[clang][SME] Account for C++ lambdas in SME builtin diagnostics (#124750)

A C++ lambda does not inherit attributes from the parent function. So
the SME builtin diagnostics should look at the lambda's attributes, not
the parent function's.

The fix is very simple and just adds the missing "AllowLambda" flag to
the function decl lookups.

Author: MacDue

clang/lib/Sema/SemaARM.cpp

@@ -636,7 +636,8 @@ static ArmSMEState getSMEState(unsigned BuiltinID) {
 
 bool SemaARM::CheckSMEBuiltinFunctionCall(unsigned BuiltinID,
                                           CallExpr *TheCall) {
-  if (const FunctionDecl *FD = SemaRef.getCurFunctionDecl()) {
+  if (const FunctionDecl *FD =
+          SemaRef.getCurFunctionDecl(/*AllowLambda=*/true)) {
     std::optional<ArmStreamingType> BuiltinType;
 
     switch (BuiltinID) {
@@ -676,7 +677,8 @@ bool SemaARM::CheckSMEBuiltinFunctionCall(unsigned BuiltinID,
 
 bool SemaARM::CheckSVEBuiltinFunctionCall(unsigned BuiltinID,
                                           CallExpr *TheCall) {
-  if (const FunctionDecl *FD = SemaRef.getCurFunctionDecl()) {
+  if (const FunctionDecl *FD =
+          SemaRef.getCurFunctionDecl(/*AllowLambda=*/true)) {
     std::optional<ArmStreamingType> BuiltinType;
 
     switch (BuiltinID) {
@@ -705,7 +707,8 @@ bool SemaARM::CheckSVEBuiltinFunctionCall(unsigned BuiltinID,
 bool SemaARM::CheckNeonBuiltinFunctionCall(const TargetInfo &TI,
                                            unsigned BuiltinID,
                                            CallExpr *TheCall) {
-  if (const FunctionDecl *FD = SemaRef.getCurFunctionDecl()) {
+  if (const FunctionDecl *FD =
+          SemaRef.getCurFunctionDecl(/*AllowLambda=*/true)) {
 
     switch (BuiltinID) {
     default:

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

@@ -1,5 +1,5 @@
 // NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
-// RUN: %clang_cc1  -triple aarch64-none-linux-gnu -target-feature +sve \
+// RUN: %clang_cc1  -std=c++23 -triple aarch64-none-linux-gnu -target-feature +sve \
 // RUN:   -target-feature +bf16 -target-feature +sve -target-feature +sme -target-feature +sme2 -target-feature +sve2 -target-feature +neon -Waarch64-sme-attributes -fsyntax-only -verify %s
 
 // REQUIRES: aarch64-registered-target
@@ -126,3 +126,69 @@ void missing_zt0(void) __arm_streaming {
 
 __arm_new("zt0")
 void new_zt0(void) __arm_streaming { svzero_zt(0); }
+
+/// C++ lambda tests:
+
+void use_streaming_builtin_in_lambda(uint32_t slice_base, svbool_t pg, const void *ptr) __arm_streaming __arm_out("za")
+{
+  [&]{
+    /// The lambda is its own function and does not inherit the SME attributes (so this should error).
+    // expected-error@+1 {{builtin can only be called from a streaming function}}
+    svld1_hor_za64(0, slice_base, pg, ptr);
+  }();
+}
+
+void use_streaming_builtin(uint32_t slice_base, svbool_t pg, const void *ptr) __arm_streaming __arm_out("za")
+{
+  /// Without the lambda the same builtin is okay (as the SME attributes apply).
+  svld1_hor_za64(0, slice_base, pg, ptr);
+}
+
+int16x8_t use_neon_builtin_sm(int16x8_t splat) __arm_streaming_compatible {
+  // expected-error@+1 {{builtin can only be called from a non-streaming function}}
+  return (int16x8_t)__builtin_neon_vqaddq_v((int8x16_t)splat, (int8x16_t)splat, 33);
+}
+
+int16x8_t use_neon_builtin_sm_in_lambda(int16x8_t splat) __arm_streaming_compatible {
+  return [&]{
+    /// This should not error (as we switch out of streaming mode to execute the lambda).
+    /// Note: The result int16x8_t is spilled and reloaded as a q-register.
+    return (int16x8_t)__builtin_neon_vqaddq_v((int8x16_t)splat, (int8x16_t)splat, 33);
+  }();
+}
+
+float use_incomp_sve_builtin_sm() __arm_streaming {
+  // expected-error@+1 {{builtin can only be called from a non-streaming function}}
+  return svadda(svptrue_b32(), 0, svdup_f32(1));
+}
+
+float incomp_sve_sm_fadda_sm_in_lambda(void) __arm_streaming {
+  return [&]{
+    /// This should work like the Neon builtin.
+    return svadda(svptrue_b32(), 0, svdup_f32(1));
+  }();
+}
+
+void use_streaming_builtin_in_streaming_lambda(uint32_t slice_base, const void *ptr)
+{
+  [&]  __arm_new("za") () __arm_streaming {
+    // Here the lambda is streaming with ZA state, so this is okay.
+    svld1_hor_za64(0, slice_base, svptrue_b64(), ptr);
+  }();
+}
+
+int16x8_t use_neon_builtin_in_streaming_lambda(int16x8_t splat) {
+  return [&]() __arm_streaming_compatible {
+    /// This should error as the lambda is streaming-compatible.
+    // expected-error@+1 {{builtin can only be called from a non-streaming function}}
+    return (int16x8_t)__builtin_neon_vqaddq_v((int8x16_t)splat, (int8x16_t)splat, 33);
+  }();
+}
+
+float incomp_sve_fadda_in_streaming_lambda(void) {
+  return [&]() __arm_streaming {
+    // Should error (like the Neon case above).
+    // expected-error@+1 {{builtin can only be called from a non-streaming function}}
+    return svadda(svptrue_b32(), 0, svdup_f32(1));
+  }();
+}