[WebAssembly] Fix bugs in rethrow depth counting and InstPrinter

Summary:
EH stack depth is incremented at `try` and decremented at `catch`. When
there are more than two catch instructions for a try instruction, we
shouldn't count non-first catches when calculating EH stack depths.

This patch fixes two bugs:
- CFGStackify: Exclude `catch_all` in the terminate catch pad when
  calculating EH pad stack, because when we have multiple catches for a
  try we should count only the first catch instruction when calculating
  EH pad stack.
- InstPrinter: The initial intention was also to exclude non-first
  catches, but it didn't account nested try-catches, so it failed on
  this case:
```
try
  try
  catch
  end
catch    <-- (1)
end
```
In the example, when we are at the catch (1), the last seen EH
instruction is not `try` but `end_try`, violating the wrong assumption.

We don't need these after we switch to the second proposal because there
is gonna be only one `catch` instruction. But anyway before then these
bugfixes are necessary for keep trunk in working state.

Reviewers: dschuff

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

Differential Revision: https://reviews.llvm.org/D53819

llvm-svn: 346029

1 files changed, 2 insertions, 3 deletions

diff --git a/llvm/lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.cpp b/llvm/lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.cpp
index 6b97e14364f..e94faa1a214 100644
--- a/llvm/lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.cpp
+++ b/llvm/lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.cpp
@@ -120,10 +120,9 @@ void WebAssemblyInstPrinter::printInst(const MCInst *MI, raw_ostream &OS,
     case WebAssembly::CATCH_I64_S:
     case WebAssembly::CATCH_ALL:
     case WebAssembly::CATCH_ALL_S:
-      assert(LastSeenEHInst != END_TRY);
       // There can be multiple catch instructions for one try instruction, so we
-      // only print 'catch' label when the last seen EH instruction was 'try'.
-      if (LastSeenEHInst == TRY) {
+      // print a label only for the first 'catch' label.
+      if (LastSeenEHInst != CATCH) {
         assert(!EHPadStack.empty() && "try-catch mismatch!");
         printAnnotation(OS, "catch" + utostr(EHPadStack.pop_back_val()) + ':');
       }