// Check to see if this value is already used in the memory instruction's
// block. If so, it's already live into the block at the very least, so we
// can reasonably fold it.
- BasicBlock *MemBB = MemoryInst->getParent();
- for (Value::use_iterator UI = Val->use_begin(), E = Val->use_end();
- UI != E; ++UI)
- // We know that uses of arguments and instructions have to be instructions.
- if (cast<Instruction>(*UI)->getParent() == MemBB)
- return true;
-
- return false;
+ return Val->isUsedInBasicBlock(MemoryInst->getParent());
}
/// isUsedInBasicBlock - Return true if this value is used in the specified
/// basic block.
bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
+ // Start by scanning over the instructions looking for a use before we start
+ // the expensive use iteration.
+ unsigned MaxBlockSize = 3;
+ for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+ if (std::find(I->op_begin(), I->op_end(), this) != I->op_end())
+ return true;
+ if (MaxBlockSize-- == 0) // If the block is larger fall back to use_iterator
+ break;
+ }
+
+ if (MaxBlockSize != 0) // We scanned the entire block and found no use.
+ return false;
+
for (const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) {
const Instruction *User = dyn_cast<Instruction>(*I);
if (User && User->getParent() == BB)