LoopVectorize: PHIs with only outside users should prevent vectorization

We check that instructions in the loop don't have outside users (except if
they are reduction values). Unfortunately, we skipped this check for
if-convertable PHIs.

Fixes PR16184.

llvm-svn: 183035

1 files changed, 41 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopVectorize/no_outside_user.ll b/llvm/test/Transforms/LoopVectorize/no_outside_user.ll
new file mode 100644
index 00000000000..6f0357c5e54
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/no_outside_user.ll
@@ -0,0 +1,41 @@
+; RUN: opt -S -loop-vectorize -force-vector-unroll=1 -force-vector-width=2 < %s | FileCheck %s
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32-S128"
+
+@f = common global i32 0, align 4
+@.str = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1
+@c = common global i32 0, align 4
+@a = common global i32 0, align 4
+@b = common global i32 0, align 4
+@e = common global i32 0, align 4
+
+; We used to vectorize this loop. But it has a value that is used outside of the
+; and is not a recognized reduction variable "tmp17".
+
+; CHECK-NOT: <2 x i32>
+
+define i32 @main()  {
+bb:
+  %b.promoted = load i32* @b, align 4
+  br label %.lr.ph.i
+
+.lr.ph.i:
+  %tmp8 = phi i32 [ %tmp18, %bb16 ], [ %b.promoted, %bb ]
+  %tmp2 = icmp sgt i32 %tmp8, 10
+  br i1 %tmp2, label %bb16, label %bb10
+
+bb10:
+  br label %bb16
+
+bb16:
+  %tmp17 = phi i32 [ 0, %bb10 ], [ 1, %.lr.ph.i ]
+  %tmp18 = add nsw i32 %tmp8, 1
+  %tmp19 = icmp slt i32 %tmp18, 4
+  br i1 %tmp19, label %.lr.ph.i, label %f1.exit.loopexit
+
+f1.exit.loopexit:
+  %.lcssa = phi i32 [ %tmp17, %bb16 ]
+  ret i32 %.lcssa
+}
+
+