[IR][sanitizer] Add module flag "frame-pointer" and set it for cc1 -mframe-pointer={non-leaf,all}

[MaskRay]

Summary

The Linux kernel objtool diagnostic call without frame pointer save/setup
arise in multiple instrumentation passes (asan/tsan/gcov). With the mechanism
introduced in D100251, it's trivial to respect the command line
-m[no-]omit-leaf-frame-pointer/-f[no-]omit-frame-pointer, so let's do it.

Fix: https://github.com/ClangBuiltLinux/linux/issues/1236 (tsan)
Fix: https://github.com/ClangBuiltLinux/linux/issues/1238 (asan)

[nickdesaulniers]

Nice idea to create Function::createWithDefaultAttr then reuse for multiple purposes!

llvm/lib/IR/Function.cpp

333

we should call this from gcov too to solve https://github.com/ClangBuiltLinux/linux/issues/955.

[vitalybuka]

llvm/include/llvm/IR/Module.h

896

It should be enum, similar to PIELevel.

And probably needs IR documentation update?

[vitalybuka]

llvm/lib/IR/Function.cpp

346

Should these be added into Attribute:: ?

[MaskRay]

use enum.
add doc.

[MaskRay]

llvm/lib/IR/Function.cpp

333

Exactly:) Planned to do it after this patch https://github.com/ClangBuiltLinux/linux/issues/1238#issuecomment-824517092

346

The function attribute "frame-pointer" is already used, with a string value. A regular attribute cannot have a string value so it was created as the string form...

The documentation is long overdue, though. I have added a bit documentation.

[MaskRay]

llvm/docs/LangRef.rst

7019 ↗

(On Diff #339760)

I'll add:

These metadata correspond to a few function attributes with significant code generation behaviors. Function attributes with just optimization purposes should not be listed because the performance impact of these synthesized functions is small.

[ychen]

LGTM

[MaskRay]

Chatted offline, vitalybuka said I can go ahead with existing ack.

[MaskRay]

improve doc

clang/lib/CodeGen/CodeGenModule.cpp

if (getCodeGenOpts().CodeModel.size() > 0) {
     }
   }
 
   if (CodeGenOpts.NoPLT)
     getModule().setRtLibUseGOT();
   if (CodeGenOpts.UnwindTables)
     getModule().setUwtable();
 
+  switch (CodeGenOpts.getFramePointer()) {
+  case CodeGenOptions::FramePointerKind::None:
+    // 0 is the default.
+    break;
+  case CodeGenOptions::FramePointerKind::NonLeaf:
+    getModule().setFramePointer(1);
+    break;
+  case CodeGenOptions::FramePointerKind::All:
+    getModule().setFramePointer(2);
+    break;
+  }
+
   SimplifyPersonality();
 
   if (getCodeGenOpts().EmitDeclMetadata)
     EmitDeclMetadata();
 
   if (getCodeGenOpts().EmitGcovArcs || getCodeGenOpts().EmitGcovNotes)
     EmitCoverageFile();
 

clang/test/CodeGen/asan-frame-pointer.cpp

+/// -mframe-pointer=none sets the module flag "frame-pointer" (merge behavior: max).
+/// asan synthesized ctor/dtor get the "frame-pointer" function attribute if not zero (default).
+// RUN: %clang_cc1 -emit-llvm -fsanitize=address -mframe-pointer=none %s -o - | FileCheck %s --check-prefix=NONE
+// RUN: %clang_cc1 -emit-llvm -fsanitize=address -mframe-pointer=non-leaf %s -o - | FileCheck %s --check-prefix=NONLEAF
+// RUN: %clang_cc1 -emit-llvm -fsanitize=address -mframe-pointer=all %s -o - | FileCheck %s --check-prefix=ALL
+
+int global;
+
+// NONE: define internal void @asan.module_ctor() #[[#ATTR:]] {
+// NONE: define internal void @asan.module_dtor() #[[#ATTR]] {
+// NONE: attributes #[[#ATTR]] = { nounwind }
+
+// NONLEAF: define internal void @asan.module_ctor() #[[#ATTR:]] {
+// NONLEAF: define internal void @asan.module_dtor() #[[#ATTR]] {
+// NONLEAF: attributes #[[#ATTR]] = { nounwind "frame-pointer"="non-leaf" }
+
+// ALL: define internal void @asan.module_ctor() #[[#ATTR:]] {
+// ALL: define internal void @asan.module_dtor() #[[#ATTR]] {
+// ALL: attributes #[[#ATTR]] = { nounwind "frame-pointer"="all" }

llvm/include/llvm/IR/Module.h

/// @}
 
   /// Set that PLT should be avoid for RTLib calls.
   void setRtLibUseGOT();
 
   /// Get/set whether synthesized functions should get the uwtable attribute.
   bool getUwtable() const;
   void setUwtable();
 
+  /// Get/set whether synthesized functions should get the "frame-pointer"
+  /// attribute.
+  int getFramePointer() const;
+  void setFramePointer(int V);
+
   /// @name Utility functions for querying and setting the build SDK version
   /// @{
 
   /// Attach a build SDK version metadata to this module.
   void setSDKVersion(const VersionTuple &V);
 
   /// Get the build SDK version metadata.
   ///

llvm/lib/IR/Function.cpp

unsigned Function::getInstructionCount() const {
   return NumInstrs;
 }
 
 Function *Function::Create(FunctionType *Ty, LinkageTypes Linkage,
                            const Twine &N, Module &M) {
   return Create(Ty, Linkage, M.getDataLayout().getProgramAddressSpace(), N, &M);
 }
 
 Function *Function::createWithDefaultAttr(FunctionType *Ty,
                                           LinkageTypes Linkage,
                                           unsigned AddrSpace, const Twine &N,
                                           Module *M) {
   auto *F = new Function(Ty, Linkage, AddrSpace, N, M);
+  AttrBuilder B;
   if (M->getUwtable())
-    F->addAttribute(AttributeList::FunctionIndex, Attribute::UWTable);
+    B.addAttribute(Attribute::UWTable);
+  switch (M->getFramePointer()) {
+  case 0:
+    // 0 ("none") is the default.
+    break;
+  case 1:
+    B.addAttribute("frame-pointer", "non-leaf");
+    break;
+  case 2:
+    B.addAttribute("frame-pointer", "all");
+    break;
+  default:
+    llvm_unreachable("unknown \"frame-pointer\" value");
+  }
+  F->addAttributes(AttributeList::FunctionIndex, B);
   return F;
 }
 
 void Function::removeFromParent() {
   getParent()->getFunctionList().remove(getIterator());
 }
 
 void Function::eraseFromParent() {

llvm/lib/IR/Module.cpp

 
 bool Module::getUwtable() const {
   auto *Val = cast_or_null<ConstantAsMetadata>(getModuleFlag("uwtable"));
   return Val && (cast<ConstantInt>(Val->getValue())->getZExtValue() > 0);
 }
 
 void Module::setUwtable() { addModuleFlag(ModFlagBehavior::Max, "uwtable", 1); }
 
+int Module::getFramePointer() const {
+  auto *Val = cast_or_null<ConstantAsMetadata>(getModuleFlag("frame-pointer"));
+  return Val ? cast<ConstantInt>(Val->getValue())->getZExtValue() : 0;
+}
+
+void Module::setFramePointer(int V) {
+  addModuleFlag(ModFlagBehavior::Max, "frame-pointer", V);
+}
+
 void Module::setSDKVersion(const VersionTuple &V) {
   SmallVector<unsigned, 3> Entries;
   Entries.push_back(V.getMajor());
   if (auto Minor = V.getMinor()) {
     Entries.push_back(*Minor);
     if (auto Subminor = V.getSubminor())
       Entries.push_back(*Subminor);
     // Ignore the 'build' component as it can't be represented in the object

llvm/test/Instrumentation/AddressSanitizer/module-flags.ll

 ; RUN: opt < %s -passes='asan-pipeline' -S | FileCheck %s
 
 target triple = "x86_64-unknown-linux-gnu"
 
 @g = dso_local global i32 0, align 4
 
 define i32 @test_load() sanitize_address {
 entry:
   %tmp = load i32, i32* @g, align 4
   ret i32 %tmp
 }
 
-!llvm.module.flags = !{!0}
+!llvm.module.flags = !{!0, !1}
 
 ;; Due to -fasynchronous-unwind-tables.
 !0 = !{i32 7, !"uwtable", i32 1}
 
+;; Due to -fno-omit-frame-pointer.
+!1 = !{i32 7, !"frame-pointer", i32 2}
+
 ;; Set the uwtable attribute on ctor/dtor.
 ; CHECK: define internal void @asan.module_ctor() #[[#ATTR:]]
 ; CHECK: define internal void @asan.module_dtor() #[[#ATTR]]
-; CHECK: attributes #[[#ATTR]] = { nounwind uwtable }
+; CHECK: attributes #[[#ATTR]] = { nounwind uwtable "frame-pointer"="all" }