[llvm][AArch64] Autoupgrade function attributes from Module attributes.

llvm/include/llvm/IR/AutoUpgrade.h

@@ -67,7 +67,8 @@ namespace llvm {
   void UpgradeSectionAttributes(Module &M);
 
   /// Correct any IR that is relying on old function attribute behavior.
-  void UpgradeFunctionAttributes(Function &F);
+  void UpgradeFunctionAttributes(Function &F,
+                                 bool ModuleMetadataIsMaterialized = false);
 
   /// If the given TBAA tag uses the scalar TBAA format, create a new node
   /// corresponding to the upgrade to the struct-path aware TBAA format.

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -6705,7 +6705,7 @@ Error BitcodeReader::materialize(GlobalValue *GV) {
   }
 
   // Look for functions that rely on old function attribute behavior.
-  UpgradeFunctionAttributes(*F);
+  UpgradeFunctionAttributes(*F, true);
 
   // Bring in any functions that this function forward-referenced via
   // blockaddresses.

llvm/lib/IR/AutoUpgrade.cpp

@@ -5155,7 +5155,46 @@ struct StrictFPUpgradeVisitor : public InstVisitor<StrictFPUpgradeVisitor> {
 };
 } // namespace
 
-void llvm::UpgradeFunctionAttributes(Function &F) {
+// Check if the module attribute is present and not zero.
+static bool isModuleAttributeSet(const Module *M, const StringRef &ModAttr) {
+  const auto *Attr =
+      mdconst::extract_or_null<ConstantInt>(M->getModuleFlag(ModAttr));
+  return Attr && Attr->getZExtValue();
+}
+
+// Copy an attribute from module to the function if exists.
+// First value of the pair is used when the module attribute is not zero
+// the second otherwise.
+static void
+CopyModuleAttributeToFunction(Function &F, StringRef FnAttrName,
+                              StringRef ModAttrName,
+                              std::pair<StringRef, StringRef> Values) {
+  if (F.hasFnAttribute(FnAttrName))
+    return;
+  F.addFnAttr(FnAttrName, isModuleAttributeSet(F.getParent(), ModAttrName)
+                              ? Values.first
+                              : Values.second);
+}
+
+// Copy a boolean attribute from module to the function if exists.
+// Module attribute treated false if zero otherwise true.
+static void CopyModuleAttributeToFunction(Function &F, StringRef AttrName) {
+  CopyModuleAttributeToFunction(
+      F, AttrName, AttrName,
+      std::make_pair<StringRef, StringRef>("true", "false"));
+}
+
+// Copy an attribute from module to the function if exists.
+// First value of the pair is used when the module attribute is not zero
+// the second otherwise.
+static void
+CopyModuleAttributeToFunction(Function &F, StringRef AttrName,
+                              std::pair<StringRef, StringRef> Values) {
+  CopyModuleAttributeToFunction(F, AttrName, AttrName, Values);
+}
+
+void llvm::UpgradeFunctionAttributes(Function &F,
+                                     bool ModuleMetadataIsMaterialized) {
   // If a function definition doesn't have the strictfp attribute,
   // convert any callsite strictfp attributes to nobuiltin.
   if (!F.isDeclaration() && !F.hasFnAttribute(Attribute::StrictFP)) {
@@ -5167,6 +5206,37 @@ void llvm::UpgradeFunctionAttributes(Function &F) {
   F.removeRetAttrs(AttributeFuncs::typeIncompatible(F.getReturnType()));
   for (auto &Arg : F.args())
     Arg.removeAttrs(AttributeFuncs::typeIncompatible(Arg.getType()));
+
+  if (!ModuleMetadataIsMaterialized)
+    return;
+  if (F.isDeclaration())
+    return;
+  Module *M = F.getParent();
+  if (!M)
+    return;
+
+  Triple T(M->getTargetTriple());
+  // Convert module level attributes to function level attributes because
+  // after merging modules the attributes might change and would have different
+  // effect on the functions as the original module would have.
+  if (T.isThumb() || T.isARM() || T.isAArch64()) {
+    if (!F.hasFnAttribute("sign-return-address")) {
+      StringRef SignType = "none";
+      if (isModuleAttributeSet(M, "sign-return-address"))
+        SignType = "non-leaf";
+
+      if (isModuleAttributeSet(M, "sign-return-address-all"))
+        SignType = "all";
+
+      F.addFnAttr("sign-return-address", SignType);
+    }
+    CopyModuleAttributeToFunction(F, "branch-target-enforcement");
+    CopyModuleAttributeToFunction(F, "branch-protection-pauth-lr");
+    CopyModuleAttributeToFunction(F, "guarded-control-stack");
+    CopyModuleAttributeToFunction(
+        F, "sign-return-address-key",
+        std::make_pair<StringRef, StringRef>("b_key", "a_key"));
+  }
 }
 
 static bool isOldLoopArgument(Metadata *MD) {

llvm/lib/Linker/IRMover.cpp

@@ -1606,6 +1606,10 @@ Error IRLinker::run() {
   // Loop over all of the linked values to compute type mappings.
   computeTypeMapping();
 
+  // Update function attributes before copying them to destation module.
+  for (Function &F : SrcM->getFunctionList())
+    UpgradeFunctionAttributes(F, true);
+
   std::reverse(Worklist.begin(), Worklist.end());
   while (!Worklist.empty()) {
     GlobalValue *GV = Worklist.back();

llvm/test/Bitcode/upgrade-arc-runtime-calls.ll

@@ -55,7 +55,7 @@ unwindBlock:
 // Check that auto-upgrader converts function calls to intrinsic calls. Note that
 // the auto-upgrader doesn't touch invoke instructions.
 
-// ARC: define void @testRuntimeCalls(ptr %[[A:.*]], ptr %[[B:.*]], ptr %[[C:.*]], ptr %[[D:.*]], ptr %[[E:.*]]) personality
+// ARC: define void @testRuntimeCalls(ptr %[[A:.*]], ptr %[[B:.*]], ptr %[[C:.*]], ptr %[[D:.*]], ptr %[[E:.*]]) #0 personality
 // ARC: %[[V0:.*]] = tail call ptr @llvm.objc.autorelease(ptr %[[A]])
 // ARC-NEXT: tail call void @llvm.objc.autoreleasePoolPop(ptr %[[A]])
 // ARC-NEXT: %[[V1:.*]] = tail call ptr @llvm.objc.autoreleasePoolPush()
@@ -88,7 +88,7 @@ unwindBlock:
 // ARC-NEXT: tail call void @llvm.objc.arc.annotation.bottomup.bbend(ptr %[[B]], ptr %[[C]])
 // ARC-NEXT: invoke void @objc_autoreleasePoolPop(ptr %[[A]])
 
-// NOUPGRADE: define void @testRuntimeCalls(ptr %[[A:.*]], ptr %[[B:.*]], ptr %[[C:.*]], ptr %[[D:.*]], ptr %[[E:.*]]) personality
+// NOUPGRADE: define void @testRuntimeCalls(ptr %[[A:.*]], ptr %[[B:.*]], ptr %[[C:.*]], ptr %[[D:.*]], ptr %[[E:.*]]) #0 personality
 // NOUPGRADE: %[[V0:.*]] = tail call ptr @objc_autorelease(ptr %[[A]])
 // NOUPGRADE-NEXT: tail call void @objc_autoreleasePoolPop(ptr %[[A]])
 // NOUPGRADE-NEXT: %[[V1:.*]] = tail call ptr @objc_autoreleasePoolPush()

llvm/test/LTO/AArch64/link-branch-target-enforcement.ll

@@ -32,6 +32,7 @@ entry:
 ; CHECK-DUMP: <main>:
 ; CHECK-DUMP:      bl      0x8 <main+0x8>
 ; CHECK-DUMP: <foo>:
+; CHECK-DUMP:     paciasp
 
 ; `main` doesn't support BTI while `foo` does, so in the binary
 ; we should see only PAC which is supported by both.

llvm/test/LTO/AArch64/link-sign-return-address.ll

@@ -0,0 +1,43 @@
+; Testcase to check that module with different branch-target-enforcement can
+; be mixed.
+;
+; RUN: llvm-as %s -o %t1.bc
+; RUN: llvm-as %p/Inputs/foo.ll -o %t2.bc
+; RUN: llvm-lto -exported-symbol main \
+; RUN:          -exported-symbol foo \
+; RUN:          -filetype=obj \
+; RUN:           %t2.bc %t1.bc \
+; RUN:           -o %t1.exe 2>&1
+; RUN: llvm-objdump -d %t1.exe | FileCheck --check-prefix=CHECK-DUMP %s
+; RUN: llvm-readelf -n %t1.exe | FileCheck --allow-empty --check-prefix=CHECK-PROP %s
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-unknown-linux-gnu"
+
+declare i32 @foo();
+
+define i32 @main() {
+entry:
+  %add = call i32 @foo()
+  ret i32 %add
+}
+
+!llvm.module.flags = !{!0, !1, !2, !3 }
+!0 = !{i32 8, !"branch-target-enforcement", i32 0}
+!1 = !{i32 8, !"sign-return-address", i32 0}
+!2 = !{i32 8, !"sign-return-address-all", i32 0}
+!3 = !{i32 8, !"sign-return-address-with-bkey", i32 0}
+
+; CHECK-DUMP: <foo>:
+; CHECK-DUMP:     paciasp
+; CHECK-DUMP:     mov     w0, #0x2a
+; CHECK-DUMP:     autiasp
+; CHECK-DUMP:     ret
+; CHECK-DUMP: <main>:
+; CHECK-DUMP-NOT:  paciasp
+; CHECK-DUMP:      str     x30,
+; CHECK-DUMP:      bl      0x14 <main+0x4>
+
+; `main` doesn't support PAC sign-return-address while `foo` does, so in the binary
+; we should not see anything.
+; CHECK-PROP-NOT:   Properties: aarch64 feature: PAC

llvm/test/Linker/link-arm-and-thumb.ll

@@ -13,11 +13,12 @@ entry:
   ret i32 %add
 }
 
-; CHECK: define i32 @main() {
+; CHECK: define i32 @main() [[MAIN_ATTRS:#[0-9]+]]
 ; CHECK: define i32 @foo(i32 %a, i32 %b) [[ARM_ATTRS:#[0-9]+]]
 ; CHECK: define i32 @bar(i32 %a, i32 %b) [[THUMB_ATTRS:#[0-9]+]]
 
-; CHECK: attributes [[ARM_ATTRS]] = { "target-features"="-thumb-mode" }
-; CHECK: attributes [[THUMB_ATTRS]] = { "target-features"="+thumb-mode" }
+; CHECK: attributes [[MAIN_ATTRS]] = { {{.*}} }
+; CHECK: attributes [[ARM_ATTRS]] = { {{.*}} "target-features"="-thumb-mode" }
+; CHECK: attributes [[THUMB_ATTRS]] = { {{.*}} "target-features"="+thumb-mode" }
 
 ; STDERR-NOT: warning: Linking two modules of different target triples: