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Do a simple instcombine xforms to delete llvm.stackrestore cases.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@25294 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -4671,6 +4671,39 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
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SPI->replaceAllUsesWith(PrevSPI);
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return EraseInstFromFunction(CI);
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}
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} else {
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switch (II->getIntrinsicID()) {
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default: break;
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case Intrinsic::stackrestore: {
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// If the save is right next to the restore, remove the restore. This can
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// happen when variable allocas are DCE'd.
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if (IntrinsicInst *SS = dyn_cast<IntrinsicInst>(II->getOperand(1))) {
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if (SS->getIntrinsicID() == Intrinsic::stacksave) {
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BasicBlock::iterator BI = SS;
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if (&*++BI == II)
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return EraseInstFromFunction(CI);
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}
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}
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// If the stack restore is in a return/unwind block and if there are no
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// allocas or calls between the restore and the return, nuke the restore.
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TerminatorInst *TI = II->getParent()->getTerminator();
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if (isa<ReturnInst>(TI) || isa<UnwindInst>(TI)) {
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BasicBlock::iterator BI = II;
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bool CannotRemove = false;
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for (++BI; &*BI != TI; ++BI) {
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if (isa<AllocaInst>(BI) ||
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(isa<CallInst>(BI) && !isa<IntrinsicInst>(BI))) {
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CannotRemove = true;
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break;
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}
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}
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if (!CannotRemove)
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return EraseInstFromFunction(CI);
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}
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break;
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}
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}
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}
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return visitCallSite(II);
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