilog predecessor arguments does not match block params");
for (auto index : indices(predBranch->getArgs())) {
SILValue result = predBranch->getArgs()[index];
directResults.push_back(result);
epilogBB->getArgument(index)->replaceAllUsesWith(result);
}
Optional<SILLocation> returnLoc;
// If we are optimizing, we should use the return location from the single,
// previously processed, return statement if any.
if (predBranch->getLoc().is<ReturnLocation>()) {
returnLoc = predBranch->getLoc();
} else {
returnLoc = implicitReturnFromTopLevel;
}
// Kill the branch to the now-dead epilog BB.
pred->erase(predBranch);
// Move any instructions from the EpilogBB to the end of the 'pred' block.
pred->spliceAtEnd(epilogBB);
// Finally we can erase the epilog BB.
SGF.eraseBasicBlock(epilogBB);
// Emit the epilog into its former predecessor.
SGF.B.setInsertionPoint(pred);
return returnLoc;
}
// Move the epilog block to the end of the ordinary section.
auto endOfOrdinarySection = SGF.StartOfPostmatter;
SGF.B.moveBlockTo(epilogBB, endOfOrdinarySection);
// Emit the epilog into the epilog bb. Its arguments are the
// direct results.
directResults.append(epilogBB->args_begin(), epilogBB->args_end());
// If we are falling through from the current block, the return is implicit.
SGF.B.emitBlock(epilogBB, implicitReturnFromTopLevel);
// If the return location is known to be that of an already
// processed return, use it. (This will get triggered when the
// epilog logic is simplified.)
//
// Otherwise make the ret instruction part of the cleanups.
auto cleanupLoc = CleanupLocation::get(topLevel);
return cleanupLoc;
}
