[llvm] r346823 - Revert r346810 "Preserve loop metadata when splitting exit blocks"

[Reid Kleckner via llvm-commits]

Author: rnk
Date: Tue Nov 13 17:47:32 2018
New Revision: 346823

URL: http://llvm.org/viewvc/llvm-project?rev=346823&view=rev
Log:
Revert r346810 "Preserve loop metadata when splitting exit blocks"

It broke the Windows self-host:
http://lab.llvm.org:8011/builders/clang-x64-windows-msvc/builds/1457

Removed:
    llvm/trunk/test/Transforms/LoopSimplify/preserve-llvm-loop-metadata2.ll
Modified:
    llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp

Modified: llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp?rev=346823&r1=346822&r2=346823&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopUtils.cpp Tue Nov 13 17:47:32 2018
@@ -74,41 +74,9 @@ bool llvm::formDedicatedExitBlocks(Loop
     if (IsDedicatedExit)
       return false;
 
-    // With nested loops, the inner loop might exit to the header of an
-    // enclosing loop, and the in-loop-predecessor is a latch for that
-    // enclosing loop. If we insert a block between the latch and the header,
-    // that block becomes the new latch. Any loop metadata from the old latch
-    // needs to be moved to the new one.
-    MDNode *OuterLoopMD = nullptr;
-
-    // If the exit block is a header of a different loop, get that loop's
-    // metadata before we split the block.
-    if (LI->isLoopHeader(BB))
-      OuterLoopMD = LI->getLoopFor(BB)->getLoopID();
-
     auto *NewExitBB = SplitBlockPredecessors(
         BB, InLoopPredecessors, ".loopexit", DT, LI, nullptr, PreserveLCSSA);
 
-    // If OuterLoopMD is non-null, we know that the exit block BB is a
-    // loop header for a different loop, with metadata on its back edges.
-    // If NewExitBB is a member of that loop, then NewExitBB is a latch,
-    // and the loop's metadata needs to be copied to NewExitBB.
-    if (NewExitBB && OuterLoopMD &&
-        LI->getLoopFor(NewExitBB) == LI->getLoopFor(BB)) {
-      // The preds of NewExitBB are all former latches of the outer loop.
-      // Remove their metadata.
-      for (auto *PredLoopBB : InLoopPredecessors) {
-        Instruction *TI = PredLoopBB->getTerminator();
-        // All the latches should have the same metadata (ensured by
-        // getLoopID()).
-        assert(TI->getMetadata(LLVMContext::MD_loop) == OuterLoopMD &&
-               "exit edge to other loop doesn't contain expected metadata");
-        TI->setMetadata(LLVMContext::MD_loop, nullptr);
-      }
-      NewExitBB->getTerminator()->setMetadata(LLVMContext::MD_loop,
-                                              OuterLoopMD);
-    }
-
     if (!NewExitBB)
       LLVM_DEBUG(
           dbgs() << "WARNING: Can't create a dedicated exit block for loop: "

Removed: llvm/trunk/test/Transforms/LoopSimplify/preserve-llvm-loop-metadata2.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopSimplify/preserve-llvm-loop-metadata2.ll?rev=346822&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopSimplify/preserve-llvm-loop-metadata2.ll (original)
+++ llvm/trunk/test/Transforms/LoopSimplify/preserve-llvm-loop-metadata2.ll (removed)
@@ -1,48 +0,0 @@
-; RUN: opt -S -loop-simplify < %s | FileCheck %s
-
-; Two-loop nest with llvm.loop metadata on each loop.
-; inner.header exits to outer.header. inner.header is a latch for the outer
-; loop, and contains the outer loop's metadata.
-; After loop-simplify, a new block "outer.header.loopexit" is created between
-; inner.header and outer.header. The metadata from inner.header must be moved
-; to the new block, as the new block becomes the outer loop latch.
-; The metadata on the inner loop's latch should be untouched.
-
-; CHECK: outer.header.loopexit:
-; CHECK-NEXT: llvm.loop [[UJAMTAG:.*]]
-; CHECK-NOT: br i1 {{.*}}, label {{.*}}, label %outer.header.loopexit, !llvm.loop
-; CHECK: br label %inner.header, !llvm.loop [[UNROLLTAG:.*]]
-
-; CHECK: distinct !{[[UJAMTAG]], [[UJAM:.*]]}
-; CHECK: [[UJAM]] = !{!"llvm.loop.unroll_and_jam.count", i32 17}
-; CHECK: distinct !{[[UNROLLTAG]], [[UNROLL:.*]]}
-; CHECK: [[UNROLL]] = !{!"llvm.loop.unroll.count", i32 1}
-
-
-define dso_local void @loopnest() local_unnamed_addr #0 {
-entry:
-  br label %outer.header
-
-outer.header:                                         ; preds = %inner.header, %entry
-  %ii.0 = phi i64 [ 2, %entry ], [ %add, %inner.header ]
-  %cmp = icmp ult i64 %ii.0, 64
-  br i1 %cmp, label %inner.header, label %outer.header.cleanup
-
-outer.header.cleanup:                                 ; preds = %outer.header
-  ret void
-
-inner.header:                                        ; preds = %outer.header, %inner.body
-  %j.0 = phi i64 [ %add10, %inner.body ], [ %ii.0, %outer.header ]
-  %add = add nuw nsw i64 %ii.0, 16
-  %cmp2 = icmp ult i64 %j.0, %add
-  br i1 %cmp2, label %inner.body, label %outer.header, !llvm.loop !2
-
-inner.body:                                        ; preds = %inner.header
-  %add10 = add nuw nsw i64 %j.0, 1
-  br label %inner.header, !llvm.loop !4
-}
-
-!2 = distinct !{!2, !3}
-!3 = !{!"llvm.loop.unroll_and_jam.count", i32 17}
-!4 = distinct !{!4, !5}
-!5 = !{!"llvm.loop.unroll.count", i32 1}