[Bitcode] Address backwards compat bug in r342631

r342631 expanded bitc::METADATA_LOCATION by one element. The bitcode
metadata loader was changed in a backwards-incompatible way, leading to
crashes when disassembling old bitcode:

  assertion: empty() && "PlaceholderQueue hasn't been flushed before being destroyed"
  Assertion failed: (empty() && "PlaceholderQueue hasn't been flushed before being destroyed")

This commit teaches the metadata loader to assume that the newly-added
IsImplicitCode bit is 'false' when not present in old bitcode. I've added a
bitcode compat regression test.

rdar://44645820

llvm-svn: 342678

2 files changed, 8 insertions, 0 deletions

diff --git a/llvm/test/Bitcode/Inputs/apple-clang-700-O3-g-1.bc b/llvm/test/Bitcode/Inputs/apple-clang-700-O3-g-1.bc
new file mode 100644
index 00000000000..01f221d575c
--- /dev/null
+++ b/llvm/test/Bitcode/Inputs/apple-clang-700-O3-g-1.bc
diff --git a/llvm/test/Bitcode/apple-clang-700-compat.test b/llvm/test/Bitcode/apple-clang-700-compat.test
new file mode 100644
index 00000000000..c7ab2f49687
--- /dev/null
+++ b/llvm/test/Bitcode/apple-clang-700-compat.test
@@ -0,0 +1,8 @@
+; AppleClang-700 uses a debug info version that isn't recognized by llvm.org
+; compilers. However, it does produce valid bitcode which should parse without
+; crashing the metadata loader.
+
+RUN: llvm-dis < %S/Inputs/apple-clang-700-O3-g-1.bc 2>&1 \
+RUN:   | FileCheck %s -check-prefix INVALID-VERSION
+
+INVALID-VERSION: warning: ignoring debug info with an invalid version (700000003)