Only infer attributes for callees (not definitions)

This matches the old behaviour and allows stubbing the ABI routines
in C++.

Author: MacDue

llvm/lib/Target/AArch64/Utils/AArch64SMEAttributes.cpp

@@ -111,8 +111,13 @@ bool SMECallAttrs::requiresSMChange() const {
 }
 
 SMECallAttrs::SMECallAttrs(const CallBase &CB)
-    : CallerFn(*CB.getFunction()), CalledFn(CB.getCalledFunction()),
+    : CallerFn(*CB.getFunction()), CalledFn(SMEAttrs::Normal),
       Callsite(CB.getAttributes()), IsIndirect(CB.isIndirectCall()) {
+  if (auto *CalledFunction = CB.getCalledFunction()) {
+    CalledFn = SMEAttrs(*CalledFunction);
+    CalledFn.addKnownFunctionAttrs(CalledFunction->getName());
+  }
+
   // FIXME: We probably should not allow SME attributes on direct calls but
   // clang duplicates streaming mode attributes at each callsite.
   assert((IsIndirect ||

llvm/lib/Target/AArch64/Utils/AArch64SMEAttributes.h

@@ -16,6 +16,7 @@ namespace llvm {
 class Function;
 class CallBase;
 class AttributeList;
+class SMECallAttrs;
 
 /// SMEAttrs is a utility class to parse the SME ACLE attributes on functions.
 /// It helps determine a function's requirements for PSTATE.ZA and PSTATE.SM.
@@ -50,12 +51,7 @@ class SMEAttrs {
 
   SMEAttrs() = default;
   SMEAttrs(unsigned Mask) { set(Mask); }
-  SMEAttrs(const Function *F)
-      : SMEAttrs(F ? F->getAttributes() : AttributeList()) {
-    if (F)
-      addKnownFunctionAttrs(F->getName());
-  }
-  SMEAttrs(const Function &F) : SMEAttrs(&F) {}
+  SMEAttrs(const Function &F) : SMEAttrs(F.getAttributes()) {}
   SMEAttrs(const AttributeList &L);
   SMEAttrs(StringRef FuncName) { addKnownFunctionAttrs(FuncName); };
 
@@ -144,6 +140,8 @@ class SMEAttrs {
     return Bitmask == Other.Bitmask;
   }
 
+  friend SMECallAttrs;
+
 private:
   void addKnownFunctionAttrs(StringRef FuncName);
 };