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Add a little heuristic to Value::isUsedInBasicBlock to speed it up for small basic blocks.
- Calling getUser in a loop is much more expensive than iterating over a few instructions. - Use it instead of the open-coded loop in AddrModeMatcher. - 5% speedup on ARMDisassembler.cpp Release builds. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145810 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -473,14 +473,7 @@ bool AddressingModeMatcher::ValueAlreadyLiveAtInst(Value *Val,Value *KnownLive1,
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// Check to see if this value is already used in the memory instruction's
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// block. If so, it's already live into the block at the very least, so we
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// can reasonably fold it.
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BasicBlock *MemBB = MemoryInst->getParent();
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for (Value::use_iterator UI = Val->use_begin(), E = Val->use_end();
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UI != E; ++UI)
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// We know that uses of arguments and instructions have to be instructions.
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if (cast<Instruction>(*UI)->getParent() == MemBB)
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return true;
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return false;
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return Val->isUsedInBasicBlock(MemoryInst->getParent());
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}
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@ -108,6 +108,19 @@ bool Value::hasNUsesOrMore(unsigned N) const {
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/// isUsedInBasicBlock - Return true if this value is used in the specified
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/// basic block.
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bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
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// Start by scanning over the instructions looking for a use before we start
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// the expensive use iteration.
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unsigned MaxBlockSize = 3;
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for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
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if (std::find(I->op_begin(), I->op_end(), this) != I->op_end())
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return true;
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if (MaxBlockSize-- == 0) // If the block is larger fall back to use_iterator
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break;
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}
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if (MaxBlockSize != 0) // We scanned the entire block and found no use.
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return false;
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for (const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) {
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const Instruction *User = dyn_cast<Instruction>(*I);
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if (User && User->getParent() == BB)
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