Fix LoopSimplify to notify ScalarEvolution when splitting a loop backedge

into an inner loop, as the new loop iteration may differ substantially.
This fixes PR8078.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113057 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 50 insertions, 0 deletions

diff --git a/test/Transforms/LoopSimplify/preserve-scev.ll b/test/Transforms/LoopSimplify/preserve-scev.ll
new file mode 100644
index 0000000000..017a0d2108
--- /dev/null
+++ b/test/Transforms/LoopSimplify/preserve-scev.ll
@@ -0,0 +1,50 @@
+; RUN: opt -S < %s -indvars | opt -analyze -iv-users | grep {%cmp = icmp slt i32} | grep {= \{%\\.ph,+,1\}<%for.cond>}
+; PR8079
+
+; LoopSimplify should invalidate indvars when splitting out the
+; inner loop.
+
+@maxStat = external global i32
+
+define i32 @test() nounwind {
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %if.then5, %if.end, %entry
+  %cuts.1 = phi i32 [ 0, %entry ], [ %inc, %if.then5 ], [ %cuts.1, %if.end ]
+  %0 = phi i32 [ 0, %entry ], [ %add, %if.end ], [ %add, %if.then5 ]
+  %add = add i32 %0, 1
+  %cmp = icmp slt i32 %0, 1
+  %tmp1 = load i32* @maxStat, align 4
+  br i1 %cmp, label %for.body, label %for.cond14.preheader
+
+for.cond14.preheader:                             ; preds = %for.cond
+  %cmp1726 = icmp sgt i32 %tmp1, 0
+  br i1 %cmp1726, label %for.body18, label %return
+
+for.body:                                         ; preds = %for.cond
+  %cmp2 = icmp sgt i32 %tmp1, 100
+  br i1 %cmp2, label %return, label %if.end
+
+if.end:                                           ; preds = %for.body
+  %cmp4 = icmp sgt i32 %tmp1, -1
+  br i1 %cmp4, label %if.then5, label %for.cond
+
+if.then5:                                         ; preds = %if.end
+  call void @foo() nounwind
+  %inc = add i32 %cuts.1, 1
+  br label %for.cond
+
+for.body18:                                       ; preds = %for.body18, %for.cond14.preheader
+  %i13.027 = phi i32 [ %1, %for.body18 ], [ 0, %for.cond14.preheader ]
+  call void @foo() nounwind
+  %1 = add nsw i32 %i13.027, 1
+  %tmp16 = load i32* @maxStat, align 4
+  %cmp17 = icmp slt i32 %1, %tmp16
+  br i1 %cmp17, label %for.body18, label %return
+
+return:                                           ; preds = %for.body18, %for.body, %for.cond14.preheader
+  ret i32 0
+}
+
+declare void @foo() nounwind