[WebAssembly] Ignore DBG_VALUE in WebAssemblyCFGStackify pass when looking for block start

Summary:
Fixes https://bugs.llvm.org/show_bug.cgi?id=39158 and regression caused by
D49034. Though it is possible the problem was existed before and was exposed by
additional DBG_VALUEs.

Reviewers: sunfish, dschuff, aheejin

Reviewed By: aheejin

Subscribers: sbc100, aheejin, llvm-commits, alexcrichton, jgravelle-google

Differential Revision: https://reviews.llvm.org/D52837

llvm-svn: 343827

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
index e62b8b60d0d..93ca670bbdb 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
@@ -309,6 +309,8 @@ void WebAssemblyCFGStackify::placeBlockMarker(MachineBasicBlock &MBB) {
   // Local expression tree should go after the BLOCK.
   for (auto I = Header->getFirstTerminator(), E = Header->begin(); I != E;
        --I) {
+    if (std::prev(I)->isDebugInstr() || std::prev(I)->isPosition())
+      continue;
     if (WebAssembly::isChild(*std::prev(I), MFI))
       AfterSet.insert(&*std::prev(I));
     else
@@ -531,6 +533,8 @@ void WebAssemblyCFGStackify::placeTryMarker(MachineBasicBlock &MBB) {
   // Local expression tree should go after the TRY.
   for (auto I = Header->getFirstTerminator(), E = Header->begin(); I != E;
        --I) {
+    if (std::prev(I)->isDebugInstr() || std::prev(I)->isPosition())
+      continue;
     if (WebAssembly::isChild(*std::prev(I), MFI))
       AfterSet.insert(&*std::prev(I));
     else