Suppress the IV reversal transformation in the case that the RHS

of the comparison is defined inside the loop. This fixes a
use-before-def problem, because the transformation puts a use
of the RHS outside the loop.

llvm-svn: 72149

1 files changed, 21 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopStrengthReduce/dont_reverse.ll b/llvm/test/Transforms/LoopStrengthReduce/dont_reverse.ll
new file mode 100644
index 00000000000..39eca6c9630
--- /dev/null
+++ b/llvm/test/Transforms/LoopStrengthReduce/dont_reverse.ll
@@ -0,0 +1,21 @@
+; RUN: llvm-as < %s | opt -loop-reduce | llvm-dis \
+; RUN:    | grep {icmp eq i2 %lsr.iv.next, %xmp4344}
+
+; Don't reverse the iteration if the rhs of the compare is defined
+; inside the loop.
+
+define void @Fill_Buffer() nounwind {
+entry:
+	br label %bb8
+
+bb8:
+	%indvar34 = phi i32 [ 0, %entry ], [ %indvar.next35, %bb8 ]
+	%indvar3451 = trunc i32 %indvar34 to i2
+	%xmp4344 = xor i2 0, -1
+	%xmp104 = icmp eq i2 %indvar3451, %xmp4344
+	%indvar.next35 = add i32 %indvar34, 1
+	br i1 %xmp104, label %bb10, label %bb8
+
+bb10:
+	unreachable
+}