2002-04-08 04:49:59 +08:00
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//===- UnifyFunctionExitNodes.cpp - Make all functions have a single exit -===//
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2005-04-22 07:48:37 +08:00
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//
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2003-10-21 03:43:21 +08:00
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// The LLVM Compiler Infrastructure
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//
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2007-12-30 04:36:04 +08:00
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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2005-04-22 07:48:37 +08:00
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//
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2003-10-21 03:43:21 +08:00
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//===----------------------------------------------------------------------===//
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2001-07-07 00:58:36 +08:00
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//
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2002-05-08 02:51:25 +08:00
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// This pass is used to ensure that functions have at most one return
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// instruction in them. Additionally, it keeps track of which node is the new
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// exit node of the CFG. If there are no exit nodes in the CFG, the getExitNode
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// method will return a null pointer.
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2001-07-07 00:58:36 +08:00
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//
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//===----------------------------------------------------------------------===//
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2002-05-08 03:18:48 +08:00
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#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
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2003-04-01 01:30:25 +08:00
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#include "llvm/Transforms/Scalar.h"
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2001-07-07 00:58:36 +08:00
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#include "llvm/BasicBlock.h"
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2002-04-08 04:49:59 +08:00
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#include "llvm/Function.h"
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2004-07-29 20:17:34 +08:00
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#include "llvm/Instructions.h"
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2001-07-07 00:58:36 +08:00
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#include "llvm/Type.h"
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2008-03-11 02:11:41 +08:00
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#include "llvm/ADT/StringExtras.h"
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2003-11-22 00:52:05 +08:00
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using namespace llvm;
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2003-11-12 06:41:34 +08:00
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2007-05-03 09:11:54 +08:00
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char UnifyFunctionExitNodes::ID = 0;
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2006-08-28 06:42:52 +08:00
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static RegisterPass<UnifyFunctionExitNodes>
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2002-07-24 02:06:35 +08:00
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X("mergereturn", "Unify function exit nodes");
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2002-01-31 08:42:27 +08:00
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2003-11-22 00:52:05 +08:00
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Pass *llvm::createUnifyFunctionExitNodesPass() {
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2003-09-11 04:34:51 +08:00
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return new UnifyFunctionExitNodes();
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}
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2003-04-01 01:30:25 +08:00
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void UnifyFunctionExitNodes::getAnalysisUsage(AnalysisUsage &AU) const{
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// We preserve the non-critical-edgeness property
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AU.addPreservedID(BreakCriticalEdgesID);
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2006-05-09 12:13:41 +08:00
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// This is a cluster of orthogonal Transforms
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AU.addPreservedID(PromoteMemoryToRegisterID);
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AU.addPreservedID(LowerSwitchID);
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2003-04-01 01:30:25 +08:00
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}
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2001-07-07 00:58:36 +08:00
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// UnifyAllExitNodes - Unify all exit nodes of the CFG by creating a new
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// BasicBlock, and converting all returns to unconditional branches to this
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// new basic block. The singular exit node is returned.
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//
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2002-04-08 04:49:59 +08:00
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// If there are no return stmts in the Function, a null pointer is returned.
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2001-07-07 00:58:36 +08:00
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//
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2002-06-26 00:12:52 +08:00
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bool UnifyFunctionExitNodes::runOnFunction(Function &F) {
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2002-04-08 04:49:59 +08:00
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// Loop over all of the blocks in a function, tracking all of the blocks that
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2001-07-07 00:58:36 +08:00
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// return.
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//
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2003-05-23 06:00:07 +08:00
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std::vector<BasicBlock*> ReturningBlocks;
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2003-09-11 04:34:51 +08:00
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std::vector<BasicBlock*> UnwindingBlocks;
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2004-10-17 02:21:33 +08:00
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std::vector<BasicBlock*> UnreachableBlocks;
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2002-06-26 00:12:52 +08:00
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for(Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
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if (isa<ReturnInst>(I->getTerminator()))
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ReturningBlocks.push_back(I);
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2003-09-11 04:34:51 +08:00
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else if (isa<UnwindInst>(I->getTerminator()))
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UnwindingBlocks.push_back(I);
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2004-10-17 02:21:33 +08:00
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else if (isa<UnreachableInst>(I->getTerminator()))
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UnreachableBlocks.push_back(I);
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2003-09-11 04:34:51 +08:00
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2004-10-17 02:21:33 +08:00
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// Handle unwinding blocks first.
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2003-09-11 04:34:51 +08:00
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if (UnwindingBlocks.empty()) {
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UnwindBlock = 0;
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} else if (UnwindingBlocks.size() == 1) {
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UnwindBlock = UnwindingBlocks.front();
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} else {
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2009-08-14 05:58:54 +08:00
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UnwindBlock = BasicBlock::Create(F.getContext(), "UnifiedUnwindBlock", &F);
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new UnwindInst(F.getContext(), UnwindBlock);
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2001-07-07 00:58:36 +08:00
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2005-04-22 07:48:37 +08:00
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for (std::vector<BasicBlock*>::iterator I = UnwindingBlocks.begin(),
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2003-09-11 04:34:51 +08:00
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E = UnwindingBlocks.end(); I != E; ++I) {
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BasicBlock *BB = *I;
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2004-10-17 02:21:33 +08:00
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BB->getInstList().pop_back(); // Remove the unwind insn
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2008-04-07 04:25:17 +08:00
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BranchInst::Create(UnwindBlock, BB);
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2003-09-11 04:34:51 +08:00
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}
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}
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2004-10-17 02:21:33 +08:00
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// Then unreachable blocks.
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if (UnreachableBlocks.empty()) {
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UnreachableBlock = 0;
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} else if (UnreachableBlocks.size() == 1) {
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UnreachableBlock = UnreachableBlocks.front();
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} else {
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2009-08-14 05:58:54 +08:00
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UnreachableBlock = BasicBlock::Create(F.getContext(),
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"UnifiedUnreachableBlock", &F);
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new UnreachableInst(F.getContext(), UnreachableBlock);
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2004-10-17 02:21:33 +08:00
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2005-04-22 07:48:37 +08:00
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for (std::vector<BasicBlock*>::iterator I = UnreachableBlocks.begin(),
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2004-10-17 02:21:33 +08:00
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E = UnreachableBlocks.end(); I != E; ++I) {
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BasicBlock *BB = *I;
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BB->getInstList().pop_back(); // Remove the unreachable inst.
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2008-04-07 04:25:17 +08:00
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BranchInst::Create(UnreachableBlock, BB);
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2004-10-17 02:21:33 +08:00
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}
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}
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// Now handle return blocks.
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2002-02-01 12:53:48 +08:00
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if (ReturningBlocks.empty()) {
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2003-09-11 04:34:51 +08:00
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ReturnBlock = 0;
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2002-05-08 02:51:25 +08:00
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return false; // No blocks return
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2002-01-31 09:12:06 +08:00
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} else if (ReturningBlocks.size() == 1) {
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2003-09-11 04:34:51 +08:00
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ReturnBlock = ReturningBlocks.front(); // Already has a single return block
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2002-01-31 09:12:06 +08:00
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return false;
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}
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2001-07-07 00:58:36 +08:00
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2002-04-08 04:49:59 +08:00
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// Otherwise, we need to insert a new basic block into the function, add a PHI
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2008-03-06 05:50:24 +08:00
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// nodes (if the function returns values), and convert all of the return
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2001-07-07 00:58:36 +08:00
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// instructions into unconditional branches.
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//
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2009-08-14 05:58:54 +08:00
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BasicBlock *NewRetBlock = BasicBlock::Create(F.getContext(),
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"UnifiedReturnBlock", &F);
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2001-07-07 00:58:36 +08:00
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2008-07-23 08:34:11 +08:00
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PHINode *PN = 0;
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2009-08-14 05:58:54 +08:00
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if (F.getReturnType() == Type::getVoidTy(F.getContext())) {
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ReturnInst::Create(F.getContext(), NULL, NewRetBlock);
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2008-07-23 08:34:11 +08:00
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} else {
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2002-04-08 04:49:59 +08:00
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// If the function doesn't return void... add a PHI node to the block...
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2008-07-23 08:34:11 +08:00
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PN = PHINode::Create(F.getReturnType(), "UnifiedRetVal");
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2002-09-11 07:31:28 +08:00
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NewRetBlock->getInstList().push_back(PN);
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2009-08-14 05:58:54 +08:00
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ReturnInst::Create(F.getContext(), PN, NewRetBlock);
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2001-07-07 00:58:36 +08:00
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}
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// Loop over all of the blocks, replacing the return instruction with an
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// unconditional branch.
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//
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2005-04-22 07:48:37 +08:00
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for (std::vector<BasicBlock*>::iterator I = ReturningBlocks.begin(),
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2003-05-23 06:00:07 +08:00
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E = ReturningBlocks.end(); I != E; ++I) {
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2003-04-01 01:30:25 +08:00
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BasicBlock *BB = *I;
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// Add an incoming element to the PHI node for every return instruction that
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// is merging into this new block...
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2008-07-23 08:34:11 +08:00
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if (PN)
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PN->addIncoming(BB->getTerminator()->getOperand(0), BB);
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2003-04-01 01:30:25 +08:00
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BB->getInstList().pop_back(); // Remove the return insn
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2008-04-07 04:25:17 +08:00
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BranchInst::Create(NewRetBlock, BB);
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2001-07-07 00:58:36 +08:00
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}
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2003-09-11 04:34:51 +08:00
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ReturnBlock = NewRetBlock;
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2002-01-31 09:12:06 +08:00
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return true;
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2001-07-07 00:58:36 +08:00
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}
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