[NFC][SimplifyCFG] FoldBranchToCommonDest: add one more test with PHI

This is the problematic pattern i didn't think of,
that lead to revert of 2245fb8aaa1c1f85f53f7b19a1ee3ac69b1a1dfe
in f3abd54958ab90ba7c100d3fa936a3ce0dd2ad04.

diff --git a/llvm/test/Transforms/SimplifyCFG/fold-branch-to-common-dest.ll b/llvm/test/Transforms/SimplifyCFG/fold-branch-to-common-dest.ll
index 1a6f795..6f83a20 100644 (file)
--- a/llvm/test/Transforms/SimplifyCFG/fold-branch-to-common-dest.ll
+++ b/llvm/test/Transforms/SimplifyCFG/fold-branch-to-common-dest.ll
@@ -3,6 +3,7 @@
 
 declare void @sideeffect0()
 declare void @sideeffect1()
+declare void @sideeffect2()
 declare void @use8(i8)
 
 ; Basic cases, blocks have nothing other than the comparison itself.
@@ -304,6 +305,55 @@ final_right:
   ret void
 }
 
+define void @one_pred_with_extra_op_liveout_distant_phi(i8 %v0, i8 %v1) {
+; CHECK-LABEL: @one_pred_with_extra_op_liveout_distant_phi(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[C0:%.*]] = icmp eq i8 [[V0:%.*]], 0
+; CHECK-NEXT:    br i1 [[C0]], label [[PRED:%.*]], label [[LEFT_END:%.*]]
+; CHECK:       pred:
+; CHECK-NEXT:    [[C1:%.*]] = icmp eq i8 [[V1:%.*]], 0
+; CHECK-NEXT:    br i1 [[C1]], label [[DISPATCH:%.*]], label [[FINAL_RIGHT:%.*]]
+; CHECK:       dispatch:
+; CHECK-NEXT:    [[V2_ADJ:%.*]] = add i8 [[V0]], [[V1]]
+; CHECK-NEXT:    [[C2:%.*]] = icmp eq i8 [[V2_ADJ]], 0
+; CHECK-NEXT:    br i1 [[C2]], label [[FINAL_LEFT:%.*]], label [[FINAL_RIGHT]]
+; CHECK:       final_left:
+; CHECK-NEXT:    call void @sideeffect0()
+; CHECK-NEXT:    call void @use8(i8 [[V2_ADJ]])
+; CHECK-NEXT:    br label [[LEFT_END]]
+; CHECK:       left_end:
+; CHECK-NEXT:    [[MERGE_LEFT:%.*]] = phi i8 [ [[V2_ADJ]], [[FINAL_LEFT]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    call void @sideeffect1()
+; CHECK-NEXT:    call void @use8(i8 [[MERGE_LEFT]])
+; CHECK-NEXT:    ret void
+; CHECK:       final_right:
+; CHECK-NEXT:    call void @sideeffect2()
+; CHECK-NEXT:    ret void
+;
+entry:
+  %c0 = icmp eq i8 %v0, 0
+  br i1 %c0, label %pred, label %left_end
+pred:
+  %c1 = icmp eq i8 %v1, 0
+  br i1 %c1, label %dispatch, label %final_right
+dispatch:
+  %v2_adj = add i8 %v0, %v1
+  %c2 = icmp eq i8 %v2_adj, 0
+  br i1 %c2, label %final_left, label %final_right
+final_left:
+  call void @sideeffect0()
+  call void @use8(i8 %v2_adj)
+  br label %left_end
+left_end:
+  %merge_left = phi i8 [ %v2_adj, %final_left ], [ 0, %entry ]
+  call void @sideeffect1()
+  call void @use8(i8 %merge_left)
+  ret void
+final_right:
+  call void @sideeffect2()
+  ret void
+}
+
 define void @two_preds_with_extra_op_liveout(i8 %v0, i8 %v1, i8 %v2, i8 %v3) {
 ; CHECK-LABEL: @two_preds_with_extra_op_liveout(
 ; CHECK-NEXT:  entry: