[LowerSwitch] Fixed faulty PHI node update

Summary:
When lowerswitch merge several cases into a new default block it's not
updating the PHI nodes accordingly. The code that update the PHI nodes
for the default edge only update the first entry and do not remove the
remaining ones, to make sure the number of entries match the number of
predecessors.

This is easily fixed by replacing the code that update the PHI node with
the already existing utility function for updating PHI nodes.

Reviewers: hans, reames, arsenm

Reviewed By: arsenm

Subscribers: wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D47055

llvm-svn: 332960

1 files changed, 57 insertions, 1 deletions

diff --git a/llvm/test/Transforms/Util/lowerswitch.ll b/llvm/test/Transforms/Util/lowerswitch.ll
index 1eddb43c1a0..70e1e239b3d 100644
--- a/llvm/test/Transforms/Util/lowerswitch.ll
+++ b/llvm/test/Transforms/Util/lowerswitch.ll
@@ -3,7 +3,7 @@
 ; Test that we don't crash and have a different basic block for each incoming edge.
 define void @test0() {
 ; CHECK-LABEL: @test0
-; CHECK: %merge = phi i64 [ 1, %BB3 ], [ 0, %NewDefault ], [ 0, %NodeBlock5 ], [ 0, %LeafBlock1 ]
+; CHECK: %merge = phi i64 [ 1, %BB3 ], [ 0, %NodeBlock5 ], [ 0, %LeafBlock1 ], [ 0, %NewDefault ]
 BB1:
   switch i32 undef, label %BB2 [
     i32 3, label %BB2
@@ -186,3 +186,59 @@ define void @test2(i32 %mode) {
 ._crit_edge:                                      ; preds = %34, %0
   ret void
 }
+
+; Test that the PHI node in for.cond should have one entry for each predecessor
+; of its parent basic block after lowerswitch merged several cases into a new
+; default block.
+define void @test3() {
+; CHECK-LABEL: @test3
+entry:
+  br label %lbl1
+
+lbl1:                                             ; preds = %cleanup, %entry
+  br label %lbl2
+
+lbl2:                                             ; preds = %cleanup, %lbl1
+  br label %for.cond
+
+for.cond:                                         ; preds = %cleanup, %cleanup, %lbl2
+; CHECK: for.cond:
+; CHECK: phi i16 [ undef, %lbl2 ], [ %b.3, %NewDefault ]{{$}}
+; CHECK: for.cond1:
+  %b.2 = phi i16 [ undef, %lbl2 ], [ %b.3, %cleanup ], [ %b.3, %cleanup ]
+  br label %for.cond1
+
+for.cond1:                                        ; preds = %for.inc, %for.cond
+  %b.3 = phi i16 [ %b.2, %for.cond ], [ undef, %for.inc ]
+  %tobool = icmp ne i16 %b.3, 0
+  br i1 %tobool, label %for.body, label %for.end
+
+for.body:                                         ; preds = %for.cond1
+  br i1 undef, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  br label %cleanup
+
+for.inc:                                          ; preds = %for.body
+  br label %for.cond1
+
+for.end:                                          ; preds = %for.cond1
+  br i1 undef, label %if.then4, label %for.body7
+
+if.then4:                                         ; preds = %for.end
+  br label %cleanup
+
+for.body7:                                        ; preds = %for.end
+  br label %cleanup
+
+cleanup:                                          ; preds = %for.body7, %if.then4, %if.then
+  switch i32 undef, label %unreachable [
+    i32 0, label %for.cond
+    i32 2, label %lbl1
+    i32 5, label %for.cond
+    i32 3, label %lbl2
+  ]
+
+unreachable:                                      ; preds = %cleanup
+  unreachable
+}