From f478951b0eeed2f8a9e39254f65458c9325dab91 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 16 Dec 2008 07:10:09 +0000
Subject: [PATCH] fix PR3217: fully cached queries need to be verified against
 the visited set before they are used.  If used, their blocks need to be added
 to the visited set so that subsequent queries don't use conflicting pointer
 values in the cache result blocks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61080 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/MemoryDependenceAnalysis.cpp     | 22 ++++++++++++++-
 .../Transforms/GVN/2008-12-15-CacheVisited.ll | 28 +++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 test/Transforms/GVN/2008-12-15-CacheVisited.ll

diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp
index a5bfeee7bc1..6818da83ba7 100644
--- a/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -601,10 +601,30 @@ getNonLocalPointerDepFromBB(Value *Pointer, uint64_t PointeeSize,
   // If we have valid cached information for exactly the block we are
   // investigating, just return it with no recomputation.
   if (CacheInfo->first == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) {
+    // We have a fully cached result for this query then we can just return the
+    // cached results and populate the visited set.  However, we have to verify
+    // that we don't already have conflicting results for these blocks.  Check
+    // to ensure that if a block in the results set is in the visited set that
+    // it was for the same pointer query.
+    if (!Visited.empty()) {
+      for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
+           I != E; ++I) {
+        DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->first);
+        if (VI == Visited.end() || VI->second == Pointer) continue;
+        
+        // We have a pointer mismatch in a block.  Just return clobber, saying
+        // that something was clobbered in this result.  We could also do a
+        // non-fully cached query, but there is little point in doing this.
+        return true;
+      }
+    }
+    
     for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
-         I != E; ++I)
+         I != E; ++I) {
+      Visited.insert(std::make_pair(I->first, Pointer));
       if (!I->second.isNonLocal())
         Result.push_back(*I);
+    }
     ++NumCacheCompleteNonLocalPtr;
     return false;
   }
diff --git a/test/Transforms/GVN/2008-12-15-CacheVisited.ll b/test/Transforms/GVN/2008-12-15-CacheVisited.ll
new file mode 100644
index 00000000000..b547003b25e
--- /dev/null
+++ b/test/Transforms/GVN/2008-12-15-CacheVisited.ll
@@ -0,0 +1,28 @@
+; RUN: llvm-as < %s | opt -gvn | llvm-dis
+; Cached results must be added to and verified against the visited sets.
+; PR3217
+
+define fastcc void @gen_field_die(i32* %decl) nounwind {
+entry:
+	br i1 false, label %bb203, label %bb202
+
+bb202:		; preds = %entry
+	unreachable
+
+bb203:		; preds = %entry
+	%tmp = getelementptr i32* %decl, i32 1		; <i32*> [#uses=1]
+	%tmp1 = load i32* %tmp, align 4		; <i32> [#uses=0]
+	br i1 false, label %bb207, label %bb204
+
+bb204:		; preds = %bb203
+	%tmp2 = getelementptr i32* %decl, i32 1		; <i32*> [#uses=1]
+	br label %bb208
+
+bb207:		; preds = %bb203
+	br label %bb208
+
+bb208:		; preds = %bb207, %bb204
+	%iftmp.1374.0.in = phi i32* [ null, %bb207 ], [ %tmp2, %bb204 ]		; <i32*> [#uses=1]
+	%iftmp.1374.0 = load i32* %iftmp.1374.0.in		; <i32> [#uses=0]
+	unreachable
+}