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Implement PR1796 and Transforms/SimplifyCFG/noreturn-call.ll
by inserting unreachable after no-return calls. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44099 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -24,6 +24,7 @@
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#include "llvm/Constants.h"
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#include "llvm/Instructions.h"
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#include "llvm/Module.h"
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#include "llvm/ParameterAttributes.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Pass.h"
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@ -50,6 +51,46 @@ FunctionPass *llvm::createCFGSimplificationPass() {
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return new CFGSimplifyPass();
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}
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/// ChangeToUnreachable - Insert an unreachable instruction before the specified
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/// instruction, making it and the rest of the code in the block dead.
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static void ChangeToUnreachable(Instruction *I) {
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BasicBlock *BB = I->getParent();
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// Loop over all of the successors, removing BB's entry from any PHI
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// nodes.
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for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
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(*SI)->removePredecessor(BB);
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new UnreachableInst(I);
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// All instructions after this are dead.
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BasicBlock::iterator BBI = I, BBE = BB->end();
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while (BBI != BBE) {
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if (!BBI->use_empty())
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BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
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BB->getInstList().erase(BBI++);
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}
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}
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/// IsNoReturn - Return true if the specified call is to a no-return function.
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static bool IsNoReturn(const CallInst *CI) {
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if (const ParamAttrsList *Attrs = CI->getParamAttrs())
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if (Attrs->paramHasAttr(0, ParamAttr::NoReturn))
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return true;
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if (const Function *Callee = CI->getCalledFunction()) {
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if (const ParamAttrsList *Attrs = Callee->getParamAttrs())
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if (Attrs->paramHasAttr(0, ParamAttr::NoReturn))
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return true;
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const FunctionType *FT = Callee->getFunctionType();
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if (const ParamAttrsList *Attrs = FT->getParamAttrs())
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if (Attrs->paramHasAttr(0, ParamAttr::NoReturn))
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return true;
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}
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return false;
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}
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static bool MarkAliveBlocks(BasicBlock *BB,
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SmallPtrSet<BasicBlock*, 128> &Reachable) {
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@ -66,26 +107,29 @@ static bool MarkAliveBlocks(BasicBlock *BB,
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// Do a quick scan of the basic block, turning any obviously unreachable
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// instructions into LLVM unreachable insts. The instruction combining pass
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// canonnicalizes unreachable insts into stores to null or undef.
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for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ++BBI)
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if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
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if (isa<ConstantPointerNull>(SI->getOperand(1)) ||
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isa<UndefValue>(SI->getOperand(1))) {
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// Loop over all of the successors, removing BB's entry from any PHI
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// nodes.
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for (succ_iterator I = succ_begin(BB), SE = succ_end(BB); I != SE;++I)
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(*I)->removePredecessor(BB);
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new UnreachableInst(SI);
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// All instructions after this are dead.
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while (BBI != E) {
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if (!BBI->use_empty())
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BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
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BB->getInstList().erase(BBI++);
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for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
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if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
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if (IsNoReturn(CI)) {
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// If we found a call to a no-return function, insert an unreachable
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// instruction after it. Make sure there isn't *already* one there
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// though.
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++BBI;
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if (!isa<UnreachableInst>(BBI)) {
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ChangeToUnreachable(BBI);
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Changed = true;
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}
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break;
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}
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}
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if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
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if (isa<ConstantPointerNull>(SI->getOperand(1)) ||
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isa<UndefValue>(SI->getOperand(1))) {
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ChangeToUnreachable(SI);
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Changed = true;
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break;
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}
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}
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Changed |= ConstantFoldTerminator(BB);
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for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
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11
test/Transforms/SimplifyCFG/noreturn-call.ll
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11
test/Transforms/SimplifyCFG/noreturn-call.ll
Normal file
@ -0,0 +1,11 @@
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; RUN: llvm-as < %s | opt -simplifycfg | llvm-dis | grep unreachable
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; PR1796
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declare void @Finisher(i32) noreturn
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define void @YYY(i32) {
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tail call void @Finisher(i32 %0) noreturn
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tail call void @Finisher(i32 %0) noreturn
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ret void
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}
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