[Mesa-dev] [PATCH] mapi: fix LTO compilation

[Mike Lothian]

This doesn't seem to affect me using GCC 6.1 and gold

On Thu, 2 Jun 2016, 6:42 p.m. Jan Ziak (⚛), <0xe2.0x9a.0x9b at gmail.com>
wrote:

> LTO compilation can sometimes fail with GCC 4.9 and GCC 5.3 because
> src/mapi uses unusual mixing of C code and assembly code. The issue
> may be present in case of GCC 6.1 as well.
>
> This is a Mesa bug rather than a compiler bug (although in an ideal
> world the compilation with -flto should fail if and only if normal
> compilation fails).
>
> The error message:
>
> entry_x86-64_tls.h:61: undefined reference to `x86_64_entry_start'
>
> Without the patch:
> - using "-flto -O2 -DDEBUG" fails with GCC 4.9 and 5.3
> - using "-flto -O3 -DDEBUG" succeeds with GCC 4.9 and 5.3
> - using "-flto -O2 -DNDEBUG" succeeds with GCC 4.9 and 5.3
>
> The patch assumes that the assembler understands ".hidden" directive.
>
> Signed-off-by: Jan Ziak (⚛) <0xe2.0x9a.0x9b at gmail.com>
> ---
>  src/mapi/entry_x86-64_tls.h |  5 +++--
>  src/mapi/entry_x86_tls.h    | 12 +++++++++---
>  2 files changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/src/mapi/entry_x86-64_tls.h b/src/mapi/entry_x86-64_tls.h
> index 38faccc..acabecc 100644
> --- a/src/mapi/entry_x86-64_tls.h
> +++ b/src/mapi/entry_x86-64_tls.h
> @@ -28,6 +28,8 @@
>
>  __asm__(".text\n"
>          ".balign 32\n"
> +        ".globl x86_64_entry_start\n"
> +        ".hidden x86_64_entry_start\n"
>          "x86_64_entry_start:");
>
>  #define STUB_ASM_ENTRY(func)                             \
> @@ -54,8 +56,7 @@ entry_patch_public(void)
>  {
>  }
>
> -static char
> -x86_64_entry_start[];
> +extern char x86_64_entry_start[];
>
>  mapi_func
>  entry_get_public(int slot)
> diff --git a/src/mapi/entry_x86_tls.h b/src/mapi/entry_x86_tls.h
> index 46d2ece..6078b9a 100644
> --- a/src/mapi/entry_x86_tls.h
> +++ b/src/mapi/entry_x86_tls.h
> @@ -29,7 +29,9 @@
>
>  __asm__(".text");
>
> -__asm__("x86_current_tls:\n\t"
> +__asm__( ".globl x86_current_tls\n"
> +       ".hidden x86_current_tls\n"
> +       "x86_current_tls:\n\t"
>         "call 1f\n"
>          "1:\n\t"
>          "popl %eax\n\t"
> @@ -42,6 +44,8 @@ __asm__(".section wtext, \"awx\", @progbits");
>  #endif /* GLX_X86_READONLY_TEXT */
>
>  __asm__(".balign 16\n"
> +        ".globl x86_entry_start\n"
> +        ".hidden x86_entry_start\n"
>          "x86_entry_start:");
>
>  #define STUB_ASM_ENTRY(func)     \
> @@ -60,6 +64,8 @@ __asm__(".balign 16\n"
>
>  #ifndef GLX_X86_READONLY_TEXT
>  __asm__(".balign 16\n"
> +        ".globl x86_entry_end\n"
> +        ".hidden x86_entry_end\n"
>          "x86_entry_end:");
>  __asm__(".text");
>  #endif /* GLX_X86_READONLY_TEXT */
> @@ -71,8 +77,8 @@ __asm__(".text");
>  extern unsigned long
>  x86_current_tls();
>
> -static char x86_entry_start[];
> -static char x86_entry_end[];
> +extern char x86_entry_start[];
> +extern char x86_entry_end[];
>
>  void
>  entry_patch_public(void)
> --
> 2.8.3
>
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> mesa-dev at lists.freedesktop.org
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>
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