[NPM] Properly reset parent loop after loop passes

This fixes https://bugs.llvm.org/show_bug.cgi?id=49185

When `NDEBUG` is not set, `LPMUpdater` checks if the added loops have the same parent loop as the current one in `addSiblingLoops`.
If multiple loop passes are executed through `LoopPassManager`, `U.ParentL` will be the same across all passes.
However, the parent loop might change after running a loop pass, resulting in assertion failures in subsequent passes.

This patch resets `U.ParentL` after running individual loop passes in `LoopPassManager`.

Reviewed By: asbirlea, ychen

Differential Revision: https://reviews.llvm.org/D96727

Author: TaWeiTu

llvm/include/llvm/Transforms/Scalar/LoopPassManager.h

@@ -271,6 +271,12 @@ class LPMUpdater {
       SkipCurrentLoop = true;
   }
 
+  void setParentLoop(Loop *L) {
+#ifndef NDEBUG
+    ParentL = L;
+#endif
+  }
+
   /// Loop passes should use this method to indicate they have added new child
   /// loops of the current loop.
   ///

llvm/lib/Transforms/Scalar/LoopPassManager.cpp

@@ -114,6 +114,11 @@ LoopPassManager::runWithLoopNestPasses(Loop &L, LoopAnalysisManager &AM,
     // Check if the current pass preserved the loop-nest object or not.
     IsLoopNestPtrValid &= PassPA->getChecker<LoopNestAnalysis>().preserved();
 
+    // After running the loop pass, the parent loop might change and we need to
+    // notify the updater, otherwise U.ParentL might gets outdated and triggers
+    // assertion failures in addSiblingLoops and addChildLoops.
+    U.setParentLoop(L.getParentLoop());
+
     // FIXME: Historically, the pass managers all called the LLVM context's
     // yield function here. We don't have a generic way to acquire the
     // context and it isn't yet clear what the right pattern is for yielding
@@ -158,6 +163,11 @@ LoopPassManager::runWithoutLoopNestPasses(Loop &L, LoopAnalysisManager &AM,
     // aggregate preserved set for this pass manager.
     PA.intersect(std::move(*PassPA));
 
+    // After running the loop pass, the parent loop might change and we need to
+    // notify the updater, otherwise U.ParentL might gets outdated and triggers
+    // assertion failures in addSiblingLoops and addChildLoops.
+    U.setParentLoop(L.getParentLoop());
+
     // FIXME: Historically, the pass managers all called the LLVM context's
     // yield function here. We don't have a generic way to acquire the
     // context and it isn't yet clear what the right pattern is for yielding

llvm/test/Transforms/Util/pr49185.ll

@@ -0,0 +1,95 @@
+; REQUIRES: asserts
+; RUN: opt -S -passes='default<O3>' %s
+%struct0 = type { i64, i64, i32, i64, i32 }
+%struct1 = type { i32 }
+%union0 = type { i32 }
+%union1 = type { i16 }
+%union2 = type { i32 }
+
+@g_6 = external dso_local global i32, align 1
+@g_60 = external dso_local global i16, align 1
+@g_79 = external dso_local global { i16, i16 }, align 1
+@g_315 = external dso_local global %struct0, align 1
+@g_359 = external dso_local global %struct0, align 1
+
+define dso_local i16 @main(i16 %argc, i16** %argv) #0 {
+entry:
+  %call2 = call i16 @func_1()
+  unreachable
+}
+
+define internal i16 @func_1() #0 {
+entry:
+  %call = call i16 @func_21(i32* undef, i32 undef, i32* undef)
+  ret i16 undef
+}
+
+define internal i16 @func_21(i32* %p_22, i32 %p_23, i32* %p_24) #0 {
+entry:
+  call void @func_34(%struct0* align 1 undef, i32 undef, i32 undef, i32* @g_6, %union0* byval(%union0) align 1 undef)
+  unreachable
+}
+
+define internal void @func_34(%struct0* %agg.result, i32 %p_35, i32 %p_36, i32* %p_37, %union0* %p_38) #0 {
+entry:
+  %p_37.addr = alloca i32*, align 1
+  %cleanup.dest.slot = alloca i32, align 1
+  store i32* %p_37, i32** %p_37.addr, align 1
+  br label %lbl_898
+
+lbl_898:                                          ; preds = %cleanup3097, %entry
+  br label %lbl_1111
+
+lbl_1111:                                         ; preds = %cleanup3097, %lbl_898
+  %0 = load i32, i32* getelementptr inbounds (%struct0, %struct0* @g_359, i32 0, i32 4), align 1
+  %tobool1833 = icmp ne i32 %0, 0
+  br i1 %tobool1833, label %land.rhs1834, label %land.end1851
+
+land.rhs1834:                                     ; preds = %lbl_1111
+  store i16 0, i16* @g_60, align 1
+  br label %land.end1851
+
+land.end1851:                                     ; preds = %land.rhs1834, %lbl_1111
+  %1 = load i32*, i32** %p_37.addr, align 1
+  %2 = load i32, i32* %1, align 1
+  %tobool2351 = icmp ne i32 %2, 0
+  br i1 %tobool2351, label %if.then2352, label %if.else3029
+
+if.then2352:                                      ; preds = %land.end1851
+  %3 = load i16, i16* getelementptr inbounds ({ i16, i16 }, { i16, i16 }* @g_79, i32 0, i32 0), align 1, !tbaa !1
+  %tobool3011 = icmp ne i16 %3, 0
+  call void @llvm.assume(i1 %tobool3011)
+  store i32 11, i32* %cleanup.dest.slot, align 1
+  br label %cleanup3097
+
+if.else3029:                                      ; preds = %land.end1851
+  store i32 3, i32* getelementptr inbounds (%struct0, %struct0* @g_315, i32 0, i32 4), align 1
+  store i32 132, i32* %cleanup.dest.slot, align 1
+  br label %cleanup3097
+
+cleanup3097:                                      ; preds = %if.else3029, %if.then2352
+  %cleanup.dest3113 = load i32, i32* %cleanup.dest.slot, align 1
+  switch i32 %cleanup.dest3113, label %cleanup3402 [
+    i32 132, label %lbl_1111
+    i32 11, label %lbl_898
+  ]
+
+cleanup3402:                                      ; preds = %cleanup3097
+  ret void
+}
+
+; Function Attrs: nofree nosync nounwind willreturn
+declare void @llvm.assume(i1 noundef) #4
+
+attributes #0 = { "use-soft-float"="false" }
+attributes #1 = { argmemonly nofree nosync nounwind willreturn }
+attributes #2 = { noinline }
+attributes #3 = { argmemonly nofree nosync nounwind willreturn writeonly }
+attributes #4 = { nofree nosync nounwind willreturn }
+
+!llvm.ident = !{!0}
+
+!0 = !{!"clang version 13.0.0"}
+!1 = !{!2, !2, i64 0}
+!2 = !{!"omnipotent char", !3, i64 0}
+!3 = !{!"Simple C/C++ TBAA"}