ARM-Darwin: ignore and diagnose attempts to omit frame pointer.

iOS (and other 32-bit ARM variants) always require a valid frame pointer to
improve backtraces. Previously the -fomit-frame-pointer and
-momit-leaf-frame-pointer options were being silently discarded via hacks in
the backend. It's better if Clang configures itself to emit the correct IR and
warns about (ignored) attempts to override this.

llvm-svn: 279546

1 files changed, 22 insertions, 6 deletions

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 747f3ea57a1..895104e1c45 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -3232,8 +3232,20 @@ static bool areOptimizationsEnabled(const ArgList &Args) {
   return false;
 }
 
-static bool shouldUseFramePointerForTarget(const ArgList &Args,
-                                           const llvm::Triple &Triple) {
+static bool mustUseFramePointerForTarget(const llvm::Triple &Triple) {
+  switch (Triple.getArch()){
+  default:
+    return false;
+  case llvm::Triple::arm:
+  case llvm::Triple::thumb:
+    // ARM Darwin targets require a frame pointer to be always present to aid
+    // offline debugging via backtraces.
+    return Triple.isOSDarwin();
+  }
+}
+
+static bool useFramePointerForTargetByDefault(const ArgList &Args,
+                                              const llvm::Triple &Triple) {
   switch (Triple.getArch()) {
   case llvm::Triple::xcore:
   case llvm::Triple::wasm32:
@@ -3285,25 +3297,29 @@ static bool shouldUseFramePointer(const ArgList &Args,
                                   const llvm::Triple &Triple) {
   if (Arg *A = Args.getLastArg(options::OPT_fno_omit_frame_pointer,
                                options::OPT_fomit_frame_pointer))
-    return A->getOption().matches(options::OPT_fno_omit_frame_pointer);
+    return A->getOption().matches(options::OPT_fno_omit_frame_pointer) ||
+           mustUseFramePointerForTarget(Triple);
+
   if (Args.hasArg(options::OPT_pg))
     return true;
 
-  return shouldUseFramePointerForTarget(Args, Triple);
+  return useFramePointerForTargetByDefault(Args, Triple);
 }
 
 static bool shouldUseLeafFramePointer(const ArgList &Args,
                                       const llvm::Triple &Triple) {
   if (Arg *A = Args.getLastArg(options::OPT_mno_omit_leaf_frame_pointer,
                                options::OPT_momit_leaf_frame_pointer))
-    return A->getOption().matches(options::OPT_mno_omit_leaf_frame_pointer);
+    return A->getOption().matches(options::OPT_mno_omit_leaf_frame_pointer) ||
+           mustUseFramePointerForTarget(Triple);
+
   if (Args.hasArg(options::OPT_pg))
     return true;
 
   if (Triple.isPS4CPU())
     return false;
 
-  return shouldUseFramePointerForTarget(Args, Triple);
+  return useFramePointerForTargetByDefault(Args, Triple);
 }
 
 /// Add a CC1 option to specify the debug compilation directory.