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[libc][setjmp] remove naked fn attr #112443

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[libc][setjmp] remove naked fn attr #112443

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6e36ed8
[libc][setjmp] remove naked fn attr
nickdesaulniers Oct 15, 2024
2dc9c1e
reformat
nickdesaulniers Oct 15, 2024
b18649a
avoid clobber
nickdesaulniers Oct 15, 2024
e00688a
early clobber
nickdesaulniers Oct 15, 2024
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12 changes: 0 additions & 12 deletions libc/src/setjmp/setjmp_impl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -17,18 +17,6 @@

namespace LIBC_NAMESPACE_DECL {

// TODO(https://github.com/llvm/llvm-project/issues/112427)
// Some of the architecture-specific definitions are marked `naked`, which in
// GCC implies `nothrow`.
//
// Right now, our aliases aren't marked `nothrow`, so we wind up in a situation
// where clang will emit -Wmissing-exception-spec if we add `nothrow` here, but
// GCC will emit -Wmissing-attributes here without `nothrow`. We need to update
// LLVM_LIBC_FUNCTION to denote when a function throws or not.

#ifdef LIBC_COMPILER_IS_GCC
[[gnu::nothrow]]
#endif
int setjmp(jmp_buf buf);

} // namespace LIBC_NAMESPACE_DECL
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1 change: 1 addition & 0 deletions libc/src/setjmp/x86_64/CMakeLists.txt
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Expand Up @@ -8,6 +8,7 @@ add_entrypoint_object(
libc.hdr.types.jmp_buf
COMPILE_OPTIONS
-O3
-fomit-frame-pointer
)

add_entrypoint_object(
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41 changes: 19 additions & 22 deletions libc/src/setjmp/x86_64/setjmp.cpp
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Expand Up @@ -6,7 +6,6 @@
//
//===----------------------------------------------------------------------===//

#include "include/llvm-libc-macros/offsetof-macro.h"
#include "src/__support/common.h"
#include "src/__support/macros/config.h"
#include "src/setjmp/setjmp_impl.h"
Expand All @@ -17,29 +16,27 @@

namespace LIBC_NAMESPACE_DECL {

[[gnu::naked]]
LLVM_LIBC_FUNCTION(int, setjmp, (jmp_buf buf)) {
long tmp;
asm(R"(
mov %%rbx, %c[rbx](%%rdi)
mov %%rbp, %c[rbp](%%rdi)
mov %%r12, %c[r12](%%rdi)
mov %%r13, %c[r13](%%rdi)
mov %%r14, %c[r14](%%rdi)
mov %%r15, %c[r15](%%rdi)

lea 8(%%rsp), %%rax
mov %%rax, %c[rsp](%%rdi)

mov (%%rsp), %%rax
mov %%rax, %c[rip](%%rdi)

xorl %%eax, %%eax
retq)" ::[rbx] "i"(offsetof(__jmp_buf, rbx)),
[rbp] "i"(offsetof(__jmp_buf, rbp)), [r12] "i"(offsetof(__jmp_buf, r12)),
[r13] "i"(offsetof(__jmp_buf, r13)), [r14] "i"(offsetof(__jmp_buf, r14)),
[r15] "i"(offsetof(__jmp_buf, r15)), [rsp] "i"(offsetof(__jmp_buf, rsp)),
[rip] "i"(offsetof(__jmp_buf, rip))
: "rax");
mov %%rbx, %[rbx]
mov %%rbp, %[rbp]
mov %%r12, %[r12]
mov %%r13, %[r13]
mov %%r14, %[r14]
mov %%r15, %[r15]

lea 8(%%rsp), %[tmp]
mov %[tmp], %[rsp]

mov (%%rsp), %[tmp]
mov %[tmp], %[rip]
)"
: [tmp] "=&r"(tmp)
: [rbx] "m"(buf->rbx), [rbp] "m"(buf->rbp), [r12] "m"(buf->r12),
[r13] "m"(buf->r13), [r14] "m"(buf->r14), [r15] "m"(buf->r15),
[rsp] "m"(buf->rsp), [rip] "m"(buf->rip));
return 0;
}

} // namespace LIBC_NAMESPACE_DECL
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