[clang] [Clang][SYCL] Introduce clang-sycl-linker to link SYCL offloading device code (Part 1 of many) (PR #112245)

[Alexey Bader via cfe-commits]

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+// Tests the clang-sycl-linker tool.
+//
+// Test a simple case without arguments.
+// RUN: %clangxx -fsycl -emit-llvm -c %s -o %t.bc
+// RUN: clang-sycl-linker --dry-run -triple spirv64 %t.bc -o a.spv 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=SIMPLE
+// SIMPLE: "{{.*}}llvm-link{{.*}}" {{.*}}.bc -o [[FIRSTLLVMLINKOUT:.*]].bc --suppress-warnings
+// SIMPLE-NEXT: "{{.*}}llvm-spirv{{.*}}" {{.*}}-o a.spv [[FIRSTLLVMLINKOUT]].bc
+//
+// Test a simple case with device library files specified.
+// RUN: echo ' ' > %T/lib1.bc
+// RUN: echo ' ' > %T/lib2.bc
+// RUN: clang-sycl-linker --dry-run -triple spirv64 %t.bc --library-path=%T --device-libs=lib1.bc,lib2.bc -o a.spv 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=DEVLIBS
+// DEVLIBS: "{{.*}}llvm-link{{.*}}" {{.*}}.bc -o [[FIRSTLLVMLINKOUT:.*]].bc --suppress-warnings
+// DEVLIBS-NEXT: "{{.*}}llvm-link{{.*}}" -only-needed [[FIRSTLLVMLINKOUT]].bc {{.*}}lib1.bc {{.*}}lib2.bc -o [[SECONDLLVMLINKOUT:.*]].bc --suppress-warnings
+// DEVLIBS-NEXT: "{{.*}}llvm-spirv{{.*}}" {{.*}}-o a.spv [[SECONDLLVMLINKOUT]].bc
+//
+// Test a simple case with .o (fat object) as input.
+// TODO: Remove this test once fat object support is added.
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bader wrote:

Is `clang-sycl-linker` supposed to support fat objects? According to my understanding, this tool links the device code only. Some other tool (e.g. `clang-linker-wrapper`) is supposed to extract device code from fat objects and invoke `clang-sycl-linker` tool to link the device code. I think this tool is supposed to handle object files, but only 'lean'. @jhuber6, did I get it right?

https://github.com/llvm/llvm-project/pull/112245