================
@@ -271,35 +276,51 @@ static void ConnectEpilog(Loop *L, Value *ModVal,
BasicBlock *NewExit,
NewExit);
// Now PHIs should look like:
// NewExit:
- // PN = PHI [I, Latch], [poison, PreHeader]
+ // PN = PHI [I, Latch]
// ...
// Exit:
// EpilogPN = PHI [PN, NewExit], [VMap[I], EpilogLatch]
}
- // Create PHI nodes at NewExit (from the unrolling loop Latch and PreHeader).
- // Update corresponding PHI nodes in epilog loop.
+ // Create PHI nodes at NewExit (from the unrolling loop Latch) and at
+ // EpilogPreHeader (from PreHeader and NewExit). Update corresponding PHI
+ // nodes in epilog loop.
for (BasicBlock *Succ : successors(Latch)) {
// Skip this as we already updated phis in exit blocks.
if (!L->contains(Succ))
continue;
+
+ // Succ here appears to always be just L->getHeader(). Otherwise, how do
we
+ // know its corresponding epilog block (from VMap) is EpilogHeader and thus
+ // EpilogPreHeader is the right incoming block for VPN, as set below?
+ // TODO: Can we thus avoid the enclosing loop over successors?
+ assert(Succ == L->getHeader() &&
+ "Expect only non-loop successor of latch to be header");
+
for (PHINode &PN : Succ->phis()) {
- // Add new PHI nodes to the loop exit block and update epilog
- // PHIs with the new PHI values.
- PHINode *NewPN = PHINode::Create(PN.getType(), 2, PN.getName() + ".unr");
- NewPN->insertBefore(NewExit->getFirstNonPHIIt());
- // Adding a value to the new PHI node from the unrolling loop preheader.
- NewPN->addIncoming(PN.getIncomingValueForBlock(NewPreHeader), PreHeader);
- // Adding a value to the new PHI node from the unrolling loop latch.
- NewPN->addIncoming(PN.getIncomingValueForBlock(Latch), Latch);
+ // Add new PHI nodes to the loop exit block.
+ PHINode *NewPN0 = PHINode::Create(PN.getType(), 1, PN.getName() +
".unr");
----------------
mtrofin wrote:
do you need a phi if all you have is 1 incoming value?
also, a nit: could you please add an argument comment for what `1` and then
further below, `2`, are?
https://github.com/llvm/llvm-project/pull/156549
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