Revert "[LoopInfo] Limit the iterations to check whether a loop has dedicated

exits"

Get a better approach in https://reviews.llvm.org/D68107 to solve the problem.
Revert the initial patch and will commit the new one soon.

This reverts commit rL372990.

llvm-svn: 373044

4 files changed, 2 insertions, 124 deletions

diff --git a/llvm/include/llvm/Analysis/LoopInfo.h b/llvm/include/llvm/Analysis/LoopInfo.h
index 8fe81589abb..abf3863b060 100644
--- a/llvm/include/llvm/Analysis/LoopInfo.h
+++ b/llvm/include/llvm/Analysis/LoopInfo.h
@@ -269,9 +269,6 @@ public:
 
   /// Return true if no exit block for the loop has a predecessor that is
   /// outside the loop.
-  /// Return false if a non-dedicated successor is found or it cannot finish
-  /// the check within MaxDedicateExitIterations iterations so return false
-  /// conservatively.
   bool hasDedicatedExits() const;
 
   /// Return all unique successor blocks of this loop.
diff --git a/llvm/include/llvm/Analysis/LoopInfoImpl.h b/llvm/include/llvm/Analysis/LoopInfoImpl.h
index acea41a9d0a..2f38dde7b3a 100644
--- a/llvm/include/llvm/Analysis/LoopInfoImpl.h
+++ b/llvm/include/llvm/Analysis/LoopInfoImpl.h
@@ -23,10 +23,6 @@
 
 namespace llvm {
 
-// Max number of loop iterations to check whether a loop is a dedicated
-// exit loop.
-extern cl::opt<uint64_t> MaxDedicateExitIterations;
-
 //===----------------------------------------------------------------------===//
 // APIs for simple analysis of the loop. See header notes.
 
@@ -91,16 +87,10 @@ bool LoopBase<BlockT, LoopT>::hasDedicatedExits() const {
   // within the loop.
   SmallVector<BlockT *, 4> ExitBlocks;
   getExitBlocks(ExitBlocks);
-  uint64_t Iterations = 0;
-  for (BlockT *EB : ExitBlocks) {
-    for (BlockT *Predecessor : children<Inverse<BlockT *>>(EB)) {
+  for (BlockT *EB : ExitBlocks)
+    for (BlockT *Predecessor : children<Inverse<BlockT *>>(EB))
       if (!contains(Predecessor))
         return false;
-      Iterations++;
-    }
-    if (Iterations > MaxDedicateExitIterations)
-      return false;
-  }
   // All the requirements are met.
   return true;
 }
diff --git a/llvm/lib/Analysis/LoopInfo.cpp b/llvm/lib/Analysis/LoopInfo.cpp
index c37a5c48e50..1dc63a3c333 100644
--- a/llvm/lib/Analysis/LoopInfo.cpp
+++ b/llvm/lib/Analysis/LoopInfo.cpp
@@ -54,13 +54,6 @@ static cl::opt<bool, true>
     VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo),
                     cl::Hidden, cl::desc("Verify loop info (time consuming)"));
 
-namespace llvm {
-cl::opt<uint64_t> MaxDedicateExitIterations(
-    "max-dedicate-exit-iterations", cl::Hidden, cl::init(100000),
-    cl::desc("Max number of loop iterations to check whether a loop is a "
-             "dedicated exit loop. "));
-}
-
 //===----------------------------------------------------------------------===//
 // Loop implementation
 //
diff --git a/llvm/test/Transforms/LICM/loop-max-dedicated-exit-iterations.ll b/llvm/test/Transforms/LICM/loop-max-dedicated-exit-iterations.ll
deleted file mode 100644
index 421f2d191b1..00000000000
--- a/llvm/test/Transforms/LICM/loop-max-dedicated-exit-iterations.ll
+++ /dev/null
@@ -1,102 +0,0 @@
-; RUN: opt -S -licm -max-dedicate-exit-iterations=5 < %s | FileCheck %s
-; RUN: opt -S -licm -max-dedicate-exit-iterations=100 < %s | FileCheck %s -check-prefixes=SINK
-; RUN: opt -S -passes='require<opt-remark-emit>,loop(licm)' -max-dedicate-exit-iterations=5 < %s | FileCheck %s
-; RUN: opt -S -passes='require<opt-remark-emit>,loop(licm)' -max-dedicate-exit-iterations=100 < %s | FileCheck %s -check-prefixes=SINK
-; Code sink in LICM requires the loop has dedicated exits. Use code sink
-; in LICM to verify max-dedicate-exit-iterations is functioning.
-
-@_ZL1m = internal global i64 0, align 8
-@.str = private unnamed_addr constant [13 x i8] c"hello = %ld\0A\00", align 1
-@llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_2.cc, i8* null }]
-
-declare dso_local i64 @_Z3goov() local_unnamed_addr #0
-
-; Function Attrs: argmemonly nounwind willreturn
-declare {}* @llvm.invariant.start.p0i8(i64 immarg, i8* nocapture)
-
-; Function Attrs: uwtable
-define dso_local void @_Z3fool(i64 %a) local_unnamed_addr {
-entry:
-  %cmp18.old.old.old.old.old = icmp slt i64 %a, 5
-  %cmp14.old.old.old.old = icmp slt i64 %a, 4
-  %cmp10.old.old.old = icmp slt i64 %a, 3
-  %cmp6.old.old = icmp slt i64 %a, 2
-  %cmp2.old = icmp slt i64 %a, 1
-  %cmp = icmp slt i64 %a, 0
-; Check load cannot be sinked out of loop when max-dedicate-exit-iterations=5
-; and hasDedicatedExits return false, so it is hoisted out of loop.
-; CHECK: load i64, i64* @_ZL1m, align 8
-; CHECK: br label %do.body
-; CHECK: do.body:
-  br label %do.body
-
-do.body:                                          ; preds = %do.body.backedge, %entry
-  %t0 = load i64, i64* @_ZL1m, align 8, !tbaa !2
-  %call = tail call i64 @_Z3goov()
-  switch i64 %call, label %do.cond [
-    i64 0, label %sw.bb
-    i64 1, label %sw.bb1
-    i64 2, label %sw.bb5
-    i64 3, label %sw.bb9
-    i64 4, label %sw.bb13
-    i64 5, label %sw.bb17
-  ]
-
-sw.bb:                                            ; preds = %do.body
-  br i1 %cmp, label %Done, label %do.body.backedge
-
-sw.bb1:                                           ; preds = %do.body
-  br i1 %cmp2.old, label %Done, label %do.body.backedge
-
-sw.bb5:                                           ; preds = %do.body
-  br i1 %cmp6.old.old, label %Done, label %do.body.backedge
-
-sw.bb9:                                           ; preds = %do.body
-  br i1 %cmp10.old.old.old, label %Done, label %do.body.backedge
-
-sw.bb13:                                          ; preds = %do.body
-  br i1 %cmp14.old.old.old.old, label %Done, label %do.body.backedge
-
-sw.bb17:                                          ; preds = %do.body
-  br i1 %cmp18.old.old.old.old.old, label %Done, label %do.body.backedge
-
-do.cond:                                          ; preds = %do.body
-  %cmp21.old.old.old.old.old.old = icmp slt i64 %call, 10000
-  br i1 %cmp21.old.old.old.old.old.old, label %do.body.backedge, label %Done
-
-do.body.backedge:                                 ; preds = %do.cond, %sw.bb17, %sw.bb13, %sw.bb9, %sw.bb5, %sw.bb1, %sw.bb
-  br label %do.body
-
-Done:                                             ; preds = %sw.bb, %sw.bb1, %sw.bb5, %sw.bb9, %sw.bb13, %sw.bb17, %do.cond
-; Check load is sinked out of loop when max-dedicate-exit-iterations=100
-; and hasDedicatedExits return true.
-; SINK: Done:
-; SINK: load i64, i64* @_ZL1m, align 8
-; SINK-NEXT: tail call {{.*}} @printf
-  %call22 = tail call i32 (i8*, ...) @printf(i8* nonnull dereferenceable(1) getelementptr inbounds ([13 x i8], [13 x i8]* @.str, i64 0, i64 0), i64 %t0)
-  ret void
-}
-
-; Function Attrs: nofree nounwind
-declare dso_local i32 @printf(i8* nocapture readonly, ...) local_unnamed_addr
-
-; Function Attrs: uwtable
-define internal void @_GLOBAL__sub_I_2.cc() section ".text.startup" {
-entry:
-  %call.i = tail call i64 @_Z3goov()
-  store i64 %call.i, i64* @_ZL1m, align 8, !tbaa !2
-  %t0 = tail call {}* @llvm.invariant.start.p0i8(i64 8, i8* bitcast (i64* @_ZL1m to i8*))
-  ret void
-}
-
-attributes #0 = { readonly }
-
-!llvm.module.flags = !{!0}
-!llvm.ident = !{!1}
-
-!0 = !{i32 1, !"wchar_size", i32 4}
-!1 = !{!"clang version 10.0.0 (trunk 372630) (llvm/trunk 372631)"}
-!2 = !{!3, !3, i64 0}
-!3 = !{!"long", !4, i64 0}
-!4 = !{!"omnipotent char", !5, i64 0}
-!5 = !{!"Simple C++ TBAA"}