[WebAssembly] Always print loop end labels

WebAssembly is currently using labels to end scopes, so for example a
loop scope looks like this:

BB0_0:
  loop BB0_1
  ...
BB0_1:

with BB0_0 being the label of the first block not in the loop. This
requires that the label be printed even when it's only reachable via
fallthrough. To arrange this, insert a no-op LOOP_END instruction in
such cases at the end of the loop.

llvm-svn: 253901

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
index c452e1dd024..f7f37ee8c89 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
@@ -221,6 +221,10 @@ void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
     // These represent values which are live into the function entry, so there's
     // no instruction to emit.
     break;
+  case WebAssembly::LOOP_END:
+    // This is a no-op which just exists to tell AsmPrinter.cpp that there's a
+    // fallthrough which nevertheless requires a label for the destination here.
+    break;
   default: {
     WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
     MCInst TmpInst;