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Fix PR8445: a block with no predecessors may be the entry block, in which case

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it isn't unreachable and should not be zapped.  The check for the entry block
was missing in one case: a block containing a unwind instruction.  While there,
do some small cleanups: "M" is not a great name for a Function* (it would be
more appropriate for a Module*), change it to "Fn"; use Fn in more places.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117224 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2010-10-24 12:23:30 +00:00
parent c052a8c772
commit 5f28475b30
2 changed files with 16 additions and 12 deletions
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22
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -1720,15 +1720,14 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) {
bool SimplifyCFGOpt::run(BasicBlock *BB) { bool SimplifyCFGOpt::run(BasicBlock *BB) {
bool Changed = false; bool Changed = false;
Function *M = BB->getParent(); Function *Fn = BB->getParent();
assert(BB && BB->getParent() && "Block not embedded in function!"); assert(BB && Fn && "Block not embedded in function!");
assert(BB->getTerminator() && "Degenerate basic block encountered!"); assert(BB->getTerminator() && "Degenerate basic block encountered!");
// Remove basic blocks that have no predecessors (except the entry block)... // Remove basic blocks that have no predecessors (except the entry block)...
// or that just have themself as a predecessor. These are unreachable. // or that just have themself as a predecessor. These are unreachable.
if ((pred_begin(BB) == pred_end(BB) && if ((pred_begin(BB) == pred_end(BB) && BB != &Fn->getEntryBlock()) ||
&BB->getParent()->getEntryBlock() != BB) ||
BB->getSinglePredecessor() == BB) { BB->getSinglePredecessor() == BB) {
DEBUG(dbgs() << "Removing BB: \n" << *BB); DEBUG(dbgs() << "Removing BB: \n" << *BB);
DeleteDeadBlock(BB); DeleteDeadBlock(BB);
@ -1798,7 +1797,7 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
// If we eliminated all predecessors of the block, delete the block now. // If we eliminated all predecessors of the block, delete the block now.
if (pred_begin(BB) == pred_end(BB)) if (pred_begin(BB) == pred_end(BB))
// We know there are no successors, so just nuke the block. // We know there are no successors, so just nuke the block.
M->getBasicBlockList().erase(BB); Fn->getBasicBlockList().erase(BB);
return true; return true;
} }
@ -1847,10 +1846,10 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
Preds.pop_back(); Preds.pop_back();
} }
// If this block is now dead, remove it. // If this block is now dead (and isn't the entry block), remove it.
if (pred_begin(BB) == pred_end(BB)) { if (pred_begin(BB) == pred_end(BB) && BB != &Fn->getEntryBlock()) {
// We know there are no successors, so just nuke the block. // We know there are no successors, so just nuke the block.
M->getBasicBlockList().erase(BB); Fn->getBasicBlockList().erase(BB);
return true; return true;
} }
@ -1880,7 +1879,7 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
while (isa<DbgInfoIntrinsic>(BBI)) while (isa<DbgInfoIntrinsic>(BBI))
++BBI; ++BBI;
if (BBI->isTerminator()) // Terminator is the only non-phi instruction! if (BBI->isTerminator()) // Terminator is the only non-phi instruction!
if (BB != &BB->getParent()->getEntryBlock()) if (BB != &Fn->getEntryBlock())
if (TryToSimplifyUncondBranchFromEmptyBlock(BB)) if (TryToSimplifyUncondBranchFromEmptyBlock(BB))
return true; return true;
@ -2050,10 +2049,9 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
} }
// If this block is now dead, remove it. // If this block is now dead, remove it.
if (pred_begin(BB) == pred_end(BB) && if (pred_begin(BB) == pred_end(BB) && BB != &Fn->getEntryBlock()) {
BB != &BB->getParent()->getEntryBlock()) {
// We know there are no successors, so just nuke the block. // We know there are no successors, so just nuke the block.
M->getBasicBlockList().erase(BB); Fn->getBasicBlockList().erase(BB);
return true; return true;
} }
} }

6
test/Transforms/SimplifyCFG/2010-10-24-OnlyUnwindInEntry.ll Normal file
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@ -0,0 +1,6 @@
; RUN: opt %s -simplifycfg -disable-output
; PR8445
define void @test() {
unwind
}