1 //===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==//
2 //
3 // This family of functions perform manipulations on basic blocks, and
4 // instructions contained within basic blocks.
5 //
6 //===----------------------------------------------------------------------===//
7 
8 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
9 #include "llvm/Function.h"
10 #include "llvm/Instruction.h"
11 #include <algorithm>
12 
13 // ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
14 // with a value, then remove and delete the original instruction.
15 //
16 void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
17                           BasicBlock::iterator &BI, Value *V) {
18   Instruction *I = *BI;
19   // Replaces all of the uses of the instruction with uses of the value
20   I->replaceAllUsesWith(V);
21 
22   // Remove the unneccesary instruction now...
23   BIL.remove(BI);
24 
25   // Make sure to propogate a name if there is one already...
26   if (I->hasName() && !V->hasName())
27     V->setName(I->getName(), BIL.getParent()->getSymbolTable());
28 
29   // Remove the dead instruction now...
30   delete I;
31 }
32 
33 
34 // ReplaceInstWithInst - Replace the instruction specified by BI with the
35 // instruction specified by I.  The original instruction is deleted and BI is
36 // updated to point to the new instruction.
37 //
38 void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
39                          BasicBlock::iterator &BI, Instruction *I) {
40   assert(I->getParent() == 0 &&
41          "ReplaceInstWithInst: Instruction already inserted into basic block!");
42 
43   // Insert the new instruction into the basic block...
44   BI = BIL.insert(BI, I)+1;  // Increment BI to point to instruction to delete
45 
46   // Replace all uses of the old instruction, and delete it.
47   ReplaceInstWithValue(BIL, BI, I);
48 
49   // Move BI back to point to the newly inserted instruction
50   --BI;
51 }
52 
53 // ReplaceInstWithInst - Replace the instruction specified by From with the
54 // instruction specified by To.  Note that this is slower than providing an
55 // iterator directly, because the basic block containing From must be searched
56 // for the instruction.
57 //
58 void ReplaceInstWithInst(Instruction *From, Instruction *To) {
59   BasicBlock *BB = From->getParent();
60   BasicBlock::InstListType &BIL = BB->getInstList();
61   BasicBlock::iterator BI = find(BIL.begin(), BIL.end(), From);
62   assert(BI != BIL.end() && "Inst not in it's parents BB!");
63   ReplaceInstWithInst(BIL, BI, To);
64 }
65 
66 // InsertInstBeforeInst - Insert 'NewInst' into the basic block that 'Existing'
67 // is already in, and put it right before 'Existing'.  This instruction should
68 // only be used when there is no iterator to Existing already around.  The
69 // returned iterator points to the new instruction.
70 //
71 BasicBlock::iterator InsertInstBeforeInst(Instruction *NewInst,
72                                           Instruction *Existing) {
73   BasicBlock *BB = Existing->getParent();
74   BasicBlock::InstListType &BIL = BB->getInstList();
75   BasicBlock::iterator BI = find(BIL.begin(), BIL.end(), Existing);
76   assert(BI != BIL.end() && "Inst not in it's parents BB!");
77   return BIL.insert(BI, NewInst);
78 }
79 
80