Implement -Wframe-larger-than backend diagnostic

Add driver and frontend support for the GCC -Wframe-larger-than=bytes warning.
This is the first GCC-compatible backend diagnostic built around LLVM's
reporting feature.

This commit adds infrastructure to perform reverse lookup from mangled names
emitted after LLVM IR generation. We use that to resolve precise locations and
originating AST functions, lambdas or block declarations to produce seamless
codegen-guided diagnostics.

An associated change, StringMap now maintains unique mangled name strings
instead of allocating copies. This is a net memory saving in C++ and a small
hit for C where we no longer reuse IdentifierInfo storage, pending further
optimisation.

llvm-svn: 210293

2 files changed, 69 insertions, 0 deletions

diff --git a/clang/test/Misc/backend-stack-frame-diagnostics-fallback.cpp b/clang/test/Misc/backend-stack-frame-diagnostics-fallback.cpp
new file mode 100644
index 00000000000..8ae8c55396d
--- /dev/null
+++ b/clang/test/Misc/backend-stack-frame-diagnostics-fallback.cpp
@@ -0,0 +1,18 @@
+// REQUIRES: x86-registered-target
+// RUN: %clang_cc1 %s -mllvm -warn-stack-size=0 -emit-codegen-only -triple=i386-apple-darwin 2>&1 | FileCheck %s
+
+// TODO: Emit rich diagnostics for thunks and move this into the appropriate test file.
+// Until then, test that we fall back and display the LLVM backend diagnostic.
+namespace frameSizeThunkWarning {
+  struct A {
+    virtual void f();
+  };
+
+  struct B : virtual A {
+    virtual void f();
+  };
+
+  // CHECK: warning: stack frame size of {{[0-9]+}} bytes in function 'frameSizeThunkWarning::B::f'
+  // CHECK: warning: stack size limit exceeded ({{[0-9]+}}) in {{[^ ]+}}
+  void B::f() { }
+}
diff --git a/clang/test/Misc/backend-stack-frame-diagnostics.cpp b/clang/test/Misc/backend-stack-frame-diagnostics.cpp
new file mode 100644
index 00000000000..19303594b2b
--- /dev/null
+++ b/clang/test/Misc/backend-stack-frame-diagnostics.cpp
@@ -0,0 +1,51 @@
+// REQUIRES: x86-registered-target
+// RUN: %clang -target i386-apple-darwin -std=c++11 -fblocks -Wframe-larger-than=70 -Xclang -verify -o /dev/null -c %s
+
+// Test that:
+//  * The driver passes the option through to the backend.
+//  * The frontend diagnostic handler 'demangles' and resolves the correct function definition.
+
+// TODO: Support rich backend diagnostics for Objective-C methods.
+
+extern void doIt(char *);
+
+void frameSizeWarning(int, int) {}
+
+void frameSizeWarning();
+
+void frameSizeWarning() { // expected-warning-re {{stack frame size of {{[0-9]+}} bytes in function 'frameSizeWarning'}}
+  char buffer[80];
+  doIt(buffer);
+}
+
+void frameSizeWarning();
+
+void frameSizeWarning(int) {}
+
+void frameSizeLocalClassWarning() {
+  struct S {
+    S() { // expected-warning-re {{stack frame size of {{[0-9]+}} bytes in function 'frameSizeLocalClassWarning()::S::S'}}
+      char buffer[80];
+      doIt(buffer);
+    }
+  };
+  S();
+}
+
+void frameSizeLambdaWarning() {
+  auto fn =
+      []() { // expected-warning-re {{stack frame size of {{[0-9]+}} bytes in lambda expression}}
+    char buffer[80];
+    doIt(buffer);
+  };
+  fn();
+}
+
+void frameSizeBlocksWarning() {
+  auto fn =
+      ^() { // expected-warning-re {{stack frame size of {{[0-9]+}} bytes in block literal}}
+    char buffer[80];
+    doIt(buffer);
+  };
+  fn();
+}