averello/swift-mirror
1
0
Fork 0
mirror of https://github.com/apple/swift.git synced 2025-12-21 12:14:44 +01:00
Code Issues Packages Projects Releases Wiki Activity

SimplifyCFG: fix a crash caused by an unreachable CFG cycles with block arguments.

Browse Source 
When SimplifyCFG (temporarily) produces an unreachable CFG cycle, some other transformations in SimplifyCFG didn't deal with this situation correctly.

Unfortunately I couldn't create a SIL test case for this bug, so I just added a swift test case.

https://bugs.swift.org/browse/SR-13650
rdar://problem/69942431
This commit is contained in:
Erik Eckstein
2020-10-15 15:04:16 +02:00
parent aa3e5904f8
commit 6c85f267bf
3 changed files with 46 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

32
lib/SILOptimizer/Transforms/SimplifyCFG.cpp
View File

@@ -1248,21 +1248,8 @@ bool SimplifyCFG::simplifyBranchBlock(BranchInst *BI) {
LLVM_DEBUG(llvm::dbgs() << "merge bb" << BB->getDebugID() << " with bb"
<< DestBB->getDebugID() << '\n');
// If there are any BB arguments in the destination, replace them with the
// branch operands, since they must dominate the dest block.
for (unsigned i = 0, e = BI->getArgs().size(); i != e; ++i) {
if (DestBB->getArgument(i) != BI->getArg(i)) {
SILValue Val = BI->getArg(i);
DestBB->getArgument(i)->replaceAllUsesWith(Val);
if (!isVeryLargeFunction) {
if (auto *I = dyn_cast<SingleValueInstruction>(Val)) {
// Replacing operands may trigger constant folding which then could
// trigger other simplify-CFG optimizations.
ConstFolder.addToWorklist(I);
ConstFolder.processWorkList();
}
}
} else {
if (DestBB->getArgument(i) == BI->getArg(i)) {
// We must be processing an unreachable part of the cfg with a cycle.
// bb1(arg1): // preds: bb3
// br bb2
@@ -1273,6 +1260,23 @@ bool SimplifyCFG::simplifyBranchBlock(BranchInst *BI) {
// bb3: // preds: bb2
// br bb1(arg1)
assert(!isReachable(BB) && "Should only occur in unreachable block");
return Simplified;
}
}
// If there are any BB arguments in the destination, replace them with the
// branch operands, since they must dominate the dest block.
for (unsigned i = 0, e = BI->getArgs().size(); i != e; ++i) {
assert(DestBB->getArgument(i) != BI->getArg(i));
SILValue Val = BI->getArg(i);
DestBB->getArgument(i)->replaceAllUsesWith(Val);
if (!isVeryLargeFunction) {
if (auto *I = dyn_cast<SingleValueInstruction>(Val)) {
// Replacing operands may trigger constant folding which then could
// trigger other simplify-CFG optimizations.
ConstFolder.addToWorklist(I);
ConstFolder.processWorkList();
}
}
}