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Refactor some code into a function

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llvm-svn: 23603
This commit is contained in:
Chris Lattner 2005-10-03 01:04:44 +00:00
parent 5a865c8598
commit 6a5ace34da
1 changed files with 23 additions and 7 deletions
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30
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -310,6 +310,26 @@ static bool getSCEVStartAndStride(const SCEVHandle &SH, Loop *L,
return true;
}
/// IVUseShouldUsePostIncValue - We have discovered a "User" of an IV expression
/// and now we need to decide whether the user should use the preinc or post-inc
/// value. If this user should use the post-inc version of the IV, return true.
///
/// Choosing wrong here can break dominance properties (if we choose to use the
/// post-inc value when we cannot) or it can end up adding extra live-ranges to
/// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
/// should use the post-inc value).
static bool IVUseShouldUsePostIncValue(Instruction *User, Instruction *IV,
Loop *L, DominatorSet *DS) {
// If the user is in the loop, use the preinc value.
if (L->contains(User->getParent())) return false;
// Ok, the user is outside of the loop. If it is not dominated by the latch
// block, we have to use the preincremented value.
return DS->dominates(L->getLoopLatch(), User->getParent());
}
/// AddUsersIfInteresting - Inspect the specified instruction. If it is a
/// reducible SCEV, recursively add its users to the IVUsesByStride set and
/// return true. Otherwise, return false.
@ -353,18 +373,14 @@ bool LoopStrengthReduce::AddUsersIfInteresting(Instruction *I, Loop *L,
// Okay, we found a user that we cannot reduce. Analyze the instruction
// and decide what to do with it. If we are a use inside of the loop, use
// the value before incrementation, otherwise use it after incrementation.
if (L->contains(User->getParent()) ||
// Alternatively, if we are a use outside of the loop, but is not
// dominated by the latch block, we have to use the preincremented
// value.
!DS->dominates(L->getLoopLatch(), User->getParent())) {
IVUsesByStride[Stride].addUser(Start, User, I);
} else {
if (IVUseShouldUsePostIncValue(User, I, L, DS)) {
// The value used will be incremented by the stride more than we are
// expecting, so subtract this off.
SCEVHandle NewStart = SCEV::getMinusSCEV(Start, Stride);
IVUsesByStride[Stride].addUser(NewStart, User, I);
IVUsesByStride[Stride].Users.back().isUseOfPostIncrementedValue = true;
} else {
IVUsesByStride[Stride].addUser(Start, User, I);
}
}
}