[LoopVersioning] Add a check to see if the input loop is in LCSSA form

llvm/lib/Transforms/Utils/LoopVersioning.cpp

@@ -26,6 +26,7 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/Transforms/Utils/LoopUtils.h"
 #include "llvm/Transforms/Utils/ScalarEvolutionExpander.h"
 
 using namespace llvm;
@@ -278,6 +279,9 @@ bool runImpl(LoopInfo *LI, LoopAccessInfoManager &LAIs, DominatorTree *DT,
     if (!LAI.hasConvergentOp() &&
         (LAI.getNumRuntimePointerChecks() ||
          !LAI.getPSE().getPredicate().isAlwaysTrue())) {
+      if (!L->isLCSSAForm(*DT))
+        llvm::formLCSSARecursively(*L, *DT, LI, SE);
+
       LoopVersioning LVer(LAI, LAI.getRuntimePointerChecking()->getChecks(), L,
                           LI, DT, SE);
       LVer.versionLoop();

llvm/test/Transforms/LoopVersioning/crash-36998.ll

@@ -0,0 +1,57 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=loop-versioning -aa-pipeline='' -S < %s | FileCheck %s
+target triple = "x86_64-unknown-linux-gnu"
+
+@a = external global i16, align 1
+@b = external global i16, align 1
+@c = external global i16, align 1
+
+define void @f2() {
+; CHECK-LABEL: define void @f2() {
+; CHECK-NEXT:  [[FOR_BODY_LVER_CHECK:.*:]]
+; CHECK-NEXT:    [[BOUND0:%.*]] = icmp ult ptr @b, getelementptr inbounds nuw (i8, ptr @a, i64 2)
+; CHECK-NEXT:    [[BOUND1:%.*]] = icmp ult ptr @a, getelementptr inbounds nuw (i8, ptr @b, i64 2)
+; CHECK-NEXT:    [[FOUND_CONFLICT:%.*]] = and i1 [[BOUND0]], [[BOUND1]]
+; CHECK-NEXT:    br i1 [[FOUND_CONFLICT]], label %[[FOR_BODY_PH_LVER_ORIG:.*]], label %[[FOR_BODY_PH:.*]]
+; CHECK:       [[FOR_BODY_PH_LVER_ORIG]]:
+; CHECK-NEXT:    br label %[[FOR_BODY_LVER_ORIG:.*]]
+; CHECK:       [[FOR_BODY_LVER_ORIG]]:
+; CHECK-NEXT:    [[TMP0:%.*]] = load i16, ptr @a, align 1
+; CHECK-NEXT:    store i16 [[TMP0]], ptr @b, align 1
+; CHECK-NEXT:    [[INC_LVER_ORIG:%.*]] = add nsw i16 undef, 1
+; CHECK-NEXT:    br i1 false, label %[[FOR_BODY_LVER_ORIG]], label %[[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT:.*]]
+; CHECK:       [[FOR_BODY_PH]]:
+; CHECK-NEXT:    br label %[[FOR_BODY:.*]]
+; CHECK:       [[FOR_BODY]]:
+; CHECK-NEXT:    [[TMP1:%.*]] = load i16, ptr @a, align 1, !alias.scope [[META0:![0-9]+]]
+; CHECK-NEXT:    store i16 [[TMP1]], ptr @b, align 1, !alias.scope [[META3:![0-9]+]], !noalias [[META0]]
+; CHECK-NEXT:    [[INC:%.*]] = add nsw i16 undef, 1
+; CHECK-NEXT:    br i1 false, label %[[FOR_BODY]], label %[[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT1:.*]]
+; CHECK:       [[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT]]:
+; CHECK-NEXT:    [[INC_LCSSA_PH:%.*]] = phi i16 [ [[INC_LVER_ORIG]], %[[FOR_BODY_LVER_ORIG]] ]
+; CHECK-NEXT:    [[SPLIT2_PH:%.*]] = phi i16 [ [[INC_LVER_ORIG]], %[[FOR_BODY_LVER_ORIG]] ]
+; CHECK-NEXT:    br label %[[FOR_COND_FOR_END_CRIT_EDGE:.*]]
+; CHECK:       [[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT1]]:
+; CHECK-NEXT:    [[INC_LCSSA_PH2:%.*]] = phi i16 [ [[INC]], %[[FOR_BODY]] ]
+; CHECK-NEXT:    [[SPLIT2_PH3:%.*]] = phi i16 [ [[INC]], %[[FOR_BODY]] ]
+; CHECK-NEXT:    br label %[[FOR_COND_FOR_END_CRIT_EDGE]]
+; CHECK:       [[FOR_COND_FOR_END_CRIT_EDGE]]:
+; CHECK-NEXT:    [[INC_LCSSA:%.*]] = phi i16 [ [[INC_LCSSA_PH]], %[[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT]] ], [ [[INC_LCSSA_PH2]], %[[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT1]] ]
+; CHECK-NEXT:    [[SPLIT2:%.*]] = phi i16 [ [[SPLIT2_PH]], %[[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT]] ], [ [[SPLIT2_PH3]], %[[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT1]] ]
+; CHECK-NEXT:    store i16 [[INC_LCSSA]], ptr @c, align 1
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %0 = load i16, ptr @a, align 1
+  store i16 %0, ptr @b, align 1
+  %inc = add nsw i16 undef, 1
+  br i1 false, label %for.body, label %for.cond.for.end_crit_edge
+
+for.cond.for.end_crit_edge:                       ; preds = %for.body
+  %split2 = phi i16 [ %inc, %for.body ]
+  store i16 %inc, ptr @c, align 1
+  ret void
+}