[clang] ae6523c - [DebugInfo] Add -fuse-ctor-homing cc1 flag so we can turn on constructor homing only if limited debug info is already on.

[Amy Huang via cfe-commits]

Author: Amy Huang
Date: 2020-08-13T15:48:55-07:00
New Revision: ae6523cd62a44642390f4f9d9ba9ce17d5bbbc58

URL: https://github.com/llvm/llvm-project/commit/ae6523cd62a44642390f4f9d9ba9ce17d5bbbc58
DIFF: https://github.com/llvm/llvm-project/commit/ae6523cd62a44642390f4f9d9ba9ce17d5bbbc58.diff

LOG: [DebugInfo] Add -fuse-ctor-homing cc1 flag so we can turn on constructor homing only if limited debug info is already on.

This adds a cc1 flag to enable constructor homing but doesn't turn on debug
info if it wasn't enabled already (which is what using
-debug-info-kind=constructor does). This will be used for testing, and won't
be needed anymore once ctor homing is used as default / merged into =limited.

Bug to enable ctor homing: https://bugs.llvm.org/show_bug.cgi?id=46537

Differential Revision: https://reviews.llvm.org/D85799

Added: 
    clang/test/CodeGenCXX/debug-info-ctor-homing-flag.cpp

Modified: 
    clang/include/clang/Driver/Options.td
    clang/lib/Frontend/CompilerInvocation.cpp

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 99a2ec7ad2d4..9d36dc6cc393 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3691,6 +3691,8 @@ def mrelocation_model : Separate<["-"], "mrelocation-model">,
   AutoNormalizeEnum;
 def fno_math_builtin : Flag<["-"], "fno-math-builtin">,
   HelpText<"Disable implicit builtin knowledge of math functions">;
+def fuse_ctor_homing: Flag<["-"], "fuse-ctor-homing">,
+    HelpText<"Use constructor homing if we are using limited debug info already">;
 }
 
 def disable_llvm_verifier : Flag<["-"], "disable-llvm-verifier">,

diff  --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 17c43ec55c79..86504ed9f92b 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -775,6 +775,12 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
     else
       Opts.setDebugInfo(static_cast<codegenoptions::DebugInfoKind>(Val));
   }
+  // If -fuse-ctor-homing is set and limited debug info is already on, then use
+  // constructor homing.
+  if (Arg *A = Args.getLastArg(OPT_fuse_ctor_homing))
+    if (Opts.getDebugInfo() == codegenoptions::LimitedDebugInfo)
+      Opts.setDebugInfo(codegenoptions::DebugInfoConstructor);
+
   if (Arg *A = Args.getLastArg(OPT_debugger_tuning_EQ)) {
     unsigned Val = llvm::StringSwitch<unsigned>(A->getValue())
                        .Case("gdb", unsigned(llvm::DebuggerKind::GDB))

diff  --git a/clang/test/CodeGenCXX/debug-info-ctor-homing-flag.cpp b/clang/test/CodeGenCXX/debug-info-ctor-homing-flag.cpp
new file mode 100644
index 000000000000..5443fa9ade23
--- /dev/null
+++ b/clang/test/CodeGenCXX/debug-info-ctor-homing-flag.cpp
@@ -0,0 +1,20 @@
+// RUN: %clang -cc1 -debug-info-kind=constructor -emit-llvm %s -o - \
+// RUN:        | FileCheck %s -check-prefix=CTOR_HOMING
+// RUN: %clang -cc1 -debug-info-kind=limited -fuse-ctor-homing -emit-llvm %s -o - \
+// RUN:        | FileCheck %s -check-prefix=CTOR_HOMING
+// RUN: %clang -cc1 -debug-info-kind=standalone -fuse-ctor-homing -emit-llvm %s -o - \
+// RUN:        | FileCheck %s -check-prefix=FULL_DEBUG
+// RUN: %clang -cc1 -debug-info-kind=line-tables-only -fuse-ctor-homing -emit-llvm %s -o - \
+// RUN:        | FileCheck %s -check-prefix=NO_DEBUG
+// RUN: %clang -cc1 -fuse-ctor-homing -emit-llvm %s -o - \
+// RUN:        | FileCheck %s -check-prefix=NO_DEBUG
+
+// This tests that the -fuse-ctor-homing is only used if limited debug info would have
+// been used otherwise.
+
+// CTOR_HOMING: !DICompositeType(tag: DW_TAG_structure_type, name: "A"{{.*}}flags: DIFlagFwdDecl
+// FULL_DEBUG: !DICompositeType(tag: DW_TAG_structure_type, name: "A"{{.*}}DIFlagTypePassByValue
+// NO_DEBUG-NOT: !DICompositeType(tag: DW_TAG_structure_type, name: "A"
+struct A {
+  A();
+} TestA;