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

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-aarch64

@llvm/pr-subscribers-backend-arm

Author: Benjamin Maxwell (MacDue)

<details>
<summary>Changes</summary>

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.

---
Full diff: https://github.com/llvm/llvm-project/pull/124750.diff


2 Files Affected:

- (modified) clang/lib/Sema/SemaARM.cpp (+6-3) 
- (added) clang/test/Sema/aarch64-incompat-sm-builtin-calls.cpp (+47) 


``````````diff
diff --git a/clang/lib/Sema/SemaARM.cpp b/clang/lib/Sema/SemaARM.cpp
index 2620bbc97ba02a..df865d1b7df8c1 100644
--- a/clang/lib/Sema/SemaARM.cpp
+++ b/clang/lib/Sema/SemaARM.cpp
@@ -650,7 +650,8 @@ 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) {
@@ -690,7 +691,8 @@ 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) {
@@ -719,7 +721,8 @@ 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:
diff --git a/clang/test/Sema/aarch64-incompat-sm-builtin-calls.cpp b/clang/test/Sema/aarch64-incompat-sm-builtin-calls.cpp
new file mode 100644
index 00000000000000..12ef7ad06b68b1
--- /dev/null
+++ b/clang/test/Sema/aarch64-incompat-sm-builtin-calls.cpp
@@ -0,0 +1,47 @@
+// RUN: %clang_cc1  -triple aarch64-none-linux-gnu -target-feature +sve \
+// RUN:   -target-feature +sme -target-feature +neon -x c++ -std=c++20 -Waarch64-sme-attributes -fsyntax-only -verify %s
+
+// REQUIRES: aarch64-registered-target
+
+#include <arm_sme.h>
+#include <arm_neon.h>
+
+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 at +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 at +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 at +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));
+  }();
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/124750