[llvm] [VPlan] Connect (MemRuntime|SCEV)Check blocks as VPlan transform (NFC). (PR #143879)

[via llvm-commits]

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@@ -9349,6 +9259,48 @@ void LoopVectorizationPlanner::adjustRecipesForReductions(
   VPlanTransforms::runPass(VPlanTransforms::clearReductionWrapFlags, *Plan);
 }
 
+void LoopVectorizationPlanner::addRuntimeChecks(
+    VPlan &Plan, GeneratedRTChecks &RTChecks) const {
+  SmallVector<std::pair<VPValue *, VPIRBasicBlock *>> Checks;
+  const auto &[SCEVCheckCond, SCEVCheckBlock] = RTChecks.emitSCEVChecks();
+  if (SCEVCheckBlock) {
+    assert((!CM.OptForSize ||
+            CM.Hints->getForce() == LoopVectorizeHints::FK_Enabled) &&
+           "Cannot SCEV check stride or overflow when optimizing for size");
+    Checks.emplace_back(Plan.getOrAddLiveIn(SCEVCheckCond),
+                        Plan.createVPIRBasicBlock(SCEVCheckBlock));
+  }
+  const auto &[MemCheckCond, MemCheckBlock] = RTChecks.emitMemRuntimeChecks();
+  if (MemCheckBlock) {
+    // VPlan-native path does not do any analysis for runtime checks
+    // currently.
+    assert((!EnableVPlanNativePath || OrigLoop->isInnermost()) &&
+           "Runtime checks are not supported for outer loops yet");
+
+    if (CM.OptForSize) {
+      assert(
+          CM.Hints->getForce() == LoopVectorizeHints::FK_Enabled &&
+          "Cannot emit memory checks when optimizing for size, unless forced "
+          "to vectorize.");
+      ORE->emit([&]() {
+        return OptimizationRemarkAnalysis(DEBUG_TYPE, "VectorizationCodeSize",
+                                          OrigLoop->getStartLoc(),
+                                          OrigLoop->getHeader())
+               << "Code-size may be reduced by not forcing "
+                  "vectorization, or by source-code modifications "
+                  "eliminating the need for runtime checks "
+                  "(e.g., adding 'restrict').";
+      });
+    }
+    Checks.emplace_back(Plan.getOrAddLiveIn(MemCheckCond),
+                        Plan.createVPIRBasicBlock(MemCheckBlock));
+  }
+
+  VPlanTransforms::connectCheckBlocks(
+      Plan, Checks,
+      hasBranchWeightMD(*OrigLoop->getLoopLatch()->getTerminator()));
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ayalz wrote:

Better call `attachCheckBlock()` given each pair of cond and check blocks separately, twice, above?

Perhaps "attach" is more accurate than "add" or "connect", as this transformation wraps existing IR check conditions and blocks (held detached from original IR, and detached from VPlan until now) in VPValues and VPIRBBs, as when forming the initial VPlan from IR, rather than connecting existing VPlan entities together, or adding completely new entities to VPlan.

https://github.com/llvm/llvm-project/pull/143879