[AArch64] Warn when calling a NEON builtin in a streaming function (#73672)

This patch introduces a warning that is emitted when a Neon builtin is
called from a streaming function, as that situation is not supported.

Uses work by Kerry McLaughlin.

Author: SamTebbs33

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -3148,6 +3148,9 @@ def err_attribute_bad_sve_vector_size : Error<
 def err_attribute_arm_feature_sve_bits_unsupported : Error<
   "%0 is only supported when '-msve-vector-bits=<bits>' is specified with a "
   "value of 128, 256, 512, 1024 or 2048.">;
+def warn_attribute_arm_sm_incompat_builtin : Warning<
+  "builtin call has undefined behaviour when called from a %0 function">,
+  InGroup<DiagGroup<"undefined-arm-streaming">>;
 def err_sve_vector_in_non_sve_target : Error<
   "SVE vector type %0 cannot be used in a target without sve">;
 def err_attribute_riscv_rvv_bits_unsupported : Error<

clang/lib/Sema/SemaChecking.cpp

@@ -2993,6 +2993,38 @@ static QualType getNeonEltType(NeonTypeFlags Flags, ASTContext &Context,
   llvm_unreachable("Invalid NeonTypeFlag!");
 }
 
+enum ArmStreamingType { ArmNonStreaming, ArmStreaming, ArmStreamingCompatible };
+
+static ArmStreamingType getArmStreamingFnType(const FunctionDecl *FD) {
+  if (FD->hasAttr<ArmLocallyStreamingAttr>())
+    return ArmStreaming;
+  if (const auto *T = FD->getType()->getAs<FunctionProtoType>()) {
+    if (T->getAArch64SMEAttributes() & FunctionType::SME_PStateSMEnabledMask)
+      return ArmStreaming;
+    if (T->getAArch64SMEAttributes() & FunctionType::SME_PStateSMCompatibleMask)
+      return ArmStreamingCompatible;
+  }
+  return ArmNonStreaming;
+}
+
+static void checkArmStreamingBuiltin(Sema &S, CallExpr *TheCall,
+                                     const FunctionDecl *FD,
+                                     ArmStreamingType BuiltinType) {
+  ArmStreamingType FnType = getArmStreamingFnType(FD);
+
+  if (FnType == ArmStreaming && BuiltinType == ArmNonStreaming) {
+    S.Diag(TheCall->getBeginLoc(), diag::warn_attribute_arm_sm_incompat_builtin)
+        << TheCall->getSourceRange() << "streaming";
+  }
+
+  if (FnType == ArmStreamingCompatible &&
+      BuiltinType != ArmStreamingCompatible) {
+    S.Diag(TheCall->getBeginLoc(), diag::warn_attribute_arm_sm_incompat_builtin)
+        << TheCall->getSourceRange() << "streaming compatible";
+    return;
+  }
+}
+
 bool Sema::CheckSVEBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
   // Range check SVE intrinsics that take immediate values.
   SmallVector<std::tuple<int,int,int>, 3> ImmChecks;
@@ -3148,6 +3180,23 @@ bool Sema::CheckSVEBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
 
 bool Sema::CheckNeonBuiltinFunctionCall(const TargetInfo &TI,
                                         unsigned BuiltinID, CallExpr *TheCall) {
+  if (const FunctionDecl *FD = getCurFunctionDecl()) {
+
+    switch (BuiltinID) {
+    default:
+      break;
+#define GET_NEON_BUILTINS
+#define TARGET_BUILTIN(id, ...) case NEON::BI##id:
+#define BUILTIN(id, ...) case NEON::BI##id:
+#include "clang/Basic/arm_neon.inc"
+      checkArmStreamingBuiltin(*this, TheCall, FD, ArmNonStreaming);
+      break;
+#undef TARGET_BUILTIN
+#undef BUILTIN
+#undef GET_NEON_BUILTINS
+    }
+  }
+
   llvm::APSInt Result;
   uint64_t mask = 0;
   unsigned TV = 0;

clang/test/Sema/aarch64-incompat-sm-builtin-calls.c

@@ -0,0 +1,22 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// RUN: %clang_cc1  -triple aarch64-none-linux-gnu -target-feature +sve \
+// RUN:   -target-feature +sme -target-feature +sve2 -target-feature +neon -fsyntax-only -verify %s
+
+// REQUIRES: aarch64-registered-target
+
+#include "arm_neon.h"
+
+int16x8_t incompat_neon_sm(int16x8_t splat) __arm_streaming {
+  // expected-warning@+1 {{builtin call has undefined behaviour when called from a streaming function}}
+  return (int16x8_t)__builtin_neon_vqaddq_v((int8x16_t)splat, (int8x16_t)splat, 33);
+}
+
+__arm_locally_streaming int16x8_t incompat_neon_ls(int16x8_t splat) {
+  // expected-warning@+1 {{builtin call has undefined behaviour when called from a streaming function}}
+  return (int16x8_t)__builtin_neon_vqaddq_v((int8x16_t)splat, (int8x16_t)splat, 33);
+}
+
+int16x8_t incompat_neon_smc(int16x8_t splat) __arm_streaming_compatible {
+  // expected-warning@+1 {{builtin call has undefined behaviour when called from a streaming compatible function}}
+  return (int16x8_t)__builtin_neon_vqaddq_v((int8x16_t)splat, (int8x16_t)splat, 33);
+}