[llvm] [VPlan] Add extra checks for LoopForBB. NFC. (PR #132306)

[via llvm-commits]

https://github.com/offsake updated https://github.com/llvm/llvm-project/pull/132306

>From f96bc6134fbc4e9bb74d082a6c2d7c022f1860e1 Mon Sep 17 00:00:00 2001
From: SergeyZ <sergey.i.zverev at intel.com>
Date: Wed, 19 Mar 2025 16:07:57 -0700
Subject: [PATCH 1/2] [VPlan] Add extra checks for LoopForBB. NFC.

Adding the checks for LoopForBB not being nullptr before try to dereference it.
---
 llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp b/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp
index 4b8a2420b3037..467c83395b812 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp
@@ -379,7 +379,7 @@ void PlainCFGBuilder::buildPlainCFG(
     VPRegionBlock *Region = VPBB->getParent();
     Loop *LoopForBB = LI->getLoopFor(BB);
     // Set VPBB predecessors in the same order as they are in the incoming BB.
-    if (!isHeaderBB(BB, LoopForBB)) {
+    if (LoopForBB && !isHeaderBB(BB, LoopForBB)) {
       setVPBBPredsFromBB(VPBB, BB);
     } else if (Region) {
       // BB is a loop header and there's a corresponding region, set the
@@ -390,7 +390,7 @@ void PlainCFGBuilder::buildPlainCFG(
     // Create VPInstructions for BB.
     createVPInstructionsForVPBB(VPBB, BB);
 
-    if (BB == TheLoop->getLoopLatch()) {
+    if (LoopForBB && BB == TheLoop->getLoopLatch()) {
       VPBasicBlock *HeaderVPBB = getOrCreateVPBB(LoopForBB->getHeader());
       VPBlockUtils::connectBlocks(VPBB, HeaderVPBB);
       continue;
@@ -423,7 +423,7 @@ void PlainCFGBuilder::buildPlainCFG(
     BasicBlock *IRSucc1 = BI->getSuccessor(1);
     VPBasicBlock *Successor0 = getOrCreateVPBB(IRSucc0);
     VPBasicBlock *Successor1 = getOrCreateVPBB(IRSucc1);
-    if (BB == LoopForBB->getLoopLatch()) {
+    if (LoopForBB && BB == LoopForBB->getLoopLatch()) {
       // For a latch we need to set the successor of the region rather than that
       // of VPBB and it should be set to the exit, i.e., non-header successor,
       // except for the top region, which is handled elsewhere.

>From 78063b2e424b191f8d614e3c67b361fce7c5862b Mon Sep 17 00:00:00 2001
From: SergeyZ <sergey.i.zverev at intel.com>
Date: Mon, 31 Mar 2025 10:36:39 -0700
Subject: [PATCH 2/2] [NFC][VPlan] Delete redundant check.

---
 .../Transforms/Vectorize/VPlanHCFGBuilder.cpp | 22 +++++++++----------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp b/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp
index 467c83395b812..9dad45ce1c3ce 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp
@@ -379,7 +379,7 @@ void PlainCFGBuilder::buildPlainCFG(
     VPRegionBlock *Region = VPBB->getParent();
     Loop *LoopForBB = LI->getLoopFor(BB);
     // Set VPBB predecessors in the same order as they are in the incoming BB.
-    if (LoopForBB && !isHeaderBB(BB, LoopForBB)) {
+    if (!isHeaderBB(BB, LoopForBB)) {
       setVPBBPredsFromBB(VPBB, BB);
     } else if (Region) {
       // BB is a loop header and there's a corresponding region, set the
@@ -390,7 +390,7 @@ void PlainCFGBuilder::buildPlainCFG(
     // Create VPInstructions for BB.
     createVPInstructionsForVPBB(VPBB, BB);
 
-    if (LoopForBB && BB == TheLoop->getLoopLatch()) {
+    if (BB == TheLoop->getLoopLatch()) {
       VPBasicBlock *HeaderVPBB = getOrCreateVPBB(LoopForBB->getHeader());
       VPBlockUtils::connectBlocks(VPBB, HeaderVPBB);
       continue;
@@ -423,7 +423,7 @@ void PlainCFGBuilder::buildPlainCFG(
     BasicBlock *IRSucc1 = BI->getSuccessor(1);
     VPBasicBlock *Successor0 = getOrCreateVPBB(IRSucc0);
     VPBasicBlock *Successor1 = getOrCreateVPBB(IRSucc1);
-    if (LoopForBB && BB == LoopForBB->getLoopLatch()) {
+    if (BB == LoopForBB->getLoopLatch()) {
       // For a latch we need to set the successor of the region rather than that
       // of VPBB and it should be set to the exit, i.e., non-header successor,
       // except for the top region, which is handled elsewhere.
@@ -437,15 +437,13 @@ void PlainCFGBuilder::buildPlainCFG(
 
     // Don't connect any blocks outside the current loop except the latch for
     // now. The latch is handled above.
-    if (LoopForBB) {
-      if (!LoopForBB->contains(IRSucc0)) {
-        VPBB->setOneSuccessor(Successor1);
-        continue;
-      }
-      if (!LoopForBB->contains(IRSucc1)) {
-        VPBB->setOneSuccessor(Successor0);
-        continue;
-      }
+    if (!LoopForBB->contains(IRSucc0)) {
+      VPBB->setOneSuccessor(Successor1);
+      continue;
+    }
+    if (!LoopForBB->contains(IRSucc1)) {
+      VPBB->setOneSuccessor(Successor0);
+      continue;
     }
 
     VPBB->setTwoSuccessors(Successor0, Successor1);