Make feature macro undefs conditional on -cl-ext input (intel#426)

Commits d6563b0, de262c9 and d5a2638 have provided a resolution for
`opencl-c-base.h` defining OCL C 3.0 feature macros unconditionally, which
interfered with Compute Runtime's platform-dependent definitions of extension
lists.

An issue with this approach is that `opencl-c-base.h` provides additional
defines based on `__opencl_c_atomic_scope_all_devices` being set:
```
  memory_scope_all_svm_devices = __OPENCL_MEMORY_SCOPE_ALL_SVM_DEVICES,
  memory_scope_all_devices = memory_scope_all_svm_devices,
```
(from https://github.com/llvm/llvm-project/blob/release/16.x/clang/lib/Headers/opencl-c-base.h#L387-L392)

Simply erasing the macro definition from `opencl-c-base.h` leads to memory
scope values' erasure, as the command line definitions aren't available at that
moment due to headers' inclusion order. Original commit d6563b0 did mention an
alternative approach, which accounts for the above issue:
> Once https://reviews.llvm.org/D141297 (LLVM 16) is integrated,
  an alternative approach could be to pass `-D__undef_<feature_macro>`
  <...> at the OCL Clang's level (upon detecting the lack of
  extension-defining inputs to `-cl-ext`).

Implement just that in scope of the current commit. Said LLORG patch simply
needs to be applied for CClang 14-15 instead of the original "unconditional
undef" one.

Signed-off-by: Artem Gindinson <artem.gindinson@intel.com>

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 <sven.vanhaastregt@arm.com>
+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