[LoopInterchange] Skip dependence check to the same instruction

Author: ShivaChen

llvm/lib/Transforms/Scalar/LoopInterchange.cpp

@@ -113,7 +113,7 @@ static bool populateDependencyMatrix(CharMatrix &DepMatrix, unsigned Level,
   ValueVector::iterator I, IE, J, JE;
 
   for (I = MemInstr.begin(), IE = MemInstr.end(); I != IE; ++I) {
-    for (J = I, JE = MemInstr.end(); J != JE; ++J) {
+    for (J = I + 1, JE = MemInstr.end(); J != JE; ++J) {
       std::vector<char> Dep;
       Instruction *Src = cast<Instruction>(*I);
       Instruction *Dst = cast<Instruction>(*J);

llvm/test/Transforms/LoopInterchange/interchange-s231.ll

@@ -10,9 +10,9 @@
 ;;      for (int j = 1; j < 256; j++)
 ;;        aa[j][i] = aa[j - 1][i] + bb[j][i];
 
-; CHECK: Found output dependency between Src and Dst
-; CHECK:  Src:  store float %add, ptr %arrayidx18
-; CHECK:  Dst:  store float %add, ptr %arrayidx18
+; CHECK: Found anti dependency between Src and Dst
+; CHECK:  Src:  %1 = load float, ptr %arrayidx10, align 4
+; CHECK:  Dst:  store float %add, ptr %arrayidx18, align 4
 ; CHECK: Processing InnerLoopId = 2 and OuterLoopId = 1
 ; CHECK: Not interchanging loops. Cannot prove legality.