[clang][sema][FMV] Forbid multi-versioning arm_streaming functions. (#81268)

The streaming mode change is incompatible with the ifunc mechanism used
to implement FMV: we can't conditionally change it based on the
particular callee that is resolved at runtime.

Fixes: #80077

Author: jroelofs

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -3728,6 +3728,8 @@ def err_sme_definition_using_zt0_in_non_sme2_target : Error<
   "function using ZT0 state requires 'sme2'">;
 def err_conflicting_attributes_arm_state : Error<
   "conflicting attributes for state '%0'">;
+def err_sme_streaming_cannot_be_multiversioned : Error<
+  "streaming function cannot be multi-versioned">;
 def err_unknown_arm_state : Error<
   "unknown state '%0'">;
 def err_missing_arm_state : Error<

clang/include/clang/Sema/Sema.h

@@ -4838,13 +4838,12 @@ class Sema final {
   llvm::Error isValidSectionSpecifier(StringRef Str);
   bool checkSectionName(SourceLocation LiteralLoc, StringRef Str);
   bool checkTargetAttr(SourceLocation LiteralLoc, StringRef Str);
-  bool checkTargetVersionAttr(SourceLocation LiteralLoc, StringRef &Str,
-                              bool &isDefault);
-  bool
-  checkTargetClonesAttrString(SourceLocation LiteralLoc, StringRef Str,
-                              const StringLiteral *Literal, bool &HasDefault,
-                              bool &HasCommas, bool &HasNotDefault,
-                              SmallVectorImpl<SmallString<64>> &StringsBuffer);
+  bool checkTargetVersionAttr(SourceLocation LiteralLoc, Decl *D,
+                              StringRef &Str, bool &isDefault);
+  bool checkTargetClonesAttrString(
+      SourceLocation LiteralLoc, StringRef Str, const StringLiteral *Literal,
+      Decl *D, bool &HasDefault, bool &HasCommas, bool &HasNotDefault,
+      SmallVectorImpl<SmallString<64>> &StringsBuffer);
   bool checkMSInheritanceAttrOnDefinition(
       CXXRecordDecl *RD, SourceRange Range, bool BestCase,
       MSInheritanceModel SemanticSpelling);

clang/lib/Sema/SemaDeclAttr.cpp

@@ -3501,9 +3501,16 @@ bool Sema::checkTargetAttr(SourceLocation LiteralLoc, StringRef AttrStr) {
   return false;
 }
 
+static bool hasArmStreamingInterface(const FunctionDecl *FD) {
+  if (const auto *T = FD->getType()->getAs<FunctionProtoType>())
+    if (T->getAArch64SMEAttributes() & FunctionType::SME_PStateSMEnabledMask)
+      return true;
+  return false;
+}
+
 // Check Target Version attrs
-bool Sema::checkTargetVersionAttr(SourceLocation LiteralLoc, StringRef &AttrStr,
-                                  bool &isDefault) {
+bool Sema::checkTargetVersionAttr(SourceLocation LiteralLoc, Decl *D,
+                                  StringRef &AttrStr, bool &isDefault) {
   enum FirstParam { Unsupported };
   enum SecondParam { None };
   enum ThirdParam { Target, TargetClones, TargetVersion };
@@ -3519,6 +3526,8 @@ bool Sema::checkTargetVersionAttr(SourceLocation LiteralLoc, StringRef &AttrStr,
       return Diag(LiteralLoc, diag::warn_unsupported_target_attribute)
              << Unsupported << None << CurFeature << TargetVersion;
   }
+  if (hasArmStreamingInterface(cast<FunctionDecl>(D)))
+    return Diag(LiteralLoc, diag::err_sme_streaming_cannot_be_multiversioned);
   return false;
 }
 
@@ -3527,7 +3536,7 @@ static void handleTargetVersionAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   SourceLocation LiteralLoc;
   bool isDefault = false;
   if (!S.checkStringLiteralArgumentAttr(AL, 0, Str, &LiteralLoc) ||
-      S.checkTargetVersionAttr(LiteralLoc, Str, isDefault))
+      S.checkTargetVersionAttr(LiteralLoc, D, Str, isDefault))
     return;
   // Do not create default only target_version attribute
   if (!isDefault) {
@@ -3550,7 +3559,7 @@ static void handleTargetAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
 
 bool Sema::checkTargetClonesAttrString(
     SourceLocation LiteralLoc, StringRef Str, const StringLiteral *Literal,
-    bool &HasDefault, bool &HasCommas, bool &HasNotDefault,
+    Decl *D, bool &HasDefault, bool &HasCommas, bool &HasNotDefault,
     SmallVectorImpl<SmallString<64>> &StringsBuffer) {
   enum FirstParam { Unsupported, Duplicate, Unknown };
   enum SecondParam { None, CPU, Tune };
@@ -3619,6 +3628,9 @@ bool Sema::checkTargetClonesAttrString(
           HasNotDefault = true;
         }
       }
+      if (hasArmStreamingInterface(cast<FunctionDecl>(D)))
+        return Diag(LiteralLoc,
+                    diag::err_sme_streaming_cannot_be_multiversioned);
     } else {
       // Other targets ( currently X86 )
       if (Cur.starts_with("arch=")) {
@@ -3670,7 +3682,7 @@ static void handleTargetClonesAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
     if (!S.checkStringLiteralArgumentAttr(AL, I, CurStr, &LiteralLoc) ||
         S.checkTargetClonesAttrString(
             LiteralLoc, CurStr,
-            cast<StringLiteral>(AL.getArgAsExpr(I)->IgnoreParenCasts()),
+            cast<StringLiteral>(AL.getArgAsExpr(I)->IgnoreParenCasts()), D,
             HasDefault, HasCommas, HasNotDefault, StringsBuffer))
       return;
   }

clang/test/Sema/aarch64-sme-func-attrs.c

@@ -454,3 +454,43 @@ void unimplemented_spill_fill_za(void (*share_zt0_only)(void) __arm_inout("zt0")
   // expected-note@+1 {{add '__arm_preserves("za")' to the callee if it preserves ZA}}
   share_zt0_only();
 }
+
+// expected-cpp-error@+2 {{streaming function cannot be multi-versioned}}
+// expected-error@+1 {{streaming function cannot be multi-versioned}}
+__attribute__((target_version("sme2")))
+void cannot_work_version(void) __arm_streaming {}
+// expected-cpp-error@+5 {{function declared 'void ()' was previously declared 'void () __arm_streaming', which has different SME function attributes}}
+// expected-cpp-note@-2 {{previous declaration is here}}
+// expected-error@+3 {{function declared 'void (void)' was previously declared 'void (void) __arm_streaming', which has different SME function attributes}}
+// expected-note@-4 {{previous declaration is here}}
+__attribute__((target_version("default")))
+void cannot_work_version(void) {}
+
+
+// expected-cpp-error@+2 {{streaming function cannot be multi-versioned}}
+// expected-error@+1 {{streaming function cannot be multi-versioned}}
+__attribute__((target_clones("sme2")))
+void cannot_work_clones(void) __arm_streaming {}
+
+
+__attribute__((target("sme2")))
+void just_fine_streaming(void) __arm_streaming {}
+__attribute__((target_version("sme2")))
+void just_fine(void) { just_fine_streaming(); }
+__attribute__((target_version("default")))
+void just_fine(void) {}
+
+
+__arm_locally_streaming
+__attribute__((target_version("sme2")))
+void just_fine_locally_streaming(void) {}
+__attribute__((target_version("default")))
+void just_fine_locally_streaming(void) {}
+
+
+void fmv_caller() {
+    cannot_work_version();
+    cannot_work_clones();
+    just_fine();
+    just_fine_locally_streaming();
+}