[llvm][ARM][AArch64] Add attributes to synthetic functions.

[DanielKristofKiss]

Module flags represent the original intention.

Depends on #82819

[llvmbot]

@llvm/pr-subscribers-llvm-ir

Author: Dani (DanielKristofKiss)

Changes

Module flags represent the original intention.

---

Full diff: https://github.com/llvm/llvm-project/pull/83153.diff

1 Files Affected:

• (modified) llvm/lib/IR/Function.cpp (+36)

diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
index 056e4f31981a72..5e217cc5680186 100644
--- a/llvm/lib/IR/Function.cpp
+++ b/llvm/lib/IR/Function.cpp
@@ -65,6 +65,8 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/ModRef.h"
+#include "llvm/TargetParser/ARMTargetParser.h"
+#include "llvm/TargetParser/Triple.h"
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
@@ -378,6 +380,40 @@ Function *Function::createWithDefaultAttr(FunctionType *Ty,
   }
   if (M->getModuleFlag("function_return_thunk_extern"))
     B.addAttribute(Attribute::FnRetThunkExtern);
+
+  Triple T(M->getTargetTriple());
+
+  auto Profile = llvm::ARM::parseArchProfile(T.getArchName());
+  if ((T.isArmT32() && Profile == llvm::ARM::ProfileKind::M) || T.isAArch64()) {
+    // Check if the module attribute is present and not zero.
+    auto isModuleAttributeSet = [&](const StringRef &ModAttr) -> bool {
+      const auto *Attr =
+          mdconst::extract_or_null<ConstantInt>(M->getModuleFlag(ModAttr));
+      return Attr && Attr->getZExtValue();
+    };
+
+    auto AddAttributeIfSet = [&](const StringRef &ModAttr) {
+      if (isModuleAttributeSet(ModAttr))
+        B.addAttribute(ModAttr, "true");
+    };
+
+    StringRef SignType = "none";
+    if (isModuleAttributeSet("sign-return-address"))
+      SignType = "non-leaf";
+    if (isModuleAttributeSet("sign-return-address-all"))
+      SignType = "all";
+    if (SignType != "none") {
+      B.addAttribute("sign-return-address", SignType);
+      if (T.isAArch64())
+        B.addAttribute("sign-return-address-key",
+                       isModuleAttributeSet("sign-return-address-with-bkey")
+                           ? "b_key"
+                           : "a_key");
+    }
+    AddAttributeIfSet("branch-target-enforcement");
+    AddAttributeIfSet("branch-protection-pauth-lr");
+    AddAttributeIfSet("guarded-control-stack");
+  }
   F->addFnAttrs(B);
   return F;
 }

[MaskRay]

test?

[nickdesaulniers]

Can both be set at the same time? Is there a verifier check to enforce that if not?

[DanielKristofKiss]

No, only one of them should present.
There is no check there in the verifier. I didn't see any obvious spot for it, I'll create something for it.

[DanielKristofKiss]

#83635 is about the verification.

[nickdesaulniers]

Perhaps you can avoid bringing in Triple.h and ARMTargetParser if we just always check for these attributes (even if they are arch specific? I guess I'm curious about the M profile check here. If we ran this on non-m-profile arm32, would the module attributes even ever exist?

[DanielKristofKiss]

That won't happen because the fronted won't add the flag, even it they present the backend won't do anything with them.

[DanielKristofKiss]

Depends on #82819

[tmatheson-arm]

LGTM. Please avoid force pushing, it makes reviewing more difficult because we can't see what changed since the last time.