[Clang]Throw frontend error for target feature mismatch when using flatten attribute

[abhishek-kaushik22]

Fixes #149866

[llvmbot]

@llvm/pr-subscribers-clang-codegen

@llvm/pr-subscribers-clang

Author: Abhishek Kaushik (abhishek-kaushik22)

Changes

Fixes #149866

---

Full diff: https://github.com/llvm/llvm-project/pull/150044.diff

2 Files Affected:

• (modified) clang/lib/CodeGen/CGCall.cpp (+5-3)
• (added) clang/test/CodeGen/target-features-error-3.c (+12)

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 0bceecec6e555..589716460b2de 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -5232,9 +5232,11 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
     // since otherwise we could be making a conditional call after a check for
     // the proper cpu features (and it won't cause code generation issues due to
     // function based code generation).
-    if (TargetDecl->hasAttr<AlwaysInlineAttr>() &&
-        (TargetDecl->hasAttr<TargetAttr>() ||
-         (CurFuncDecl && CurFuncDecl->hasAttr<TargetAttr>())))
+    if ((TargetDecl->hasAttr<AlwaysInlineAttr>() &&
+         (TargetDecl->hasAttr<TargetAttr>() ||
+          (CurFuncDecl && CurFuncDecl->hasAttr<TargetAttr>()))) ||
+        (CurFuncDecl && CurFuncDecl->hasAttr<FlattenAttr>() &&
+         TargetDecl->hasAttr<TargetAttr>()))
       checkTargetFeatures(Loc, FD);
   }
 
diff --git a/clang/test/CodeGen/target-features-error-3.c b/clang/test/CodeGen/target-features-error-3.c
new file mode 100644
index 0000000000000..8900edfa257c7
--- /dev/null
+++ b/clang/test/CodeGen/target-features-error-3.c
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 %s -triple=x86_64-linux-gnu -S -verify -o -
+
+typedef double __v2df __attribute__((__vector_size__(16)));
+
+__v2df __attribute__((target("sse4.1"))) foo() {
+    __v2df v = {0.0, 0.0};
+    return __builtin_ia32_roundpd(v, 2);
+}
+
+__v2df __attribute__((flatten)) bar() {
+    return foo(); // expected-error {{always_inline function 'foo' requires target feature 'sse4.1', but would be inlined into function 'bar' that is compiled without support for 'sse4.1'}}
+}

[abhishek-kaushik22]

@topperc can you please review since you've reviewed similar commits in the past?

[efriedma-quic]

Do we also need the CurFuncDecl && CurFuncDecl->hasAttr<TargetAttr>() check for flatten?

[abhishek-kaushik22]

From what I understand, we only need to check that the callee function has TargetAttr because the error is inlining a function that uses a target feature which the caller isn't compiled for. The caller having TargetAttr isn't required to reproduce the crash.

[efriedma-quic]

I think maybe in some weird cases, you can use a target attribute to remove features?

Anyway, if we need the check for always_inline, we probably also need it for flatten.

[efriedma-quic]

(The condition for always_inline is that either the callee has a TargetAttr, or the caller has a TargetAttr.)

[efriedma-quic]

Diagnostic refers to always_inline?

[abhishek-kaushik22]

This is coming from tablegen, do you think we should change that as well?

def err_function_needs_feature : Error<
  "always_inline function %1 requires target feature '%2', but would "
  "be inlined into function %0 that is compiled without support for '%2'">;

[efriedma-quic]

Yes.

Probably simplest to define a new error so you can use different phrasing.