Fix a bug in SCEV's poison value propagation

The worklist algorithm introduced in rL271151 didn't check to see if the
direct users of the post-inc add recurrence propagates poison.  This
change fixes the problem and makes the code structure more obvious.

Note for release managers: correctness wise, this bug wasn't a
regression introduced by rL271151 -- the behavior of SCEV around
post-inc add recurrences was strictly improved (in terms of correctness)
in rL271151.

llvm-svn: 272179

1 files changed, 36 insertions, 0 deletions

diff --git a/llvm/test/Analysis/ScalarEvolution/nsw.ll b/llvm/test/Analysis/ScalarEvolution/nsw.ll
index d015717e354..e89973be2b0 100644
--- a/llvm/test/Analysis/ScalarEvolution/nsw.ll
+++ b/llvm/test/Analysis/ScalarEvolution/nsw.ll
@@ -204,3 +204,39 @@ for.body:
 for.end:
   ret void
 }
+
+
+define void @bad_postinc_nsw_a(i32 %n) {
+; CHECK-LABEL: Classifying expressions for: @bad_postinc_nsw_a
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i32 [ 0, %entry ], [ %iv.inc, %loop ]
+  %iv.inc = add nsw i32 %iv, 7
+; CHECK:    %iv.inc = add nsw i32 %iv, 7
+; CHECK-NEXT:  -->  {7,+,7}<nuw><%loop>
+  %becond = icmp ult i32 %iv, %n
+  br i1 %becond, label %loop, label %leave
+
+leave:
+  ret void
+}
+
+define void @bad_postinc_nsw_b(i32 %n) {
+; CHECK-LABEL: Classifying expressions for: @bad_postinc_nsw_b
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i32 [ 0, %entry ], [ %iv.inc, %loop ]
+  %iv.inc = add nsw i32 %iv, 7
+  %iv.inc.and = and i32 %iv.inc, 0
+; CHECK:    %iv.inc = add nsw i32 %iv, 7
+; CHECK-NEXT:  -->  {7,+,7}<nuw><%loop>
+  %becond = icmp ult i32 %iv.inc.and, %n
+  br i1 %becond, label %loop, label %leave
+
+leave:
+  ret void
+}