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Prune the unwind_to labels on BBs that don't need them. Another step in the

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removal of invoke, PR1269.

llvm-svn: 48084
This commit is contained in:
Nick Lewycky 2008-03-09 04:55:16 +00:00
parent b741ebba29
commit 980738baf2
2 changed files with 31 additions and 3 deletions
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19
lib/Transforms/IPO/PruneEH.cpp
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@ -32,6 +32,7 @@ using namespace llvm;
STATISTIC(NumRemoved, "Number of invokes removed");
STATISTIC(NumUnreach, "Number of noreturn calls optimized");
STATISTIC(NumBBUnwind, "Number of unwind_to removed from blocks");
namespace {
struct VISIBILITY_HIDDEN PruneEH : public CallGraphSCCPass {
@ -153,6 +154,8 @@ bool PruneEH::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
bool PruneEH::SimplifyFunction(Function *F) {
bool MadeChange = false;
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
bool couldUnwind = false;
if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
if (II->doesNotThrow()) {
SmallVector<Value*, 8> Args(II->op_begin()+3, II->op_end());
@ -182,10 +185,11 @@ bool PruneEH::SimplifyFunction(Function *F) {
++NumRemoved;
MadeChange = true;
}
} else
couldUnwind = true;
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; )
if (CallInst *CI = dyn_cast<CallInst>(I++))
if (CallInst *CI = dyn_cast<CallInst>(I++)) {
if (CI->doesNotReturn() && !isa<UnreachableInst>(I)) {
// This call calls a function that cannot return. Insert an
// unreachable instruction after it and simplify the code. Do this
@ -201,8 +205,17 @@ bool PruneEH::SimplifyFunction(Function *F) {
MadeChange = true;
++NumUnreach;
break;
}
} else if (!CI->doesNotThrow())
couldUnwind = true;
}
// Strip 'unwindTo' off of BBs that have no calls/invokes without nounwind.
if (!couldUnwind && BB->getUnwindDest()) {
MadeChange = true;
++NumBBUnwind;
BB->getUnwindDest()->removePredecessor(BB, false, true);
BB->setUnwindDest(NULL);
}
}
return MadeChange;
}

15
test/Transforms/PruneEH/unwindto.ll Normal file
View File

@ -0,0 +1,15 @@
; RUN: llvm-as < %s | opt -prune-eh | llvm-dis | not grep unwind_to
define i8 @test7(i1 %b) {
entry: unwind_to %cleanup
br i1 %b, label %cond_true, label %cond_false
cond_true: unwind_to %cleanup
br label %cleanup
cond_false: unwind_to %cleanup
br label %cleanup
cleanup:
%x = phi i8 [0, %entry], [1, %cond_true], [1, %cond_true],
[2, %cond_false], [2, %cond_false]
ret i8 %x
}