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Code refactoring.

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llvm-svn: 100262
This commit is contained in:
Evan Cheng 2010-04-03 02:23:43 +00:00
parent c2f273b52d
commit b56fbc400f
1 changed files with 34 additions and 36 deletions
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70
lib/Transforms/Scalar/LoopUnswitch.cpp
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@ -415,46 +415,44 @@ bool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val) {
Function *F = loopHeader->getParent();
// If the condition is trivial, always unswitch. There is no code growth for
// this case.
if (!IsTrivialUnswitchCondition(LoopCond)) {
// Check to see if it would be profitable to unswitch current loop.
// Do not do non-trivial unswitch while optimizing for size.
if (OptimizeForSize || F->hasFnAttr(Attribute::OptimizeForSize))
return false;
// FIXME: This is overly conservative because it does not take into
// consideration code simplification opportunities and code that can
// be shared by the resultant unswitched loops.
CodeMetrics Metrics;
for (Loop::block_iterator I = currentLoop->block_begin(),
E = currentLoop->block_end();
I != E; ++I)
Metrics.analyzeBasicBlock(*I);
// Limit the number of instructions to avoid causing significant code
// expansion, and the number of basic blocks, to avoid loops with
// large numbers of branches which cause loop unswitching to go crazy.
// This is a very ad-hoc heuristic.
if (Metrics.NumInsts > Threshold ||
Metrics.NumBlocks * 5 > Threshold ||
Metrics.NeverInline) {
DEBUG(dbgs() << "NOT unswitching loop %"
<< currentLoop->getHeader()->getName() << ", cost too high: "
<< currentLoop->getBlocks().size() << "\n");
return false;
}
}
Constant *CondVal;
BasicBlock *ExitBlock;
Constant *CondVal = 0;
BasicBlock *ExitBlock = 0;
if (IsTrivialUnswitchCondition(LoopCond, &CondVal, &ExitBlock)) {
// If the condition is trivial, always unswitch. There is no code growth
// for this case.
UnswitchTrivialCondition(currentLoop, LoopCond, CondVal, ExitBlock);
} else {
UnswitchNontrivialCondition(LoopCond, Val, currentLoop);
return true;
}
// Check to see if it would be profitable to unswitch current loop.
// Do not do non-trivial unswitch while optimizing for size.
if (OptimizeForSize || F->hasFnAttr(Attribute::OptimizeForSize))
return false;
// FIXME: This is overly conservative because it does not take into
// consideration code simplification opportunities and code that can
// be shared by the resultant unswitched loops.
CodeMetrics Metrics;
for (Loop::block_iterator I = currentLoop->block_begin(),
E = currentLoop->block_end();
I != E; ++I)
Metrics.analyzeBasicBlock(*I);
// Limit the number of instructions to avoid causing significant code
// expansion, and the number of basic blocks, to avoid loops with
// large numbers of branches which cause loop unswitching to go crazy.
// This is a very ad-hoc heuristic.
if (Metrics.NumInsts > Threshold ||
Metrics.NumBlocks * 5 > Threshold ||
Metrics.NeverInline) {
DEBUG(dbgs() << "NOT unswitching loop %"
<< currentLoop->getHeader()->getName() << ", cost too high: "
<< currentLoop->getBlocks().size() << "\n");
return false;
}
UnswitchNontrivialCondition(LoopCond, Val, currentLoop);
return true;
}