From ab876b6ce86fa69412177a8958c5dea1f45950e0 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 18 Aug 2010 03:14:36 +0000
Subject: [PATCH] Fix PR7755: knowing something about an inval for a pred from
 the LHS should disable reconsidering that pred on the RHS.  However, knowing
 something about the pred on the RHS shouldn't disable subsequent additions on
 the RHS from happening.

llvm-svn: 111349
---
 lib/Transforms/Scalar/JumpThreading.cpp | 12 ++++--------
 test/Transforms/JumpThreading/crash.ll  | 24 ++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index c2caf48b761..b17f80d39c0 100644
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -341,25 +341,21 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
       else
         InterestingVal = ConstantInt::getFalse(I->getContext());
       
+      SmallPtrSet<BasicBlock*, 4> LHSKnownBBs;
+      
       // Scan for the sentinel.  If we find an undef, force it to the
       // interesting value: x|undef -> true and x&undef -> false.
       for (unsigned i = 0, e = LHSVals.size(); i != e; ++i)
         if (LHSVals[i].first == InterestingVal || LHSVals[i].first == 0) {
           Result.push_back(LHSVals[i]);
           Result.back().first = InterestingVal;
+          LHSKnownBBs.insert(LHSVals[i].second);
         }
       for (unsigned i = 0, e = RHSVals.size(); i != e; ++i)
         if (RHSVals[i].first == InterestingVal || RHSVals[i].first == 0) {
           // If we already inferred a value for this block on the LHS, don't
           // re-add it.
-          bool HasValue = false;
-          for (unsigned r = 0, e = Result.size(); r != e; ++r)
-            if (Result[r].second == RHSVals[i].second) {
-              HasValue = true;
-              break;
-            }
-          
-          if (!HasValue) {
+          if (!LHSKnownBBs.count(RHSVals[i].second)) {
             Result.push_back(RHSVals[i]);
             Result.back().first = InterestingVal;
           }
diff --git a/test/Transforms/JumpThreading/crash.ll b/test/Transforms/JumpThreading/crash.ll
index 4fe94e5ea0c..cfd90424312 100644
--- a/test/Transforms/JumpThreading/crash.ll
+++ b/test/Transforms/JumpThreading/crash.ll
@@ -436,4 +436,28 @@ for.cond1040:                                     ; preds = %for.body1044, %for.
   ret void
 }
 
+; PR7755
+define void @test16(i1 %c, i1 %c2, i1 %c3, i1 %c4) nounwind ssp {
+entry:
+  %cmp = icmp sgt i32 undef, 1                    ; <i1> [#uses=1]
+  br i1 %c, label %land.end, label %land.rhs
+
+land.rhs:                                         ; preds = %entry
+  br i1 %c2, label %lor.lhs.false.i, label %land.end
+
+lor.lhs.false.i:                                  ; preds = %land.rhs
+  br i1 %c3, label %land.end, label %land.end
+
+land.end:                            
+  %0 = phi i1 [ true, %entry ], [ false, %land.rhs ], [false, %lor.lhs.false.i], [false, %lor.lhs.false.i] ; <i1> [#uses=1]
+  %cmp12 = and i1 %cmp, %0 
+  %xor1 = xor i1 %cmp12, %c4
+  br i1 %xor1, label %if.then, label %if.end
+
+if.then:                      
+  ret void
+
+if.end:                       
+  ret void
+}