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| author | Joseph Huber <huberjn@outlook.com> | 2024-07-09 07:51:51 -0500 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2024-07-09 07:51:51 -0500 |
| commit | 221d5c570c2ad0201d808b889280ef71b80c1845 (patch) | |
| tree | 5379c891fafa1713d6b40c816ab87838fc741d34 | |
| parent | 2cba218ca573f5da6ff301df59aa686d2e3e40c5 (diff) | |
| download | llvm-221d5c570c2ad0201d808b889280ef71b80c1845.zip llvm-221d5c570c2ad0201d808b889280ef71b80c1845.tar.gz llvm-221d5c570c2ad0201d808b889280ef71b80c1845.tar.bz2 | |
[libc] Disable `-ffreestanding` and `-fno-builtin` on the GPU build (#97636)
Summary:
This patch removed the `-ffreestanding` and `-fno-builtin` flags from
the publically installed version of the GPU library. The presense of
`-fno-builtin` caused issues that prevented all inlining in the GPU C
library, see
https://discourse.llvm.org/t/rfc-libc-ffreestanding-fno-builtin/75883.
Previously, I attempted to fix this by loosening the restriction that
`"no-builtins"` functions cannot be inlined into functions without that
attribute. However, that opened up a lot of extra issues that stalled
that approach.
This patch instead removes that and instead passes `-fno-builtin-<xyz>`
for the few calls that are known to be problematic. I believe this works
in general as the GPU backends do not emit any libcalls and the
implementations of most of these simply reduce to builtins right now.
This is a very useful patch as we can now actually inline calls.
| -rw-r--r-- | libc/cmake/modules/LLVMLibCCompileOptionRules.cmake | 20 |
1 files changed, 17 insertions, 3 deletions
diff --git a/libc/cmake/modules/LLVMLibCCompileOptionRules.cmake b/libc/cmake/modules/LLVMLibCCompileOptionRules.cmake index 58813f5..c5e7dfe 100644 --- a/libc/cmake/modules/LLVMLibCCompileOptionRules.cmake +++ b/libc/cmake/modules/LLVMLibCCompileOptionRules.cmake @@ -43,9 +43,11 @@ function(_get_common_compile_options output_var flags) list(APPEND compile_options "-fpie") if(LLVM_LIBC_FULL_BUILD) + # Only add -ffreestanding flag in non-GPU full build mode. + if(NOT LIBC_TARGET_OS_IS_GPU) + list(APPEND compile_options "-ffreestanding") + endif() list(APPEND compile_options "-DLIBC_FULL_BUILD") - # Only add -ffreestanding flag in full build mode. - list(APPEND compile_options "-ffreestanding") # Manually disable standard include paths to prevent system headers from # being included. if(LIBC_CC_SUPPORTS_NOSTDLIBINC) @@ -68,7 +70,19 @@ function(_get_common_compile_options output_var flags) list(APPEND compile_options "-ffixed-point") endif() - list(APPEND compile_options "-fno-builtin") + # Builtin recognition causes issues when trying to implement the builtin + # functions themselves. The GPU backends do not use libcalls so we disable + # the known problematic ones. This allows inlining during LTO linking. + if(LIBC_TARGET_OS_IS_GPU) + set(libc_builtins bcmp strlen memmem bzero memcmp memcpy memmem memmove + memset strcmp strstr) + foreach(builtin ${libc_builtins}) + list(APPEND compile_options "-fno-builtin-${builtin}") + endforeach() + else() + list(APPEND compile_options "-fno-builtin") + endif() + list(APPEND compile_options "-fno-exceptions") list(APPEND compile_options "-fno-lax-vector-conversions") list(APPEND compile_options "-fno-unwind-tables") |