[WebAssembly] Error out when block/loop markers mismatch

Summary:
Currently InstPrinter ignores if there are mismatches between block/loop
and end markers by skipping the case if ControlFlowStack is empty. I
guess it is better to explicitly error out in this case, because this
signals invalid input.

Reviewers: aardappel

Subscribers: dschuff, sbc100, jgravelle-google, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D53620

llvm-svn: 345333

1 files changed, 7 insertions, 7 deletions

diff --git a/llvm/lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.cpp b/llvm/lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.cpp
index 08c1155fed7..e26cf1d8cf4 100644
--- a/llvm/lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.cpp
+++ b/llvm/lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.cpp
@@ -85,16 +85,16 @@ void WebAssemblyInstPrinter::printInst(const MCInst *MI, raw_ostream &OS,
       break;
     case WebAssembly::END_LOOP:
     case WebAssembly::END_LOOP_S:
-      // Have to guard against an empty stack, in case of mismatched pairs
-      // in assembly parsing.
-      if (!ControlFlowStack.empty())
-        ControlFlowStack.pop_back();
+      if (ControlFlowStack.empty())
+        report_fatal_error("End marker mismatch!");
+      ControlFlowStack.pop_back();
       break;
     case WebAssembly::END_BLOCK:
     case WebAssembly::END_BLOCK_S:
-      if (!ControlFlowStack.empty())
-        printAnnotation(
-            OS, "label" + utostr(ControlFlowStack.pop_back_val().first) + ':');
+      if (ControlFlowStack.empty())
+        report_fatal_error("END marker mismatch!");
+      printAnnotation(
+          OS, "label" + utostr(ControlFlowStack.pop_back_val().first) + ':');
       break;
     }