[llvm] [VPlan] Make canonical IV part of the region (PR #156262)

[via llvm-commits]

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@@ -870,6 +894,24 @@ void VPRegionBlock::dissolveToCFGLoop() {
   VPBlockUtils::connectBlocks(ExitingLatch, Header);
 }
 
+VPInstruction *VPRegionBlock::getCanonicalIVIncrement() {
+  auto *ExitingLatch = cast<VPBasicBlock>(getExiting());
+  VPValue *CanIV = getCanonicalIV();
+  assert(CanIV && "Expected a canonical IV");
+
+  auto *ExitingTerm = ExitingLatch->getTerminator();
+  VPInstruction *CanIVInc = nullptr;
+  if (match(ExitingTerm,
+            m_BranchOnCount(m_VPInstruction(CanIVInc), m_VPValue()))) {
+    assert(match(CanIVInc,
+                 m_c_Add(m_CombineOr(m_Specific(CanIV),
+                                     m_c_Add(m_Specific(CanIV), m_LiveIn())),
+                         m_VPValue())) &&
+           "invalid existing IV increment");
+  }
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ayalz wrote:

ok to only have an assert under an if?

https://github.com/llvm/llvm-project/pull/156262