revert r84754, it isn't the right approach. Edwin, please propose
patches for fixes like this instead of committing them directly.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84799 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 1088684..9147a99 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -1985,42 +1985,6 @@
return 0;
}
-// Check whether all the operands of the PHI dominate the PHI node,
-// knowing that the PHI's operands either dominate BB, or are defined in the BB.
-static bool checkPHI(PHINode *PN, BasicBlock *BB)
-{
- BasicBlock *phiBB = PN->getParent();
- for (unsigned i=0;i<PN->getNumIncomingValues();i++) {
- Instruction *I = dyn_cast<Instruction>(PN->getIncomingValue(i));
- if (!I)
- continue;
- BasicBlock *pBB = I->getParent();
- if (pBB == BB) {
- // another PHI in same BB is always before PN (PN is last phi).
- if (isa<PHINode>(I))
- continue;
- // An instruction in the same BB, and not a phi, this is after PN.
- return false;
- }
- if (phiBB == BB)
- continue;
- // We don't have dominator info, so just check that the instruction
- // is not defined in on of the BB on the unique path between BB and phiBB.
- // If there is no such unique path, or pBB equals to one of the BBs on that
- // path we know that this operand doesn't dominate the PHI node.
- BasicBlock *B = PN->getIncomingBlock(i);
- while ((B = B->getUniquePredecessor())) {
- if (pBB == B)
- return false;
- if (B == phiBB)
- break;
- }
- // No unique path -> doesn't dominate
- if (!B)
- return false;
- }
- return true;
-}
/// FoldOpIntoPhi - Given a binary operator, cast instruction, or select which
/// has a PHI node as operand #0, see if we can fold the instruction into the
@@ -2072,13 +2036,9 @@
// Okay, we can do the transformation: create the new PHI node.
PHINode *NewPN = PHINode::Create(I.getType(), "");
NewPN->reserveOperandSpace(PN->getNumOperands()/2);
- // We must the PHI node as the last PHI, because it may use one of the other
- // PHIs.
- BasicBlock::iterator BBIt = PN;
- while (isa<PHINode>(BBIt)) ++BBIt;
- InsertNewInstBefore(NewPN, *BBIt);
+ InsertNewInstBefore(NewPN, *PN);
+ NewPN->takeName(PN);
- SmallVector<Instruction*, 2> tmpWorklist;
// Next, add all of the operands to the PHI.
if (SelectInst *SI = dyn_cast<SelectInst>(&I)) {
// We only currently try to fold the condition of a select when it is a phi,
@@ -2098,7 +2058,7 @@
InV = SelectInst::Create(PN->getIncomingValue(i), TrueVInPred,
FalseVInPred,
"phitmp", NonConstBB->getTerminator());
- tmpWorklist.push_back(cast<Instruction>(InV));
+ Worklist.Add(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, ThisBB);
}
@@ -2124,7 +2084,8 @@
NonConstBB->getTerminator());
else
llvm_unreachable("Unknown binop!");
- tmpWorklist.push_back(cast<Instruction>(InV));
+
+ Worklist.Add(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, PN->getIncomingBlock(i));
}
@@ -2140,26 +2101,11 @@
InV = CastInst::Create(CI->getOpcode(), PN->getIncomingValue(i),
I.getType(), "phitmp",
NonConstBB->getTerminator());
- tmpWorklist.push_back(cast<Instruction>(InV));
+ Worklist.Add(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, PN->getIncomingBlock(i));
}
}
- // The PHI's operands must dominate the PHI, if we can't prove that
- // undo this transformation.
- if (!checkPHI(NewPN, I.getParent())) {
- Worklist.Remove(NewPN);
- NewPN->eraseFromParent();
- while (!tmpWorklist.empty()) {
- tmpWorklist.pop_back_val()->eraseFromParent();
- }
- return 0;
- }
- while (!tmpWorklist.empty()) {
- Worklist.Add(tmpWorklist.pop_back_val());
- }
- NewPN->takeName(PN);
- Worklist.Add(PN);
return ReplaceInstUsesWith(I, NewPN);
}