[WebAssembly] Fix the CFG Stackifier to handle unoptimized branches

If a branch both branches to and falls through to the same block, treat it as
an explicit branch.

llvm-svn: 255803

1 files changed, 46 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/WebAssembly/cfg-stackify.ll b/llvm/test/CodeGen/WebAssembly/cfg-stackify.ll
index 7717f35fec0..a10fb614909 100644
--- a/llvm/test/CodeGen/WebAssembly/cfg-stackify.ll
+++ b/llvm/test/CodeGen/WebAssembly/cfg-stackify.ll
@@ -1054,3 +1054,49 @@ bb4:
 bb7:
   ret void
 }
+
+; A block can be "branched to" from another even if it is also reachable via
+; fallthrough from the other. This would normally be optimized away, so use
+; optnone to disable optimizations to test this case.
+
+; CHECK-LABEL: test13:
+; CHECK-NEXT:  .local i32{{$}}
+; CHECK:       block BB22_2{{$}}
+; CHECK:       br_if $pop4, BB22_2{{$}}
+; CHECK-NEXT:  return{{$}}
+; CHECK-NEXT:  BB22_2:
+; CHECK:       block BB22_4{{$}}
+; CHECK-NEXT:  br_if $0, BB22_4{{$}}
+; CHECK:       BB22_4:
+; CHECK:       block BB22_5{{$}}
+; CHECK:       br_if $pop6, BB22_5{{$}}
+; CHECK-NEXT:  BB22_5:
+; CHECK-NEXT:  unreachable{{$}}
+; OPT-LABEL: test13:
+; OPT-NEXT:  .local i32{{$}}
+; OPT:       block BB22_2{{$}}
+; OPT:       br_if $pop4, BB22_2{{$}}
+; OPT-NEXT:  return{{$}}
+; OPT-NEXT:  BB22_2:
+; OPT:       block BB22_4{{$}}
+; OPT-NEXT:  br_if $0, BB22_4{{$}}
+; OPT:       BB22_4:
+; OPT:       block BB22_5{{$}}
+; OPT:       br_if $pop6, BB22_5{{$}}
+; OPT-NEXT:  BB22_5:
+; OPT-NEXT:  unreachable{{$}}
+define void @test13() noinline optnone {
+bb:
+  br i1 undef, label %bb5, label %bb2
+bb1:
+  unreachable
+bb2:
+  br i1 undef, label %bb3, label %bb4
+bb3:
+  br label %bb4
+bb4:
+  %tmp = phi i1 [ false, %bb2 ], [ false, %bb3 ]
+  br i1 %tmp, label %bb1, label %bb1
+bb5:
+  ret void
+}