Fix a crash in Dependency Analysis.

This crash in Dependency analysis is because we assume here that in case of UsefulGEP
both source and destination have the same number of operands which may not be true.
This incorrect assumption results in crash while populating Pairs. Fix the same.

This crash was observed during lnt regression for code such as-
  struct s{
    int A[10][10];
    int C[10][10][10]; 
  } S;
  void dep_constraint_crash_test(int k,int N)  {
     for( int i=0;i<N;i++)
       for( int j=0;j<N;j++)
         S.A[0][0] = S.C[0][0][k];
  }
Review: http://reviews.llvm.org/D8162

llvm-svn: 231784

2 files changed, 57 insertions, 6 deletions

diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index b3a6f6f47c0..3dcfcb839ad 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -3346,9 +3346,9 @@ DependenceAnalysis::depends(Instruction *Src, Instruction *Dst,
     DEBUG(dbgs() << "    SrcPtrSCEV = " << *SrcPtrSCEV << "\n");
     DEBUG(dbgs() << "    DstPtrSCEV = " << *DstPtrSCEV << "\n");
 
-    UsefulGEP =
-      isLoopInvariant(SrcPtrSCEV, LI->getLoopFor(Src->getParent())) &&
-      isLoopInvariant(DstPtrSCEV, LI->getLoopFor(Dst->getParent()));
+    UsefulGEP = isLoopInvariant(SrcPtrSCEV, LI->getLoopFor(Src->getParent())) &&
+                isLoopInvariant(DstPtrSCEV, LI->getLoopFor(Dst->getParent())) &&
+                (SrcGEP->getNumOperands() == DstGEP->getNumOperands());
   }
   unsigned Pairs = UsefulGEP ? SrcGEP->idx_end() - SrcGEP->idx_begin() : 1;
   SmallVector<Subscript, 4> Pair(Pairs);
@@ -3773,9 +3773,9 @@ const  SCEV *DependenceAnalysis::getSplitIteration(const Dependence &Dep,
       SrcGEP->getPointerOperandType() == DstGEP->getPointerOperandType()) {
     const SCEV *SrcPtrSCEV = SE->getSCEV(SrcGEP->getPointerOperand());
     const SCEV *DstPtrSCEV = SE->getSCEV(DstGEP->getPointerOperand());
-    UsefulGEP =
-      isLoopInvariant(SrcPtrSCEV, LI->getLoopFor(Src->getParent())) &&
-      isLoopInvariant(DstPtrSCEV, LI->getLoopFor(Dst->getParent()));
+    UsefulGEP = isLoopInvariant(SrcPtrSCEV, LI->getLoopFor(Src->getParent())) &&
+                isLoopInvariant(DstPtrSCEV, LI->getLoopFor(Dst->getParent())) &&
+                (SrcGEP->getNumOperands() == DstGEP->getNumOperands());
   }
   unsigned Pairs = UsefulGEP ? SrcGEP->idx_end() - SrcGEP->idx_begin() : 1;
   SmallVector<Subscript, 4> Pair(Pairs);
diff --git a/llvm/test/Analysis/DependenceAnalysis/UsefulGEP.ll b/llvm/test/Analysis/DependenceAnalysis/UsefulGEP.ll
new file mode 100644
index 00000000000..83c43cfca64
--- /dev/null
+++ b/llvm/test/Analysis/DependenceAnalysis/UsefulGEP.ll
@@ -0,0 +1,51 @@
+; RUN: opt < %s -analyze -basicaa -da
+;; Check this doesn't crash.
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+;; struct s {
+;;   int A[10][10];
+;;   int C[10][10][10]; 
+;; } S;
+
+;; void dep_constraint_crash_test(int k,int N) {
+;;   for( int i=0;i<N;i++)
+;;     for( int j=0;j<N;j++)
+;;       S.A[0][0] = S.C[0][0][k];
+;; }
+
+
+%struct.s = type { [10 x [10 x i32]], [10 x [10 x [10 x i32]]] }
+
+@S = common global %struct.s zeroinitializer
+
+define void @dep_constraint_crash_test(i32 %k, i32 %N) {
+entry:
+  %cmp12 = icmp sgt i32 %N, 0
+  br i1 %cmp12, label %for.cond1.preheader.lr.ph, label %for.end6
+
+for.cond1.preheader.lr.ph:                        
+  %idxprom = sext i32 %k to i64
+  %arrayidx = getelementptr inbounds %struct.s, %struct.s* @S, i64 0, i32 1, i64 0, i64 0, i64 %idxprom
+  br label %for.body3.preheader
+
+for.body3.preheader:                              
+  %i.013 = phi i32 [ 0, %for.cond1.preheader.lr.ph ], [ %inc5, %for.inc4 ]
+  br label %for.body3
+
+for.body3:                                        
+  %j.011 = phi i32 [ %inc, %for.body3 ], [ 0, %for.body3.preheader ]
+  %0 = load i32, i32* %arrayidx
+  store i32 %0, i32* getelementptr inbounds (%struct.s* @S, i64 0, i32 0, i64 0, i64 0)
+  %inc = add nuw nsw i32 %j.011, 1
+  %exitcond = icmp eq i32 %inc, %N
+  br i1 %exitcond, label %for.inc4, label %for.body3
+
+for.inc4:                                         
+  %inc5 = add nuw nsw i32 %i.013, 1
+  %exitcond14 = icmp eq i32 %inc5, %N
+  br i1 %exitcond14, label %for.end6, label %for.body3.preheader
+
+for.end6:                                         
+  ret void
+}