revert 132986 to see if the bots go green.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132988 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 5 insertions, 64 deletions

diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index b43884ebf2..719cd264f6 100644
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -799,22 +799,14 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
 
   // First find blocks with no successors.
   MergePotentials.clear();
-  for (MachineFunction::iterator I = MF.begin(), E = MF.end();
-       I != E && MergePotentials.size() < TailMergeThreshold; ++I) {
-    if (TriedMerging.count(I))
-      continue;
+  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
     if (I->succ_empty())
       MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(I), I));
   }
 
-  // If this is a large problem, avoid visiting the same basic blocks
-  // multiple times.
-  if (MergePotentials.size() == TailMergeThreshold)
-    for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
-      TriedMerging.insert(MergePotentials[i].getBlock());
-
   // See if we can do any tail merging on those.
-  if (MergePotentials.size() >= 2)
+  if (MergePotentials.size() < TailMergeThreshold &&
+      MergePotentials.size() >= 2)
     MadeChange |= TryTailMergeBlocks(NULL, NULL);
 
   // Look at blocks (IBB) with multiple predecessors (PBB).
@@ -838,17 +830,15 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
 
   for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end();
        I != E; ++I) {
-    if (I->pred_size() >= 2) {
+    if (I->pred_size() >= 2 && I->pred_size() < TailMergeThreshold) {
       SmallPtrSet<MachineBasicBlock *, 8> UniquePreds;
       MachineBasicBlock *IBB = I;
       MachineBasicBlock *PredBB = prior(I);
       MergePotentials.clear();
       for (MachineBasicBlock::pred_iterator P = I->pred_begin(),
                                             E2 = I->pred_end();
-           P != E2 && MergePotentials.size() < TailMergeThreshold; ++P) {
+           P != E2; ++P) {
         MachineBasicBlock *PBB = *P;
-        if (TriedMerging.count(PBB))
-          continue;
         // Skip blocks that loop to themselves, can't tail merge these.
         if (PBB == IBB)
           continue;
@@ -901,12 +891,6 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
           MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(PBB), *P));
         }
       }
-      // If this is a large problem, avoid visiting the same basic blocks
-      // multiple times.
-      if (MergePotentials.size() == TailMergeThreshold)
-        for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
-          TriedMerging.insert(MergePotentials[i].getBlock());
-
       if (MergePotentials.size() >= 2)
         MadeChange |= TryTailMergeBlocks(IBB, PredBB);
       // Reinsert an unconditional branch if needed.
diff --git a/lib/CodeGen/BranchFolding.h b/lib/CodeGen/BranchFolding.h
index 4ed42c0346..4daf4ecfe5 100644
--- a/lib/CodeGen/BranchFolding.h
+++ b/lib/CodeGen/BranchFolding.h
@@ -10,7 +10,6 @@
 #ifndef LLVM_CODEGEN_BRANCHFOLDING_HPP
 #define LLVM_CODEGEN_BRANCHFOLDING_HPP
 
-#include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include <vector>
 
@@ -48,7 +47,6 @@ namespace llvm {
     };
     typedef std::vector<MergePotentialsElt>::iterator MPIterator;
     std::vector<MergePotentialsElt> MergePotentials;
-    SmallPtrSet<const MachineBasicBlock*, 2> TriedMerging;
 
     class SameTailElt {
       MPIterator MPIter;
diff --git a/test/CodeGen/X86/tail-threshold.ll b/test/CodeGen/X86/tail-threshold.ll
deleted file mode 100644
index 17e22d9dd9..0000000000
--- a/test/CodeGen/X86/tail-threshold.ll
+++ /dev/null
@@ -1,41 +0,0 @@
-; RUN: llc %s -stats -tail-merge-threshold 2 -o /dev/null |& FileCheck %s
-
-; Test that we still do some merging if a block has more than
-; tail-merge-threshold predecessors.
-
-; CHECK: 2 branchfolding   - Number of block tails merged
-
-declare void @bar()
-
-define void @foo(i32 %xxx) {
-entry:
-  switch i32 %xxx, label %bb4 [
-    i32 0, label %bb0
-    i32 1, label %bb1
-    i32 2, label %bb2
-    i32 3, label %bb3
-  ]
-
-bb0:
-  call void @bar()
-  br label %bb5
-
-bb1:
- call void @bar()
- br label %bb5
-
-bb2:
-  call void @bar()
-  br label %bb5
-
-bb3:
-  call void @bar()
-  br label %bb5
-
-bb4:
-  call void @bar()
-  br label %bb5
-
-bb5:
-  ret void
-}