[PATCH] D138862: [Clang] Do not set offload kind in a freestanding build

[Joseph Huber via Phabricator via cfe-commits]

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The "new" driver embeds metadata along with the compiled device image to
be used by the linking phase. One bit of metadata is the "kind" field
which determines which runtime to generate registration code for once
it's linked. E.g. if it was compiled with OpenMP it should be registered
with the OpenMP runtime.

However, in a freestanding build the implication is that there may not
be a standard runtime and instead we should expect it to be handled
externally. This patch causes the `-ffreestanding` option to set the
value to `None` which results in no registration code being created.

This is useful for generating pure GPU libraries using the offloading
tools. E.g. we can build a `libc` with OpenMP tooling and link it with
`CUDA` without requiring the OpenMP runtime be linked.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D138862

Files:
  clang/lib/Driver/ToolChains/Clang.cpp
  clang/test/Driver/openmp-offload.c


Index: clang/test/Driver/openmp-offload.c
===================================================================
--- clang/test/Driver/openmp-offload.c
+++ clang/test/Driver/openmp-offload.c
@@ -206,3 +206,13 @@
 // RUN:     -fsyntax-only %s 2>&1 | FileCheck -check-prefix=CHK-SYNTAX-ONLY-ARGS %s
 // CHK-SYNTAX-ONLY-ARGS: "-cc1" "-triple" "powerpc64le-ibm-linux-gnu"{{.*}}"-fsyntax-only"
 // CHK-SYNTAX-ONLY-ARGS: "-cc1" "-triple" "powerpc64le-unknown-linux"{{.*}}"-fsyntax-only"
+
+//
+// Ensure that we do not set the kind in a freestanding offloading build.
+//
+// RUN:   %clang -### --target=powerpc64le-linux -fopenmp=libomp -fopenmp-targets=powerpc64le-ibm-linux-gnu \
+// RUN:     -ffreestanding %s 2>&1 | FileCheck -check-prefix=FREESTANDING %s
+// RUN:   %clang -### --target=powerpc64le-linux -fopenmp=libomp -fopenmp-targets=powerpc64le-ibm-linux-gnu \
+// RUN:     -Xopenmp-target=powerpc64le-ibm-linux-gnu -ffreestanding %s 2>&1 | FileCheck -check-prefix=FREESTANDING %s
+// FREESTANDING: "-cc1" "-triple" "powerpc64le-ibm-linux-gnu" "-aux-triple" "powerpc64le-unknown-linux"{{.*}}"-ffreestanding"
+// FREESTANDING: clang-offload-packager"{{.*}}"--image=file={{.*}},triple=powerpc64le-ibm-linux-gnu,arch=,kind=none"
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -8354,8 +8354,10 @@
     StringRef Arch = (OffloadAction->getOffloadingArch())
                          ? OffloadAction->getOffloadingArch()
                          : TCArgs.getLastArgValue(options::OPT_march_EQ);
-    StringRef Kind =
-      Action::GetOffloadKindName(OffloadAction->getOffloadingDeviceKind());
+    StringRef Kind = TCArgs.hasArg(options::OPT_ffreestanding)
+                         ? "none"
+                         : Action::GetOffloadKindName(
+                               OffloadAction->getOffloadingDeviceKind());
 
     ArgStringList Features;
     SmallVector<StringRef> FeatureArgs;


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