1 files changed, 64 insertions, 0 deletions
diff --git a/llvm/test/Analysis/LoopAccessAnalysis/forward-loop-independent.ll b/llvm/test/Analysis/LoopAccessAnalysis/forward-loop-independent.ll
new file mode 100644
index 00000000000..c5573aee579
--- /dev/null
+++ b/llvm/test/Analysis/LoopAccessAnalysis/forward-loop-independent.ll
@@ -0,0 +1,64 @@
+; RUN: opt -loop-accesses -analyze < %s | FileCheck %s
+
+; Check that loop-indepedent forward dependences are discovered properly.
+;
+; FIXME: This does not actually always work which is pretty confusing.  Right
+; now there is hack in LAA that tries to figure out loop-indepedent forward
+; dependeces *outside* of the MemoryDepChecker logic (i.e. proper dependence
+; analysis).
+;
+; Therefore if there is only loop-independent dependences for an array
+; (i.e. the same index is used), we don't discover the forward dependence.
+; So, at ***, we add another non-I-based access of A to trigger
+; MemoryDepChecker analysis for accesses of A.
+;
+;   for (unsigned i = 0; i < 100; i++) {
+;     A[i + 1] = B[i] + 1;   // ***
+;     A[i] = B[i] + 2;
+;     C[i] = A[i] * 2;
+;   }
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @f(i32* noalias %A, i32* noalias %B, i32* noalias %C, i64 %N) {
+
+; CHECK: Interesting Dependences:
+; CHECK-NEXT:   Forward:
+; CHECK-NEXT:       store i32 %b_p1, i32* %Aidx, align 4 ->
+; CHECK-NEXT:       %a = load i32, i32* %Aidx, align 4
+; CHECK:        ForwardButPreventsForwarding:
+; CHECK-NEXT:       store i32 %b_p2, i32* %Aidx_next, align 4 ->
+; CHECK-NEXT:       %a = load i32, i32* %Aidx, align 4
+; CHECK:        Forward:
+; CHECK-NEXT:       store i32 %b_p2, i32* %Aidx_next, align 4 ->
+; CHECK-NEXT:       store i32 %b_p1, i32* %Aidx, align 4
+
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+
+  %Bidx = getelementptr inbounds i32, i32* %B, i64 %indvars.iv
+  %Cidx = getelementptr inbounds i32, i32* %C, i64 %indvars.iv
+  %Aidx_next = getelementptr inbounds i32, i32* %A, i64 %indvars.iv.next
+  %Aidx = getelementptr inbounds i32, i32* %A, i64 %indvars.iv
+
+  %b = load i32, i32* %Bidx, align 4
+  %b_p2 = add i32 %b, 1
+  store i32 %b_p2, i32* %Aidx_next, align 4
+
+  %b_p1 = add i32 %b, 2
+  store i32 %b_p1, i32* %Aidx, align 4
+
+  %a = load i32, i32* %Aidx, align 4
+  %c = mul i32 %a, 2
+  store i32 %c, i32* %Cidx, align 4
+
+  %exitcond = icmp eq i64 %indvars.iv.next, %N
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body
+  ret void
+}