BasicBlock.cpp revision 1d0be15f89cb5056e20e2d24faa8d6afb1573bca
1d1e693f2a3883dacf213aa2b477540c57b53b714Chris Lattner//===-- BasicBlock.cpp - Implement BasicBlock related methods -------------===// 2fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman// 3b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// The LLVM Compiler Infrastructure 4b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// 54ee451de366474b9c228b4e5fa573795a715216dChris Lattner// This file is distributed under the University of Illinois Open Source 64ee451de366474b9c228b4e5fa573795a715216dChris Lattner// License. See LICENSE.TXT for details. 7fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman// 8b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell//===----------------------------------------------------------------------===// 9009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner// 10b7653df0853f06112b741be09f1b7ae5a6aa6fdeChris Lattner// This file implements the BasicBlock class for the VMCore library. 11009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner// 12009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner//===----------------------------------------------------------------------===// 13009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner 140a4fd1ab7e7c83b3ecf03cbd6b35d2b164995267Gabor Greif#include "llvm/BasicBlock.h" 153464547968b58dda0acbf6e0e192f03f66652848Chris Lattner#include "llvm/Constants.h" 1644336292fcd9f3f99cbfc2c3366bea0cf95bb675Misha Brukman#include "llvm/Instructions.h" 17f81b57694b3c34a79b1464ffd21e6768c8d22662Owen Anderson#include "llvm/LLVMContext.h" 18009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner#include "llvm/Type.h" 19fed90b6d097d50881afb45e4d79f430db66dd741Dan Gohman#include "llvm/ADT/STLExtras.h" 20455889aa79e3463a4b0f2161e3d9d72a683268b6Chris Lattner#include "llvm/Support/CFG.h" 21551ccae044b0ff658fe629dd67edd5ffe75d10e8Reid Spencer#include "llvm/Support/LeakDetector.h" 227e70829632f82de15db187845666aaca6e04b792Chris Lattner#include "SymbolTableListTraitsImpl.h" 237e70829632f82de15db187845666aaca6e04b792Chris Lattner#include <algorithm> 24108e4ab159b59a616b0868e396dc7ddc1fb48616Chris Lattnerusing namespace llvm; 25108e4ab159b59a616b0868e396dc7ddc1fb48616Chris Lattner 260dd2a6a89f49438b239638ab147ac5746d6c32c3Gabor GreifValueSymbolTable *BasicBlock::getValueSymbolTable() { 270dd2a6a89f49438b239638ab147ac5746d6c32c3Gabor Greif if (Function *F = getParent()) 280dd2a6a89f49438b239638ab147ac5746d6c32c3Gabor Greif return &F->getValueSymbolTable(); 2917fcdd5e1b78b829068ca657c97357a39d6e768bChris Lattner return 0; 3017fcdd5e1b78b829068ca657c97357a39d6e768bChris Lattner} 3117fcdd5e1b78b829068ca657c97357a39d6e768bChris Lattner 32e922c0201916e0b980ab3cfe91e1413e68d55647Owen AndersonLLVMContext &BasicBlock::getContext() const { 33e922c0201916e0b980ab3cfe91e1413e68d55647Owen Anderson return getType()->getContext(); 340a205a459884ec745df1c529396dd921f029dafdOwen Anderson} 350a205a459884ec745df1c529396dd921f029dafdOwen Anderson 367e70829632f82de15db187845666aaca6e04b792Chris Lattner// Explicit instantiation of SymbolTableListTraits since some of the methods 377e70829632f82de15db187845666aaca6e04b792Chris Lattner// are not in the public header file... 3817fcdd5e1b78b829068ca657c97357a39d6e768bChris Lattnertemplate class SymbolTableListTraits<Instruction, BasicBlock>; 397e70829632f82de15db187845666aaca6e04b792Chris Lattner 40009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner 411d0be15f89cb5056e20e2d24faa8d6afb1573bcaOwen AndersonBasicBlock::BasicBlock(LLVMContext &C, const Twine &Name, Function *NewParent, 42280a6e607d8eb7401749a92db624a82de47da777Nick Lewycky BasicBlock *InsertBefore) 431d0be15f89cb5056e20e2d24faa8d6afb1573bcaOwen Anderson : Value(Type::getLabelTy(C), Value::BasicBlockVal), Parent(0) { 440a1a874d1f4659f02c0d4fdd6be69f1188bd0625Chris Lattner 450a1a874d1f4659f02c0d4fdd6be69f1188bd0625Chris Lattner // Make sure that we get added to a function 460a1a874d1f4659f02c0d4fdd6be69f1188bd0625Chris Lattner LeakDetector::addGarbageObject(this); 470a1a874d1f4659f02c0d4fdd6be69f1188bd0625Chris Lattner 480a1a874d1f4659f02c0d4fdd6be69f1188bd0625Chris Lattner if (InsertBefore) { 4917fcdd5e1b78b829068ca657c97357a39d6e768bChris Lattner assert(NewParent && 504f05611ed948ed1fb3e861d178aae18bd025ce1cChris Lattner "Cannot insert block before another block with no function!"); 5117fcdd5e1b78b829068ca657c97357a39d6e768bChris Lattner NewParent->getBasicBlockList().insert(InsertBefore, this); 5217fcdd5e1b78b829068ca657c97357a39d6e768bChris Lattner } else if (NewParent) { 5317fcdd5e1b78b829068ca657c97357a39d6e768bChris Lattner NewParent->getBasicBlockList().push_back(this); 540a1a874d1f4659f02c0d4fdd6be69f1188bd0625Chris Lattner } 55dec628eead87b20773c98a00830580df211acc98Chris Lattner 56dec628eead87b20773c98a00830580df211acc98Chris Lattner setName(Name); 570a1a874d1f4659f02c0d4fdd6be69f1188bd0625Chris Lattner} 580a1a874d1f4659f02c0d4fdd6be69f1188bd0625Chris Lattner 590a1a874d1f4659f02c0d4fdd6be69f1188bd0625Chris Lattner 60afba8fe662d65b25b4baf46bb26cc18e1f9cc0a5Gordon HenriksenBasicBlock::~BasicBlock() { 61afba8fe662d65b25b4baf46bb26cc18e1f9cc0a5Gordon Henriksen assert(getParent() == 0 && "BasicBlock still linked into the program!"); 62afba8fe662d65b25b4baf46bb26cc18e1f9cc0a5Gordon Henriksen dropAllReferences(); 63afba8fe662d65b25b4baf46bb26cc18e1f9cc0a5Gordon Henriksen InstList.clear(); 64009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner} 65009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner 66bded132d00ed626a6541b67ad101ef0fd47d3491Chris Lattnervoid BasicBlock::setParent(Function *parent) { 67d1e693f2a3883dacf213aa2b477540c57b53b714Chris Lattner if (getParent()) 68d1e693f2a3883dacf213aa2b477540c57b53b714Chris Lattner LeakDetector::addGarbageObject(this); 69d1e693f2a3883dacf213aa2b477540c57b53b714Chris Lattner 7017fcdd5e1b78b829068ca657c97357a39d6e768bChris Lattner // Set Parent=parent, updating instruction symtab entries as appropriate. 7117fcdd5e1b78b829068ca657c97357a39d6e768bChris Lattner InstList.setSymTabObject(&Parent, parent); 72d1e693f2a3883dacf213aa2b477540c57b53b714Chris Lattner 73d1e693f2a3883dacf213aa2b477540c57b53b714Chris Lattner if (getParent()) 74d1e693f2a3883dacf213aa2b477540c57b53b714Chris Lattner LeakDetector::removeGarbageObject(this); 75bded132d00ed626a6541b67ad101ef0fd47d3491Chris Lattner} 76bded132d00ed626a6541b67ad101ef0fd47d3491Chris Lattner 774b83380f330b1c77bb9b4ad8f63bdcf1a596afd6Chris Lattnervoid BasicBlock::removeFromParent() { 784b83380f330b1c77bb9b4ad8f63bdcf1a596afd6Chris Lattner getParent()->getBasicBlockList().remove(this); 794b83380f330b1c77bb9b4ad8f63bdcf1a596afd6Chris Lattner} 804b83380f330b1c77bb9b4ad8f63bdcf1a596afd6Chris Lattner 814b83380f330b1c77bb9b4ad8f63bdcf1a596afd6Chris Lattnervoid BasicBlock::eraseFromParent() { 824b83380f330b1c77bb9b4ad8f63bdcf1a596afd6Chris Lattner getParent()->getBasicBlockList().erase(this); 834b83380f330b1c77bb9b4ad8f63bdcf1a596afd6Chris Lattner} 844b83380f330b1c77bb9b4ad8f63bdcf1a596afd6Chris Lattner 85a71965b1adf6bfeddfd3b38fdf7df9b4412bc6c2Chris Lattner/// moveBefore - Unlink this basic block from its current function and 86a71965b1adf6bfeddfd3b38fdf7df9b4412bc6c2Chris Lattner/// insert it into the function that MovePos lives in, right before MovePos. 876a13aed525f586fc8f475ce17ce7f6cf77ddd2f4Chris Lattnervoid BasicBlock::moveBefore(BasicBlock *MovePos) { 886a13aed525f586fc8f475ce17ce7f6cf77ddd2f4Chris Lattner MovePos->getParent()->getBasicBlockList().splice(MovePos, 896a13aed525f586fc8f475ce17ce7f6cf77ddd2f4Chris Lattner getParent()->getBasicBlockList(), this); 906a13aed525f586fc8f475ce17ce7f6cf77ddd2f4Chris Lattner} 916a13aed525f586fc8f475ce17ce7f6cf77ddd2f4Chris Lattner 92a71965b1adf6bfeddfd3b38fdf7df9b4412bc6c2Chris Lattner/// moveAfter - Unlink this basic block from its current function and 93a71965b1adf6bfeddfd3b38fdf7df9b4412bc6c2Chris Lattner/// insert it into the function that MovePos lives in, right after MovePos. 94a71965b1adf6bfeddfd3b38fdf7df9b4412bc6c2Chris Lattnervoid BasicBlock::moveAfter(BasicBlock *MovePos) { 95a71965b1adf6bfeddfd3b38fdf7df9b4412bc6c2Chris Lattner Function::iterator I = MovePos; 96a71965b1adf6bfeddfd3b38fdf7df9b4412bc6c2Chris Lattner MovePos->getParent()->getBasicBlockList().splice(++I, 97a71965b1adf6bfeddfd3b38fdf7df9b4412bc6c2Chris Lattner getParent()->getBasicBlockList(), this); 98a71965b1adf6bfeddfd3b38fdf7df9b4412bc6c2Chris Lattner} 99a71965b1adf6bfeddfd3b38fdf7df9b4412bc6c2Chris Lattner 1004b83380f330b1c77bb9b4ad8f63bdcf1a596afd6Chris Lattner 101009505452b713ed2e3a8e99c5545a6e721c65495Chris LattnerTerminatorInst *BasicBlock::getTerminator() { 102009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner if (InstList.empty()) return 0; 1037e70829632f82de15db187845666aaca6e04b792Chris Lattner return dyn_cast<TerminatorInst>(&InstList.back()); 104009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner} 105009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner 10650cdabcfd52e88381ade61450d98a1c757195befDan Gohmanconst TerminatorInst *BasicBlock::getTerminator() const { 107009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner if (InstList.empty()) return 0; 1087e70829632f82de15db187845666aaca6e04b792Chris Lattner return dyn_cast<TerminatorInst>(&InstList.back()); 109009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner} 110009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner 11102dea8b39f3acad5de1df36273444d149145e7fcDan GohmanInstruction* BasicBlock::getFirstNonPHI() { 11202dea8b39f3acad5de1df36273444d149145e7fcDan Gohman BasicBlock::iterator i = begin(); 11302dea8b39f3acad5de1df36273444d149145e7fcDan Gohman // All valid basic blocks should have a terminator, 11402dea8b39f3acad5de1df36273444d149145e7fcDan Gohman // which is not a PHINode. If we have an invalid basic 11502dea8b39f3acad5de1df36273444d149145e7fcDan Gohman // block we'll get an assertion failure when dereferencing 11602dea8b39f3acad5de1df36273444d149145e7fcDan Gohman // a past-the-end iterator. 11702dea8b39f3acad5de1df36273444d149145e7fcDan Gohman while (isa<PHINode>(i)) ++i; 11802dea8b39f3acad5de1df36273444d149145e7fcDan Gohman return &*i; 119dd49dbfe44098eb53b1ac29f017e422147572bbbVladimir Prus} 120dd49dbfe44098eb53b1ac29f017e422147572bbbVladimir Prus 121009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattnervoid BasicBlock::dropAllReferences() { 1227e70829632f82de15db187845666aaca6e04b792Chris Lattner for(iterator I = begin(), E = end(); I != E; ++I) 1237e70829632f82de15db187845666aaca6e04b792Chris Lattner I->dropAllReferences(); 124009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner} 125009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner 126ad993cbb77b26b36cee938686b3377c0d92abd5eChris Lattner/// getSinglePredecessor - If this basic block has a single predecessor block, 127ad993cbb77b26b36cee938686b3377c0d92abd5eChris Lattner/// return the block, otherwise return a null pointer. 128ad993cbb77b26b36cee938686b3377c0d92abd5eChris LattnerBasicBlock *BasicBlock::getSinglePredecessor() { 129ad993cbb77b26b36cee938686b3377c0d92abd5eChris Lattner pred_iterator PI = pred_begin(this), E = pred_end(this); 130ad993cbb77b26b36cee938686b3377c0d92abd5eChris Lattner if (PI == E) return 0; // No preds. 131ad993cbb77b26b36cee938686b3377c0d92abd5eChris Lattner BasicBlock *ThePred = *PI; 132ad993cbb77b26b36cee938686b3377c0d92abd5eChris Lattner ++PI; 133ad993cbb77b26b36cee938686b3377c0d92abd5eChris Lattner return (PI == E) ? ThePred : 0 /*multiple preds*/; 134ad993cbb77b26b36cee938686b3377c0d92abd5eChris Lattner} 135ad993cbb77b26b36cee938686b3377c0d92abd5eChris Lattner 13687f1e7796d02ea991bdbf084f312879988732a26Torok Edwin/// getUniquePredecessor - If this basic block has a unique predecessor block, 13787f1e7796d02ea991bdbf084f312879988732a26Torok Edwin/// return the block, otherwise return a null pointer. 13887f1e7796d02ea991bdbf084f312879988732a26Torok Edwin/// Note that unique predecessor doesn't mean single edge, there can be 1399053a739e50cb6f6b68268cc7c6b95146e66d396Torok Edwin/// multiple edges from the unique predecessor to this block (for example 1409053a739e50cb6f6b68268cc7c6b95146e66d396Torok Edwin/// a switch statement with multiple cases having the same destination). 14187f1e7796d02ea991bdbf084f312879988732a26Torok EdwinBasicBlock *BasicBlock::getUniquePredecessor() { 14287f1e7796d02ea991bdbf084f312879988732a26Torok Edwin pred_iterator PI = pred_begin(this), E = pred_end(this); 14387f1e7796d02ea991bdbf084f312879988732a26Torok Edwin if (PI == E) return 0; // No preds. 14487f1e7796d02ea991bdbf084f312879988732a26Torok Edwin BasicBlock *PredBB = *PI; 14587f1e7796d02ea991bdbf084f312879988732a26Torok Edwin ++PI; 14687f1e7796d02ea991bdbf084f312879988732a26Torok Edwin for (;PI != E; ++PI) { 14787f1e7796d02ea991bdbf084f312879988732a26Torok Edwin if (*PI != PredBB) 14887f1e7796d02ea991bdbf084f312879988732a26Torok Edwin return 0; 1499053a739e50cb6f6b68268cc7c6b95146e66d396Torok Edwin // The same predecessor appears multiple times in the predecessor list. 1509053a739e50cb6f6b68268cc7c6b95146e66d396Torok Edwin // This is OK. 15187f1e7796d02ea991bdbf084f312879988732a26Torok Edwin } 15287f1e7796d02ea991bdbf084f312879988732a26Torok Edwin return PredBB; 15387f1e7796d02ea991bdbf084f312879988732a26Torok Edwin} 15487f1e7796d02ea991bdbf084f312879988732a26Torok Edwin 155566f600779d8c28a81bb08951ec1962fe34322abChris Lattner/// removePredecessor - This method is used to notify a BasicBlock that the 156566f600779d8c28a81bb08951ec1962fe34322abChris Lattner/// specified Predecessor of the block is no longer able to reach it. This is 157fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman/// actually not used to update the Predecessor list, but is actually used to 158566f600779d8c28a81bb08951ec1962fe34322abChris Lattner/// update the PHI nodes that reside in the block. Note that this should be 159566f600779d8c28a81bb08951ec1962fe34322abChris Lattner/// called while the predecessor still refers to this block. 160566f600779d8c28a81bb08951ec1962fe34322abChris Lattner/// 1613464547968b58dda0acbf6e0e192f03f66652848Chris Lattnervoid BasicBlock::removePredecessor(BasicBlock *Pred, 162280a6e607d8eb7401749a92db624a82de47da777Nick Lewycky bool DontDeleteUselessPHIs) { 1631f21ef1511ce003fc177121b980e783b83992f82Chris Lattner assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs. 16435f0aecdb012ba150953f6f3a98862be9c72d265Chris Lattner find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) && 1659d80930e950214d026afd3a3d18cda32629efdb9Jeff Cohen "removePredecessor: BB is not a predecessor!"); 16635f0aecdb012ba150953f6f3a98862be9c72d265Chris Lattner 167f23586c7efe615d061c00c24cf62f03f7962776fChris Lattner if (InstList.empty()) return; 168a9e7781b3b8e457946491529816feab73c66d774Chris Lattner PHINode *APN = dyn_cast<PHINode>(&front()); 169a9e7781b3b8e457946491529816feab73c66d774Chris Lattner if (!APN) return; // Quick exit. 170b47af25099cac5c59795d6f1eb3b7cf9f962b32fChris Lattner 171b47af25099cac5c59795d6f1eb3b7cf9f962b32fChris Lattner // If there are exactly two predecessors, then we want to nuke the PHI nodes 172a9e7781b3b8e457946491529816feab73c66d774Chris Lattner // altogether. However, we cannot do this, if this in this case: 17387a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner // 17487a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner // Loop: 17587a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner // %x = phi [X, Loop] 17687a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner // %x2 = add %x, 1 ;; This would become %x2 = add %x2, 1 17787a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner // br Loop ;; %x2 does not dominate all uses 17887a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner // 17987a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner // This is because the PHI node input is actually taken from the predecessor 180fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman // basic block. The only case this can happen is with a self loop, so we 18187a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner // check for this case explicitly now. 182fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman // 183a9e7781b3b8e457946491529816feab73c66d774Chris Lattner unsigned max_idx = APN->getNumIncomingValues(); 184b47af25099cac5c59795d6f1eb3b7cf9f962b32fChris Lattner assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!"); 18587a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner if (max_idx == 2) { 186a9e7781b3b8e457946491529816feab73c66d774Chris Lattner BasicBlock *Other = APN->getIncomingBlock(APN->getIncomingBlock(0) == Pred); 18787a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner 18887a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner // Disable PHI elimination! 18987a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner if (this == Other) max_idx = 3; 19087a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner } 19187a09b10f8e03182e9edcb6e9ee8386f4a5d8daeChris Lattner 1923464547968b58dda0acbf6e0e192f03f66652848Chris Lattner // <= Two predecessors BEFORE I remove one? 1933464547968b58dda0acbf6e0e192f03f66652848Chris Lattner if (max_idx <= 2 && !DontDeleteUselessPHIs) { 194b00c582b6d40e6b9ff2d1ed4f5eaf7930e792aceChris Lattner // Yup, loop through and nuke the PHI nodes 1957e70829632f82de15db187845666aaca6e04b792Chris Lattner while (PHINode *PN = dyn_cast<PHINode>(&front())) { 1963464547968b58dda0acbf6e0e192f03f66652848Chris Lattner // Remove the predecessor first. 197280a6e607d8eb7401749a92db624a82de47da777Nick Lewycky PN->removeIncomingValue(Pred, !DontDeleteUselessPHIs); 198b47af25099cac5c59795d6f1eb3b7cf9f962b32fChris Lattner 199b47af25099cac5c59795d6f1eb3b7cf9f962b32fChris Lattner // If the PHI _HAD_ two uses, replace PHI node with its now *single* value 200dee430d26e14a3d7c8d86688d49ac8b116aa044fChris Lattner if (max_idx == 2) { 20102a78cf7eacf97f2c9584e29d02f77612aead35fChris Lattner if (PN->getOperand(0) != PN) 20202a78cf7eacf97f2c9584e29d02f77612aead35fChris Lattner PN->replaceAllUsesWith(PN->getOperand(0)); 20302a78cf7eacf97f2c9584e29d02f77612aead35fChris Lattner else 20402a78cf7eacf97f2c9584e29d02f77612aead35fChris Lattner // We are left with an infinite loop with no entries: kill the PHI. 2059e9a0d5fc26878e51a58a8b57900fcbf952c2691Owen Anderson PN->replaceAllUsesWith(UndefValue::get(PN->getType())); 206dee430d26e14a3d7c8d86688d49ac8b116aa044fChris Lattner getInstList().pop_front(); // Remove the PHI node 207dee430d26e14a3d7c8d86688d49ac8b116aa044fChris Lattner } 208dee430d26e14a3d7c8d86688d49ac8b116aa044fChris Lattner 209dee430d26e14a3d7c8d86688d49ac8b116aa044fChris Lattner // If the PHI node already only had one entry, it got deleted by 210dee430d26e14a3d7c8d86688d49ac8b116aa044fChris Lattner // removeIncomingValue. 211b47af25099cac5c59795d6f1eb3b7cf9f962b32fChris Lattner } 212b47af25099cac5c59795d6f1eb3b7cf9f962b32fChris Lattner } else { 213b47af25099cac5c59795d6f1eb3b7cf9f962b32fChris Lattner // Okay, now we know that we need to remove predecessor #pred_idx from all 214b47af25099cac5c59795d6f1eb3b7cf9f962b32fChris Lattner // PHI nodes. Iterate over each PHI node fixing them up 215f878218c972dc570eb50e739c2ee2b9dd75ee5ddChris Lattner PHINode *PN; 21680f4d88a97e1b925c2ea67f932dd9c3ce1df1f8dChris Lattner for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ) { 21780f4d88a97e1b925c2ea67f932dd9c3ce1df1f8dChris Lattner ++II; 218280a6e607d8eb7401749a92db624a82de47da777Nick Lewycky PN->removeIncomingValue(Pred, false); 219a83ba0f5c934e2cdbb5724cab365ecc0b5aae6c6Nate Begeman // If all incoming values to the Phi are the same, we can replace the Phi 220a83ba0f5c934e2cdbb5724cab365ecc0b5aae6c6Nate Begeman // with that value. 22190245d4cbb7816ef21f038ec5ef7e01971283436Owen Anderson Value* PNV = 0; 22290245d4cbb7816ef21f038ec5ef7e01971283436Owen Anderson if (!DontDeleteUselessPHIs && (PNV = PN->hasConstantValue())) { 2231325b42a7dc38e99e1aa3531395d1678b31d3c55Chris Lattner PN->replaceAllUsesWith(PNV); 2241325b42a7dc38e99e1aa3531395d1678b31d3c55Chris Lattner PN->eraseFromParent(); 2251325b42a7dc38e99e1aa3531395d1678b31d3c55Chris Lattner } 226a83ba0f5c934e2cdbb5724cab365ecc0b5aae6c6Nate Begeman } 227b47af25099cac5c59795d6f1eb3b7cf9f962b32fChris Lattner } 228b47af25099cac5c59795d6f1eb3b7cf9f962b32fChris Lattner} 229b47af25099cac5c59795d6f1eb3b7cf9f962b32fChris Lattner 230009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner 2310f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// splitBasicBlock - This splits a basic block into two at the specified 2320f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// instruction. Note that all instructions BEFORE the specified iterator stay 233fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman/// as part of the original basic block, an unconditional branch is added to 2340f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// the new BB, and the rest of the instructions in the BB are moved to the new 2350f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// BB, including the old terminator. This invalidates the iterator. 2360f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 237fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman/// Note that this only works on well formed basic blocks (must have a 2380f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// terminator), and 'I' must not be the end of instruction list (which would 2390f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// cause a degenerate basic block to be formed, having a terminator inside of 240fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman/// the basic block). 2410f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 2426e0d1cb30957a636c53158d3089e6fb88348a57aDaniel DunbarBasicBlock *BasicBlock::splitBasicBlock(iterator I, const Twine &BBName) { 243009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!"); 244fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman assert(I != InstList.end() && 2459d80930e950214d026afd3a3d18cda32629efdb9Jeff Cohen "Trying to get me to create degenerate basic block!"); 246009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner 247fed90b6d097d50881afb45e4d79f430db66dd741Dan Gohman BasicBlock *InsertBefore = next(Function::iterator(this)) 248fed90b6d097d50881afb45e4d79f430db66dd741Dan Gohman .getNodePtrUnchecked(); 2491d0be15f89cb5056e20e2d24faa8d6afb1573bcaOwen Anderson BasicBlock *New = BasicBlock::Create(getContext(), BBName, 2501d0be15f89cb5056e20e2d24faa8d6afb1573bcaOwen Anderson getParent(), InsertBefore); 251009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner 252f2c3106866137b0c06e99f453a83d9558c0c6934Chris Lattner // Move all of the specified instructions from the original basic block into 253f2c3106866137b0c06e99f453a83d9558c0c6934Chris Lattner // the new basic block. 254f2c3106866137b0c06e99f453a83d9558c0c6934Chris Lattner New->getInstList().splice(New->end(), this->getInstList(), I, end()); 255009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner 256009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner // Add a branch instruction to the newly formed basic block. 257051a950000e21935165db56695e35bade668193bGabor Greif BranchInst::Create(New, this); 258e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner 259e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner // Now we must loop through all of the successors of the New block (which 260e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner // _were_ the successors of the 'this' block), and update any PHI nodes in 261e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner // successors. If there were PHI nodes in the successors, then they need to 262e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner // know that incoming branches will be from New, not from Old. 263e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner // 2641c9ab515de41707c8e04a51694a50479068e891dChris Lattner for (succ_iterator I = succ_begin(New), E = succ_end(New); I != E; ++I) { 265e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner // Loop over any phi nodes in the basic block, updating the BB field of 266e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner // incoming values... 267e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner BasicBlock *Successor = *I; 268f878218c972dc570eb50e739c2ee2b9dd75ee5ddChris Lattner PHINode *PN; 269e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner for (BasicBlock::iterator II = Successor->begin(); 2709bf2a926cbdf05c5b412ec35e72908a08a4cf34bChris Lattner (PN = dyn_cast<PHINode>(II)); ++II) { 271e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner int IDX = PN->getBasicBlockIndex(this); 272e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner while (IDX != -1) { 273e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner PN->setIncomingBlock((unsigned)IDX, New); 274e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner IDX = PN->getBasicBlockIndex(this); 275e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner } 276e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner } 277e8e320d2faa997605c76a7c3ab9e9b4fb578e8c0Chris Lattner } 278009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner return New; 279009505452b713ed2e3a8e99c5545a6e721c65495Chris Lattner} 280