[WebAssembly] Handle END_LOOP in unreachable BB in CFGStackify
Summary:
This fixes crashes when a BB in which an END_LOOP is to be placed is
unreachable and does not have any predecessors. Fixes PR41307.
Reviewers: dschuff
Subscribers: yurydelendik, sbc100, jgravelle-google, sunfish, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60004
llvm-svn: 357303
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
index 39641b4..b64aa30 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
@@ -411,7 +411,9 @@
// Mark the end of the loop (using arbitrary debug location that branched to
// the loop end as its location).
InsertPos = getEarliestInsertPos(AfterLoop, BeforeSet, AfterSet);
- DebugLoc EndDL = (*AfterLoop->pred_rbegin())->findBranchDebugLoc();
+ DebugLoc EndDL = AfterLoop->pred_empty()
+ ? DebugLoc()
+ : (*AfterLoop->pred_rbegin())->findBranchDebugLoc();
MachineInstr *End =
BuildMI(*AfterLoop, InsertPos, EndDL, TII.get(WebAssembly::END_LOOP));
registerScope(Begin, End);
diff --git a/llvm/test/CodeGen/WebAssembly/cfg-stackify-dbg.mir b/llvm/test/CodeGen/WebAssembly/cfg-stackify-dbg.mir
new file mode 100644
index 0000000..cd76d91
--- /dev/null
+++ b/llvm/test/CodeGen/WebAssembly/cfg-stackify-dbg.mir
@@ -0,0 +1,27 @@
+# RUN: llc -mtriple=wasm32-unknown-unknown -run-pass wasm-cfg-stackify %s -o - | FileCheck %s
+
+# This tests if END_LOOP marker is placed correctly when the BB it is to be
+# placed is unreachable. Regression test for PR41307.
+
+# CHECK-LABEL: unreachable_test
+name: unreachable_test
+liveins:
+ - { reg: '$arguments' }
+body: |
+ bb.0:
+ successors: %bb.1
+
+ bb.1:
+ ; predecessors: %bb.0, %bb.2
+ successors: %bb.2
+
+ bb.2:
+ ; predecessors: %bb.1
+ successors: %bb.1
+ BR %bb.1, implicit-def dead $arguments
+
+ ; CHECK: bb.3
+ ; CHECK: END_LOOP
+ bb.3:
+ UNREACHABLE implicit-def $arguments
+...