[DebugInfo] LowerDbgDeclare: Add derefs when handling CallInst users

LowerDbgDeclare inserts a dbg.value before each use of an address
described by a dbg.declare. When inserting a dbg.value before a CallInst
use, however, it fails to append DW_OP_deref to the DIExpression.

The DW_OP_deref is needed to reflect the fact that a dbg.value describes
a source variable directly (as opposed to a dbg.declare, which relies on
pointer indirection).

This patch adds in the DW_OP_deref where needed. This results in the
correct values being shown during a debug session for a program compiled
with ASan and optimizations (see https://reviews.llvm.org/D49520). Note
that ConvertDebugDeclareToDebugValue is already correct -- no changes
there were needed.

One complication is that SelectionDAG is unable to distinguish between
direct and indirect frame-index (FRAMEIX) SDDbgValues. This patch also
fixes this long-standing issue in order to not regress integration tests
relying on the incorrect assumption that all frame-index SDDbgValues are
indirect. This is a necessary fix: the newly-added DW_OP_derefs cannot
be lowered properly otherwise. Basically the fix prevents a direct
SDDbgValue with DIExpression(DW_OP_deref) from being dereferenced twice
by a debugger. There were a handful of tests relying on this incorrect
"FRAMEIX => indirect" assumption which actually had incorrect
DW_AT_locations: these are all fixed up in this patch.

Testing:

- check-llvm, and an end-to-end test using lldb to debug an optimized
  program.
- Existing unit tests for DIExpression::appendToStack fully cover the
  new DIExpression::append utility.
- check-debuginfo (the debug info integration tests)

Differential Revision: https://reviews.llvm.org/D49454

llvm-svn: 338069

1 files changed, 46 insertions, 0 deletions

diff --git a/debuginfo-tests/asan-deque.cpp b/debuginfo-tests/asan-deque.cpp
new file mode 100644
index 00000000000..19183d6cc15
--- /dev/null
+++ b/debuginfo-tests/asan-deque.cpp
@@ -0,0 +1,46 @@
+// RUN: %clangxx -arch x86_64 %target_itanium_abi_host_triple -O1 -g %s -o %t.out -fsanitize=address
+// RUN: %test_debuginfo %s %t.out
+// REQUIRES: not_asan
+//           Zorg configures the ASAN stage2 bots to not build the asan
+//           compiler-rt. Only run this test on non-asanified configurations.
+
+#include <deque>
+
+struct A {
+  int a;
+  A(int a) : a(a) {}
+};
+
+using log_t = std::deque<A>;
+
+static void __attribute__((noinline, optnone)) escape(log_t &log) {
+  static volatile log_t *sink;
+  sink = &log;
+}
+
+int main() {
+  log_t log;
+  log.emplace_back(1234);
+  log.emplace_back(56789);
+  escape(log);
+  // DEBUGGER: break 25
+  while (!log.empty()) {
+    auto record = log.front();
+    log.pop_front();
+    escape(log);
+    // DEBUGGER: break 30
+  }
+}
+
+// DEBUGGER: r
+
+// (at line 25)
+// DEBUGGER: p log
+// CHECK: 1234
+// CHECK: 56789
+
+// DEBUGGER: c
+
+// (at line 30)
+// DEBUGGER: p log
+// CHECK: 56789