[LoopUnswitch] Fix SCEV invalidation in unswitching

Loop unswitching makes substantial changes to a loop that can also affect cached
SCEV info in its outer loops as well, but it only cares to invalidate SCEV cache for the
innermost loop in case of full unswitching and does not invalidate anything at all in
case of trivial unswitching. As result, we may end up with incorrect data in cache.

Differential Revision: https://reviews.llvm.org/D46045
Reviewed By: mzolotukhin

llvm-svn: 333072

1 files changed, 33 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopUnswitch/invalidate-scev.ll b/llvm/test/Transforms/LoopUnswitch/invalidate-scev.ll
new file mode 100644
index 00000000000..f1e9443556a
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnswitch/invalidate-scev.ll
@@ -0,0 +1,33 @@
+; RUN: opt -S -indvars -loop-unswitch < %s | FileCheck %s
+
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @test_01() {
+
+; Make sure we don't fail by SCEV's assertion due to incorrect invalidation.
+; CHECK-LABEL: @test_01
+
+entry:
+  br label %loop
+
+loop:                           ; preds = %backedge, %entry
+  %p_50.addr.0 = phi i16 [ undef, %entry ], [ %add2699, %backedge ]
+  %idxprom2690 = sext i16 %p_50.addr.0 to i32
+  %arrayidx2691 = getelementptr inbounds [5 x i32], [5 x i32]* undef, i32 0, i32 %idxprom2690
+  %0 = load i32, i32* %arrayidx2691, align 1
+  %tobool2692 = icmp ne i32 %0, 0
+  br label %inner_loop
+
+inner_loop:                                     ; preds = %inner_backedge, %loop
+  br i1 %tobool2692, label %backedge, label %inner_backedge
+
+inner_backedge:                                       ; preds = %inner_loop
+  br label %inner_loop
+
+backedge:                                      ; preds = %inner_loop
+  %add2699 = add nsw i16 %p_50.addr.0, 1
+  br i1 false, label %loop, label %exit
+
+exit:               ; preds = %backedge
+  unreachable
+}