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

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Sam Tebbs (SamTebbs33)

<details>
<summary>Changes</summary>

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.

---
Full diff: https://github.com/llvm/llvm-project/pull/73672.diff


3 Files Affected:

- (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+3) 
- (modified) clang/lib/Sema/SemaChecking.cpp (+81) 
- (added) clang/test/Sema/aarch64-incompat-sm-builtin-calls.c (+24) 


``````````diff
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 9a7dafa4a298273..e2b7a695322c14b 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/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<
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index ae588db02bbe722..07937047a2843b0 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -2993,6 +2993,62 @@ static QualType getNeonEltType(NeonTypeFlags Flags, ASTContext &Context,
   llvm_unreachable("Invalid NeonTypeFlag!");
 }
 
+enum ArmStreamingType {
+  ArmNonStreaming,
+  ArmStreaming,
+  ArmStreamingCompatible,
+  ArmLocallyStreaming,
+  ArmStreamingOrSVE2p1
+};
+
+static ArmStreamingType getArmStreamingFnType(const FunctionDecl *FD) {
+  if (FD->hasAttr<ArmLocallyStreamingAttr>())
+    return ArmLocallyStreaming;
+  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) {
+  assert(BuiltinType != ArmLocallyStreaming &&
+         "Unexpected locally_streaming attribute for builtin!");
+
+  ArmStreamingType FnType = getArmStreamingFnType(FD);
+  if (BuiltinType == ArmStreamingOrSVE2p1) {
+    // Check intrinsics that are available in [sve2p1 or sme/sme2].
+    llvm::StringMap<bool> CallerFeatureMap;
+    S.Context.getFunctionFeatureMap(CallerFeatureMap, FD);
+    if (Builtin::evaluateRequiredTargetFeatures("sve2p1", CallerFeatureMap))
+      BuiltinType = ArmStreamingCompatible;
+    else
+      BuiltinType = ArmStreaming;
+  }
+
+  if ((FnType == ArmStreaming || FnType == ArmLocallyStreaming) &&
+      BuiltinType == ArmNonStreaming) {
+    S.Diag(TheCall->getBeginLoc(), diag::warn_attribute_arm_sm_incompat_builtin)
+        << TheCall->getSourceRange() << "streaming or locally streaming";
+  }
+
+  if ((FnType == ArmStreamingCompatible) &&
+      BuiltinType != ArmStreamingCompatible) {
+    S.Diag(TheCall->getBeginLoc(), diag::warn_attribute_arm_sm_incompat_builtin)
+        << TheCall->getSourceRange() << "streaming compatible";
+    return;
+  }
+
+  if (FnType == ArmNonStreaming && BuiltinType == ArmStreaming) {
+    S.Diag(TheCall->getBeginLoc(), diag::warn_attribute_arm_sm_incompat_builtin)
+        << TheCall->getSourceRange() << "non-streaming";
+  }
+}
+
 bool Sema::CheckSVEBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
   // Range check SVE intrinsics that take immediate values.
   SmallVector<std::tuple<int,int,int>, 3> ImmChecks;
@@ -3136,6 +3192,31 @@ bool Sema::CheckSVEBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
 
 bool Sema::CheckNeonBuiltinFunctionCall(const TargetInfo &TI,
                                         unsigned BuiltinID, CallExpr *TheCall) {
+  if (const FunctionDecl *FD = getCurFunctionDecl()) {
+    std::optional<ArmStreamingType> BuiltinType;
+
+    bool IsNeon = false;
+    switch (BuiltinID) {
+    default:
+      break;
+#define GET_NEON_BUILTINS
+#define TARGET_BUILTIN(id, x, y, z)                                            \
+  case NEON::BI##id:                                                           \
+    IsNeon = true;                                                             \
+    break;
+#define BUILTIN(id, x, y) TARGET_BUILTIN(id, x, y, "");
+#include "clang/Basic/arm_neon.inc"
+#undef TARGET_BUILTIN
+#undef BUILTIN
+#undef GET_NEON_BUILTINS
+    }
+
+    if (IsNeon) {
+      checkArmStreamingBuiltin(*this, TheCall, FD, ArmNonStreaming);
+      return true;
+    }
+  }
+
   llvm::APSInt Result;
   uint64_t mask = 0;
   unsigned TV = 0;
diff --git a/clang/test/Sema/aarch64-incompat-sm-builtin-calls.c b/clang/test/Sema/aarch64-incompat-sm-builtin-calls.c
new file mode 100644
index 000000000000000..08ed22917da67ca
--- /dev/null
+++ b/clang/test/Sema/aarch64-incompat-sm-builtin-calls.c
@@ -0,0 +1,24 @@
+// 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"
+#include "arm_sme_draft_spec_subject_to_change.h"
+#include "arm_sve.h"
+
+int16x8_t incompat_neon_sm(int16x8_t splat) __arm_streaming {
+  // expected-warning at +1 {{builtin call has undefined behaviour when called from a streaming or locally 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 at +1 {{builtin call has undefined behaviour when called from a streaming or locally 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 at +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);
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/73672