Make feature macro undefs conditional on -cl-ext input

options_compile.cpp

@@ -20,6 +20,7 @@ Copyright (c) Intel Corporation (2009-2017).
 #include "options.h"
 
 #include "clang/Driver/Options.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/Option/Arg.h"
 #include "llvm/Option/ArgList.h"
 #include "llvm/Support/ManagedStatic.h"
@@ -277,11 +278,30 @@ std::string EffectiveOptionsFilter::processOptions(const OpenCLArgList &args,
         it->second = enabled;
     }
   };
+  llvm::SmallSet<llvm::StringRef, 32> parsedOclCFeatures;
   std::for_each(effectiveArgs.begin(), effectiveArgs.end(),
                 [&](const ArgsVector::value_type &a) {
                   if (a.find("-cl-ext=") == 0)
                     parseClExt(a);
+		  else if (a.find("-D__opencl_c_") == 0)
+		    parsedOclCFeatures.insert(a);
                 });
+
+  // "opencl-c-base.h" unconditionally enables a list of so-called "optional
+  // core" language features. We need to undef those that aren't explicitly
+  // defined within the compilation command (which would suggest that the
+  // target platform supports the corresponding feature).
+  const char* optionalCoreOclCFeaturesList[] = {
+      "__opencl_c_work_group_collective_functions",
+      "__opencl_c_atomic_order_seq_cst",
+      "__opencl_c_atomic_scope_device",
+      "__opencl_c_atomic_scope_all_devices",
+      "__opencl_c_read_write_images" };
+  for (std::string OclCFeature : optionalCoreOclCFeaturesList) {
+    if (!parsedOclCFeatures.contains(std::string("-D") + OclCFeature))
+      effectiveArgs.push_back(std::string("-D__undef_") + OclCFeature);
+  }
+
   // extension is enabled in PCH but disabled or not specifed in options =>
   // disable pch
   bool useModules =

patches/clang/0004-OpenCL-Allow-undefining-header-only-macros.patch

@@ -0,0 +1,104 @@
+From a60b8f468119065f8a6cb4a16598263cb00de0b5 Mon Sep 17 00:00:00 2001
+From: Sven van Haastregt <[email protected]>
+Date: Mon, 16 Jan 2023 11:32:12 +0000
+Subject: [PATCH] [OpenCL] Allow undefining header-only features
+
+`opencl-c-base.h` always defines 5 particular feature macros for
+SPIR-V, making it impossible to disable those features.
+
+To allow disabling any of those features, let the header recognize
+`__undef_<feature>` macros.  The user can then pass the
+`-D__undef_<feature>` flag on the command line to disable a specific
+feature.  The __undef macro could potentially also be set from
+`-cl-ext=-feature`, but for now only change the header and only
+provide __undef macros for the 5 features that are always enabled in
+`opencl-c-base.h`.
+
+Differential Revision: https://reviews.llvm.org/D141297
+---
+ clang/lib/Headers/opencl-c-base.h | 19 ++++++++++++++++
+ clang/test/SemaOpenCL/features.cl | 37 ++++++++++++++++++++++---------
+ 2 files changed, 45 insertions(+), 11 deletions(-)
+
+diff --git a/clang/lib/Headers/opencl-c-base.h b/clang/lib/Headers/opencl-c-base.h
+index c433b4f7eb1af..fad2f9c0272bf 100644
+--- a/clang/lib/Headers/opencl-c-base.h
++++ b/clang/lib/Headers/opencl-c-base.h
+@@ -74,6 +74,25 @@
+ #define __opencl_c_atomic_scope_all_devices 1
+ #define __opencl_c_read_write_images 1
+ #endif // defined(__SPIR__)
++
++// Undefine any feature macros that have been explicitly disabled using
++// an __undef_<feature> macro.
++#ifdef __undef___opencl_c_work_group_collective_functions
++#undef __opencl_c_work_group_collective_functions
++#endif
++#ifdef __undef___opencl_c_atomic_order_seq_cst
++#undef __opencl_c_atomic_order_seq_cst
++#endif
++#ifdef __undef___opencl_c_atomic_scope_device
++#undef __opencl_c_atomic_scope_device
++#endif
++#ifdef __undef___opencl_c_atomic_scope_all_devices
++#undef __opencl_c_atomic_scope_all_devices
++#endif
++#ifdef __undef___opencl_c_read_write_images
++#undef __opencl_c_read_write_images
++#endif
++
+ #endif // (__OPENCL_CPP_VERSION__ == 202100 || __OPENCL_C_VERSION__ == 300)
+
+ #if !defined(__opencl_c_generic_address_space)
+diff --git a/clang/test/SemaOpenCL/features.cl b/clang/test/SemaOpenCL/features.cl
+index af058b5e69828..3f59b4ea3b5ae 100644
+--- a/clang/test/SemaOpenCL/features.cl
++++ b/clang/test/SemaOpenCL/features.cl
+@@ -26,6 +26,15 @@
+ // RUN: %clang_cc1 -triple spir-unknown-unknown %s -E -dM -o - -x cl -cl-std=clc++1.0 \
+ // RUN:   | FileCheck -match-full-lines %s  --check-prefix=NO-FEATURES
+
++// For OpenCL C 3.0, header-only features can be disabled using macros.
++// RUN: %clang_cc1 -triple spir-unknown-unknown %s -E -dM -o - -x cl -cl-std=CL3.0 -fdeclare-opencl-builtins -finclude-default-header \
++// RUN:    -D__undef___opencl_c_work_group_collective_functions=1 \
++// RUN:    -D__undef___opencl_c_atomic_order_seq_cst=1 \
++// RUN:    -D__undef___opencl_c_atomic_scope_device=1 \
++// RUN:    -D__undef___opencl_c_atomic_scope_all_devices=1 \
++// RUN:    -D__undef___opencl_c_read_write_images=1 \
++// RUN:   | FileCheck %s --check-prefix=NO-HEADERONLY-FEATURES
++
+ // Note that __opencl_c_int64 is always defined assuming
+ // always compiling for FULL OpenCL profile
+
+@@ -43,14 +52,20 @@
+ // FEATURES: #define __opencl_c_subgroups 1
+
+ // NO-FEATURES: #define __opencl_c_int64 1
+-// NO-FEATURES-NOT: __opencl_c_3d_image_writes
+-// NO-FEATURES-NOT: __opencl_c_atomic_order_acq_rel
+-// NO-FEATURES-NOT: __opencl_c_atomic_order_seq_cst
+-// NO-FEATURES-NOT: __opencl_c_device_enqueue
+-// NO-FEATURES-NOT: __opencl_c_fp64
+-// NO-FEATURES-NOT: __opencl_c_generic_address_space
+-// NO-FEATURES-NOT: __opencl_c_images
+-// NO-FEATURES-NOT: __opencl_c_pipes
+-// NO-FEATURES-NOT: __opencl_c_program_scope_global_variables
+-// NO-FEATURES-NOT: __opencl_c_read_write_images
+-// NO-FEATURES-NOT: __opencl_c_subgroups
++// NO-FEATURES-NOT: #define __opencl_c_3d_image_writes
++// NO-FEATURES-NOT: #define __opencl_c_atomic_order_acq_rel
++// NO-FEATURES-NOT: #define __opencl_c_atomic_order_seq_cst
++// NO-FEATURES-NOT: #define __opencl_c_device_enqueue
++// NO-FEATURES-NOT: #define __opencl_c_fp64
++// NO-FEATURES-NOT: #define __opencl_c_generic_address_space
++// NO-FEATURES-NOT: #define __opencl_c_images
++// NO-FEATURES-NOT: #define __opencl_c_pipes
++// NO-FEATURES-NOT: #define __opencl_c_program_scope_global_variables
++// NO-FEATURES-NOT: #define __opencl_c_read_write_images
++// NO-FEATURES-NOT: #define __opencl_c_subgroups
++
++// NO-HEADERONLY-FEATURES-NOT: #define __opencl_c_work_group_collective_functions
++// NO-HEADERONLY-FEATURES-NOT: #define __opencl_c_atomic_order_seq_cst
++// NO-HEADERONLY-FEATURES-NOT: #define __opencl_c_atomic_scope_device
++// NO-HEADERONLY-FEATURES-NOT: #define __opencl_c_atomic_scope_all_devices
++// NO-HEADERONLY-FEATURES-NOT: #define __opencl_c_read_write_images