[llvm] r300662 - Revert r300657 due to crashes in stage2 of bootstraps:

[Chandler Carruth via llvm-commits]

Author: chandlerc
Date: Wed Apr 19 01:23:20 2017
New Revision: 300662

URL: http://llvm.org/viewvc/llvm-project?rev=300662&view=rev
Log:
Revert r300657 due to crashes in stage2 of bootstraps:
http://lab.llvm.org:8011/builders/clang-with-lto-ubuntu/builds/2476/steps/build-stage2-LLVMgold.so/logs/stdio
http://bb.pgr.jp/builders/clang-3stage-x86_64-linux/builds/15036/steps/build_llvmclang/logs/stdio

I've updated the commit thread, reverting to get the bots back to green.

Original commit summary:
[JumpThread] We want to fold (not thread) when all predecessor go to single BB's successor.

Modified:
    llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
    llvm/trunk/test/Transforms/JumpThreading/basic.ll

Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=300662&r1=300661&r2=300662&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Wed Apr 19 01:23:20 2017
@@ -1289,33 +1289,6 @@ bool JumpThreadingPass::ProcessThreadabl
   if (PredToDestList.empty())
     return false;
 
-  // If all the predecessors go to a single known successor, we want to fold,
-  // not thread. By doing so, we do not need to duplicate the current block and
-  // also miss potential opportunities in case we don't/can't duplicate.
-  if (OnlyDest && OnlyDest != MultipleDestSentinel) {
-    if (PredToDestList.size() ==
-        (size_t)std::distance(pred_begin(BB), pred_end(BB))) {
-      for (BasicBlock *SuccBB : successors(BB)) {
-        if (SuccBB != OnlyDest)
-          SuccBB->removePredecessor(BB, true); // This is unreachable successor.
-      }
-
-      // Finally update the terminator.
-      TerminatorInst *Term = BB->getTerminator();
-      BranchInst::Create(OnlyDest, Term);
-      Term->eraseFromParent();
-
-      // If the condition is now dead due to the removal of the old terminator,
-      // erase it.
-      auto *CondInst = dyn_cast<Instruction>(Cond);
-      if (CondInst && CondInst->use_empty())
-        CondInst->eraseFromParent();
-      // FIXME: in case this instruction is defined in the current BB and it
-      // resolves to a single value from all predecessors, we can do RAUW.
-      return true;
-    }
-  }
-
   // Determine which is the most common successor.  If we have many inputs and
   // this block is a switch, we want to start by threading the batch that goes
   // to the most popular destination first.  If we only know about one

Modified: llvm/trunk/test/Transforms/JumpThreading/basic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/JumpThreading/basic.ll?rev=300662&r1=300661&r2=300662&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/JumpThreading/basic.ll (original)
+++ llvm/trunk/test/Transforms/JumpThreading/basic.ll Wed Apr 19 01:23:20 2017
@@ -4,95 +4,6 @@ declare i32 @f1()
 declare i32 @f2()
 declare void @f3()
 
-; Make sure we can fold this branch ... We will not be able to thread it as
-; L0 is too big to duplicate. L2 is the unreachable block here.
-;
-; CHECK-LABEL: @test_br_folding_not_threading(
-; CHECK: L1:
-; CHECK: call i32 @f2()
-; CHECK: call void @f3()
-; CHECK-NEXT: ret void
-; CHECK-NOT: br
-; CHECK: L3:
-define void @test_br_folding_not_threading(i1 %cond) nounwind {
-entry:
-  br i1 %cond, label %L0, label %L3 
-L0:
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  br i1 %cond, label %L1, label %L2 
-
-L1:
-  call void @f3()
-  ret void
-L2:
-  call void @f3()
-  ret void
-L3:
-  call void @f3()
-  ret void
-}
-
-
-; Make sure we can fold this branch ... We will not be able to thread it as
-; L0 is too big to duplicate. L2 is the unreachable block here.
-; With more than 1 predecessors.
-;
-; CHECK-LABEL: @test_br_folding_not_threading_multiple_preds(
-; CHECK: L1:
-; CHECK: call i32 @f2()
-; CHECK: call void @f3()
-; CHECK-NEXT: ret void
-; CHECK-NOT: br
-; CHECK: L3:
-define void @test_br_folding_not_threading_multiple_preds(i1 %condx, i1 %cond) nounwind {
-entry:
-  br i1 %condx, label %X0, label %X1
-
-X0:
-  br i1 %cond, label %L0, label %L3 
-
-X1:
-  br i1 %cond, label %L0, label %L3 
-
-L0:
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  call i32 @f2()
-  br i1 %cond, label %L1, label %L2 
-
-L1:
-  call void @f3()
-  ret void
-L2:
-  call void @f3()
-  ret void
-L3:
-  call void @f3()
-  ret void
-}
-
 define i32 @test1(i1 %cond) {
 ; CHECK-LABEL: @test1(