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Factor the logic for testing whether a basic block is viable for code

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extraction into a public interface. Also clean it up and apply it more
consistently such that we check for landing pads *anywhere* in the
extracted code, not just in single-block extraction.

This will be used to guide decisions in passes that are planning to
eventually perform a round of code extraction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156114 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2012-05-03 22:26:53 +00:00
parent cb348b9b45
commit 9f7af7b748
2 changed files with 29 additions and 14 deletions
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8
include/llvm/Transforms/Utils/FunctionUtils.h
View File

@ -23,6 +23,14 @@ namespace llvm {
class Function;
class Loop;
/// \brief Test whether a basic block is a viable candidate for extraction.
///
/// This tests whether a particular basic block is viable for extraction into
/// a separate function. It can be used to prune code extraction eagerly
/// rather than waiting for one of the Extract* methods below to reject
/// a request.
bool isBlockViableForExtraction(const BasicBlock &BB);
/// ExtractCodeRegion - Rip out a sequence of basic blocks into a new
/// function.
///

35
lib/Transforms/Utils/CodeExtractor.cpp
View File

@ -756,24 +756,31 @@ ExtractCodeRegion(ArrayRef<BasicBlock*> code) {
}
bool CodeExtractor::isEligible(ArrayRef<BasicBlock*> code) {
// Deny a single basic block that's a landing pad block.
if (code.size() == 1 && code[0]->isLandingPad())
return false;
for (ArrayRef<BasicBlock*>::iterator I = code.begin(), E = code.end();
I != E; ++I)
if (!isBlockViableForExtraction(**I))
return false;
// Deny code region if it contains allocas or vastarts.
for (ArrayRef<BasicBlock*>::iterator BB = code.begin(), e=code.end();
BB != e; ++BB)
for (BasicBlock::const_iterator I = (*BB)->begin(), Ie = (*BB)->end();
I != Ie; ++I)
if (isa<AllocaInst>(*I))
return false;
else if (const CallInst *CI = dyn_cast<CallInst>(I))
if (const Function *F = CI->getCalledFunction())
if (F->getIntrinsicID() == Intrinsic::vastart)
return false;
return true;
}
bool llvm::isBlockViableForExtraction(const BasicBlock &BB) {
// Landing pads must be in the function where they were inserted for cleanup.
if (BB.isLandingPad())
return false;
// Don't hoist code containing allocas, invokes, or vastarts.
for (BasicBlock::const_iterator I = BB.begin(), E = BB.end(); I != E; ++I) {
if (isa<AllocaInst>(I) || isa<InvokeInst>(I))
return false;
if (const CallInst *CI = dyn_cast<CallInst>(I))
if (const Function *F = CI->getCalledFunction())
if (F->getIntrinsicID() == Intrinsic::vastart)
return false;
}
return true;
}
/// ExtractCodeRegion - Slurp a sequence of basic blocks into a brand new
/// function.