[clang] [Clang] [Parser] Support [[omp::assume]] (PR #84582)

[via cfe-commits]

https://github.com/Sirraide created https://github.com/llvm/llvm-project/pull/84582

This pr implements the `[[omp::assume]]` spelling for the `__attribute__((assume))` attribute. It does not change anything about how that attribute is handled by the rest of Clang.

This pr is only *not* meant for figuring out what to do w/ the latter—I’ll be opening a separate pr that will update the documentation etc. to use `[[omp::assume]]`; we should have that discussion there; this pr is mostly meant to be self-contained (and also does not depend on or conflict with #81014).

>From d436f7fefb967f050220a8ede6d05c8e26f363b3 Mon Sep 17 00:00:00 2001
From: Sirraide <aeternalmail at gmail.com>
Date: Fri, 8 Mar 2024 23:54:14 +0100
Subject: [PATCH] [Clang] [Parser] Support [[omp::assume]]

---
 clang/include/clang/Basic/Attr.td |  2 +-
 clang/lib/Basic/Attributes.cpp    |  8 ++++++--
 clang/lib/Parse/ParseDeclCXX.cpp  |  4 +++-
 clang/test/Sema/attr-assume.c     | 17 +++++++++++++++++
 4 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index fa191c7378dba4..c6877b61fa7f1e 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -4144,7 +4144,7 @@ def OMPDeclareVariant : InheritableAttr {
 }
 
 def Assumption : InheritableAttr {
-  let Spellings = [Clang<"assume">];
+  let Spellings = [Clang<"assume">, CXX11<"omp", "assume">];
   let Subjects = SubjectList<[Function, ObjCMethod]>;
   let InheritEvenIfAlreadyPresent = 1;
   let Documentation = [AssumptionDocs];
diff --git a/clang/lib/Basic/Attributes.cpp b/clang/lib/Basic/Attributes.cpp
index 44a4f1890d39e1..867d241a2cf847 100644
--- a/clang/lib/Basic/Attributes.cpp
+++ b/clang/lib/Basic/Attributes.cpp
@@ -47,8 +47,12 @@ int clang::hasAttribute(AttributeCommonInfo::Syntax Syntax,
   // attributes. We support those, but not through the typical attribute
   // machinery that goes through TableGen. We support this in all OpenMP modes
   // so long as double square brackets are enabled.
-  if (LangOpts.OpenMP && ScopeName == "omp")
-    return (Name == "directive" || Name == "sequence") ? 1 : 0;
+  //
+  // Other OpenMP attributes (e.g. [[omp::assume]]) are handled via the
+  // regular attribute parsing machinery.
+  if (LangOpts.OpenMP && ScopeName == "omp" &&
+      (Name == "directive" || Name == "sequence"))
+    return 1;
 
   int res = hasAttributeImpl(Syntax, Name, ScopeName, Target, LangOpts);
   if (res)
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 62632b2d79792e..64129d7eaface5 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -4579,7 +4579,9 @@ bool Parser::ParseCXX11AttributeArgs(
     return true;
   }
 
-  if (ScopeName && ScopeName->isStr("omp")) {
+  // [[omp::directive]] and [[omp::sequence]] need special handling.
+  if (ScopeName && ScopeName->isStr("omp") &&
+      (AttrName->isStr("directive") || AttrName->isStr("sequence"))) {
     Diag(AttrNameLoc, getLangOpts().OpenMP >= 51
                           ? diag::warn_omp51_compat_attributes
                           : diag::ext_omp_attributes);
diff --git a/clang/test/Sema/attr-assume.c b/clang/test/Sema/attr-assume.c
index 98deffa3a74609..3b7721647dee60 100644
--- a/clang/test/Sema/attr-assume.c
+++ b/clang/test/Sema/attr-assume.c
@@ -1,5 +1,7 @@
 // RUN: %clang_cc1 -triple i386-apple-darwin9 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -x c++ -fsyntax-only -fopenmp -DCXX -verify %s
 
+#ifndef CXX
 void f1(void) __attribute__((assume(3))); // expected-error {{expected string literal as argument of 'assume' attribute}}
 void f2(void) __attribute__((assume(int))); // expected-error {{expected string literal as argument of 'assume' attribute}}
 void f3(void) __attribute__((assume(for))); // expected-error {{expected string literal as argument of 'assume' attribute}}
@@ -12,3 +14,18 @@ void f9(void) __attribute__((assume("omp_no_openmp", "omp_no_openmp"))); // expe
 
 int g1 __attribute__((assume(0))); // expected-error {{expected string literal as argument of 'assume' attribute}}
 int g2 __attribute__((assume("omp_no_openmp"))); // expected-warning {{'assume' attribute only applies to functions and Objective-C methods}}
+
+#else
+[[omp::assume(3)]] void f1(); // expected-error {{expected string literal as argument of 'assume' attribute}}
+[[omp::assume(int)]] void f2(); // expected-error {{expected string literal as argument of 'assume' attribute}}
+[[omp::assume(for)]] void f3(); // expected-error {{expected string literal as argument of 'assume' attribute}}
+[[omp::assume("QQQQ")]] void f4(); // expected-warning {{unknown assumption string 'QQQQ'; attribute is potentially ignored}}
+[[omp::assume("omp_no_openmp")]] void f5();
+[[omp::assume("omp_noopenmp")]] void f6(); // expected-warning {{unknown assumption string 'omp_noopenmp' may be misspelled; attribute is potentially ignored, did you mean 'omp_no_openmp'?}}
+[[omp::assume("omp_no_openmp_routine")]] void f7(); // expected-warning {{unknown assumption string 'omp_no_openmp_routine' may be misspelled; attribute is potentially ignored, did you mean 'omp_no_openmp_routines'?}}
+[[omp::assume("omp_no_openmp1")]] void f8(); // expected-warning {{unknown assumption string 'omp_no_openmp1' may be misspelled; attribute is potentially ignored, did you mean 'omp_no_openmp'?}}
+[[omp::assume("omp_no_openmp", "omp_no_openmp")]] void f9(); // expected-error {{'assume' attribute takes one argument}}
+
+[[omp::assume(3)]] int g1; // expected-error {{expected string literal as argument of 'assume' attribute}}
+[[omp::assume("omp_no_openmp")]] int g2; // expected-warning {{'assume' attribute only applies to functions and Objective-C methods}}
+#endif