break-crit-edges incorrectly updates idoms for unreachable code #1482
Description
| Bugzilla Link | 1110 |
| Resolution | FIXED |
| Resolved on | Nov 07, 2018 00:17 |
| Version | 1.0 |
| OS | All |
| Attachments | testcase |
| CC | @asl |
Extended Description
Steps to reproduce:
$ llvm/Debug/bin/opt -etforest -break-crit-edges -domtree x.bc -disable-output
Segmentation fault
The backtrace shows an infinite loop
#123147 0x085b20b7 in llvm::DominatorTree::getNodeForBlock (this=0x87191f8,
BB=0x0) at Dominators.cpp:380
but before that, it seems that llvm::DominatorTree::calculate's "ImmDom", which
is gets from ImmediateDominator is out of date:
#174577 0x085b225f in llvm::DominatorTree::calculate (this=0x87191f8,
ID=@0x871a1a8) at Dominators.cpp:399
399 Node *IDomNode = getNodeForBlock(ImmDom);
(gdb) p ImmDom
$2 = (class llvm::BasicBlock *) 0x8719838
(gdb) p ImmDom->getName()
Cannot access memory at address 0xff75effc
(gdb) down
#174576 0x085b20b7 in llvm::DominatorTree::getNodeForBlock (this=0x87191f8,
BB=0x8719838) at Dominators.cpp:380
380 Node *IDomNode = getNodeForBlock(IDom);
(gdb) p IDom
$3 = (class llvm::BasicBlock *) 0x0
and that's the start of the infinite loop.