e0b4a7063f
When compiler-rt is built for a GPU target in the same runtimes build
as LLVM-libc, the profile sources `#include <string.h>`, `<limits.h>`,
... Those headers are generated by LLVM-libc for the GPU triple.
A concrete example is the amdgcn runtimes build:
-DLLVM_RUNTIME_TARGETS='default;amdgcn-amd-amdhsa'
-DRUNTIMES_amdgcn-amd-amdhsa_LLVM_ENABLE_RUNTIMES='compiler-rt;libc'
-DRUNTIMES_amdgcn-amd-amdhsa_RUNTIMES_USE_LIBC=llvm-libc
Even though `libc` is configured before `compiler-rt`, both sets of
targets live in the same ninja graph and race each other. Ninja can
start compiling `compiler-rt/lib/profile/InstrProfiling.c` before
LLVM-libc has finished generating its GPU `string.h`, and even when
hdrgen has finished, the profile compile needs `-isystem` pointing at
the generated header tree.
Use the runtimes-side libc-provider abstraction in
`runtimes/cmake/Modules/HandleLibC.cmake`:
- at compiler-rt top level, `include(HandleLibC)` when
`LLVM_RUNTIMES_BUILD` is set, so all compiler-rt subcomponents can
reuse the `runtimes-libc-*` targets. `libcxx` / `libcxxabi` /
`libunwind` include it the same way at their top-level CMakeLists.
- in `compiler-rt/lib/profile/CMakeLists.txt`, when the GPU build
sees the sibling `runtimes-libc-headers` target, pass it through
`LINK_LIBS` of `add_compiler_rt_runtime(clang_rt.profile ...)`.
In the `llvm-libc` case this pulls in LLVM-libc's `libc-headers`
(`-isystem <build>/include/<triple>`), waits for
`generate-libc-headers`, and adds `-nostdlibinc` so the profile compile
does not consult host C library paths.
The dependency is added only when `COMPILER_RT_GPU_BUILD` is on and the
sibling `runtimes-libc-headers` target actually exists, so host
compiler-rt builds, standalone compiler-rt builds, and runtimes builds
without LLVM-libc selected are unchanged.
`add_compiler_rt_runtime` passes `LINK_LIBS` to
`target_link_libraries(<libname> PRIVATE ...)`, so the include path is
used when compiling the profile target itself but is not propagated to
downstream consumers of `libclang_rt.profile.a`.
Related: PR #177665.
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40 KiB