[PATCH] [Jump-Threading] Fixed jump threading hang issues (PR15386, PR15851)

[Dinesh Dwivedi]

updated test case

http://reviews.llvm.org/D3991

Files:
  lib/Transforms/Scalar/JumpThreading.cpp
  test/Transforms/JumpThreading/pr15851_hang.ll

Index: lib/Transforms/Scalar/JumpThreading.cpp
===================================================================
--- lib/Transforms/Scalar/JumpThreading.cpp
+++ lib/Transforms/Scalar/JumpThreading.cpp
@@ -160,10 +160,12 @@
 
   FindLoopHeaders(F);
 
-  bool Changed, EverChanged = false;
+  unsigned UpdatedBBCount;
+  SmallPtrSet<BasicBlock *, 16> UpdatedBB;
   do {
-    Changed = false;
+    UpdatedBBCount = UpdatedBB.size();
     for (Function::iterator I = F.begin(), E = F.end(); I != E;) {
+      bool Changed = false;
       BasicBlock *BB = I;
       // Thread all of the branches we can over this block.
       while (ProcessBlock(BB))
@@ -180,7 +182,7 @@
         LoopHeaders.erase(BB);
         LVI->eraseBlock(BB);
         DeleteDeadBlock(BB);
-        Changed = true;
+        UpdatedBB.insert(BB);
         continue;
       }
 
@@ -214,12 +216,13 @@
         if (ErasedFromLoopHeaders)
           LoopHeaders.insert(BB);
       }
+      if (Changed)
+        UpdatedBB.insert(BB);
     }
-    EverChanged |= Changed;
-  } while (Changed);
+  } while (UpdatedBBCount < UpdatedBB.size());
 
   LoopHeaders.clear();
-  return EverChanged;
+  return UpdatedBBCount > 0;
 }
 
 /// getJumpThreadDuplicationCost - Return the cost of duplicating this block to
Index: test/Transforms/JumpThreading/pr15851_hang.ll
===================================================================
--- /dev/null
+++ test/Transforms/JumpThreading/pr15851_hang.ll
@@ -0,0 +1,38 @@
+; RUN: timeout 10s opt -S -jump-threading < %s | FileCheck %s
+
+; CHECK-LABEL: @f(
+; CHECK-LABEL: for.cond1
+; CHECK: phi i32 [ %div, %for.body ], [ %div, %land.rhs ], [ 0, %for.body.thread ]
+; CHECK: br i1 %cmp, label %for.body, label %for.cond1.thread
+; CHECK: for.cond1.thread
+; CHECK-NEXT: br label %for.body.thread
+; CHECK: for.body.thread
+; CHECK-NEXT: br label %for.cond1
+; CHECK: for.body
+; CHECK: phi i32 [ %inc, %for.cond1 ]
+; CHECK-NOT: for.inc
+
+define void @f() {
+entry:
+ call void @f()
+ unreachable
+
+for.cond1: ; preds = %for.cond1, %for.inc
+ %i.0 = phi i32 [ %inc, %for.inc ], [ 0, %for.cond1 ]
+ %cmp = icmp slt i32 %i.0, 2
+ br i1 %cmp, label %for.body, label %for.cond1
+
+for.body: ; preds = %for.cond1
+ %div = sdiv i32 %i.0, 2
+ %i.0.off = add i32 %i.0, 1
+ %0 = icmp ugt i32 %i.0.off, 2
+ br i1 %0, label %land.rhs, label %for.inc
+
+land.rhs: ; preds = %for.body
+ store i32 0, i32* undef, align 4
+ br label %for.inc
+
+for.inc: ; preds = %for.body
+ %inc = add nsw i32 %div, 1
+ br label %for.cond1
+}
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D3991.10272.patch
Type: text/x-patch
Size: 2518 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20140610/85fcb9cf/attachment.bin>