[Mesa-dev] [RFC] [PATCH] util: Remove check_os_katmai_support.

[Keith Whitwell]

I think this is fine.  It's been a very long time since we had to worry
about this.

Keith

On Mon, 2010-08-16 at 01:17 -0700, Vinson Lee wrote:
> I am proposing to remove the check_os_katmai_support function from u_cpu_detect.
> 
> util: Remove check_os_katmai_support.
> 
> check_os_katmai_support checks that the operating system running on a SSE-capable processor supports SSE. This is necessary for unpatched 2.2.x and earlier kernels. 2.4.x and later kernels support SSE.
> 
> check_os_katmai_support will disable SSE capabilities for 32-bit x86 operating systems for which there is no code path. Currently, this function handles Linux, Windows, and several BSDs. Mac OS, Cygwin, and Solaris are several operating systems with no code paths.
> 
> Rather than add code for the unhandled operating systems, remove this function altogether. This will fix SSE detection on all recent 32-bit x86 operating systems. This completely breaks functionality on unpatched 2.2.x and earlier kernels, although there are likely no Gallium3D users on such operating systems.
> 
> 
> diff --git a/src/gallium/auxiliary/util/u_cpu_detect.c b/src/gallium/auxiliary/util/u_cpu_detect.c
> index 5056351..b9b9f92 100644
> --- a/src/gallium/auxiliary/util/u_cpu_detect.c
> +++ b/src/gallium/auxiliary/util/u_cpu_detect.c
> @@ -194,123 +194,8 @@ check_os_altivec_support(void)
>  }
>  #endif /* PIPE_ARCH_PPC */
>  
> -/* If we're running on a processor that can do SSE, let's see if we
> - * are allowed to or not.  This will catch 2.4.0 or later kernels that
> - * haven't been configured for a Pentium III but are running on one,
> - * and RedHat patched 2.2 kernels that have broken exception handling
> - * support for user space apps that do SSE.
> - */
> -#if defined(PIPE_ARCH_X86) || defined (PIPE_ARCH_X86_64)
> -static void
> -check_os_katmai_support(void)
> -{
> -#if defined(PIPE_ARCH_X86)
> -#if defined(PIPE_OS_FREEBSD)
> -   int has_sse=0, ret;
> -   int len = sizeof (has_sse);
> -
> -   ret = sysctlbyname("hw.instruction_sse", &has_sse, &len, NULL, 0);
> -   if (ret || !has_sse)
> -      util_cpu_caps.has_sse=0;
> -
> -#elif defined(PIPE_OS_NETBSD) || defined(PIPE_OS_OPENBSD)
> -   int has_sse, has_sse2, ret, mib[2];
> -   int varlen;
> -
> -   mib[0] = CTL_MACHDEP;
> -   mib[1] = CPU_SSE;
> -   varlen = sizeof (has_sse);
> -
> -   ret = sysctl(mib, 2, &has_sse, &varlen, NULL, 0);
> -   if (ret < 0 || !has_sse) {
> -      util_cpu_caps.has_sse = 0;
> -   } else {
> -      util_cpu_caps.has_sse = 1;
> -   }
> -
> -   mib[1] = CPU_SSE2;
> -   varlen = sizeof (has_sse2);
> -   ret = sysctl(mib, 2, &has_sse2, &varlen, NULL, 0);
> -   if (ret < 0 || !has_sse2) {
> -      util_cpu_caps.has_sse2 = 0;
> -   } else {
> -      util_cpu_caps.has_sse2 = 1;
> -   }
> -   util_cpu_caps.has_sse = 0; /* FIXME ?!?!? */
> -
> -
> -#elif defined(PIPE_OS_WINDOWS)
> -   LPTOP_LEVEL_EXCEPTION_FILTER exc_fil;
> -   if (util_cpu_caps.has_sse) {
> -      exc_fil = SetUnhandledExceptionFilter(win32_sig_handler_sse);
> -#if defined(PIPE_CC_GCC)
> -      __asm __volatile ("xorps %xmm0, %xmm0");
> -#elif defined(PIPE_CC_MSVC)
> -      __asm {
> -          xorps xmm0, xmm0        /* executing SSE instruction */
> -      }
> -#else
> -#error Unsupported compiler
> -#endif
> -      SetUnhandledExceptionFilter(exc_fil);
> -   }
> -#elif defined(PIPE_OS_LINUX)
> -   struct sigaction saved_sigill;
> -   struct sigaction saved_sigfpe;
> -
> -   /* Save the original signal handlers.
> -   */
> -   sigaction(SIGILL, NULL, &saved_sigill);
> -   sigaction(SIGFPE, NULL, &saved_sigfpe);
> -
> -   signal(SIGILL, (void (*)(int))sigill_handler_sse);
> -   signal(SIGFPE, (void (*)(int))sigfpe_handler_sse);
> -
> -   /* Emulate test for OSFXSR in CR4.  The OS will set this bit if it
> -    * supports the extended FPU save and restore required for SSE.  If
> -    * we execute an SSE instruction on a PIII and get a SIGILL, the OS
> -    * doesn't support Streaming SIMD Exceptions, even if the processor
> -    * does.
> -    */
> -   if (util_cpu_caps.has_sse) {
> -      __asm __volatile ("xorps %xmm1, %xmm0");
> -   }
> -
> -   /* Emulate test for OSXMMEXCPT in CR4.  The OS will set this bit if
> -    * it supports unmasked SIMD FPU exceptions.  If we unmask the
> -    * exceptions, do a SIMD divide-by-zero and get a SIGILL, the OS
> -    * doesn't support unmasked SIMD FPU exceptions.  If we get a SIGFPE
> -    * as expected, we're okay but we need to clean up after it.
> -    *
> -    * Are we being too stringent in our requirement that the OS support
> -    * unmasked exceptions?  Certain RedHat 2.2 kernels enable SSE by
> -    * setting CR4.OSFXSR but don't support unmasked exceptions.  Win98
> -    * doesn't even support them.  We at least know the user-space SSE
> -    * support is good in kernels that do support unmasked exceptions,
> -    * and therefore to be safe I'm going to leave this test in here.
> -    */
> -   if (util_cpu_caps.has_sse) {
> -      /* test_os_katmai_exception_support(); */
> -   }
> -
> -   /* Restore the original signal handlers.
> -   */
> -   sigaction(SIGILL, &saved_sigill, NULL);
> -   sigaction(SIGFPE, &saved_sigfpe, NULL);
> -
> -#else
> -   /* We can't use POSIX signal handling to test the availability of
> -    * SSE, so we disable it by default.
> -    */
> -   util_cpu_caps.has_sse = 0;
> -#endif /* __linux__ */
> -#endif
> -
> -#if defined(PIPE_ARCH_X86_64)
> -   util_cpu_caps.has_sse = 1;
> -#endif
> -}
> -
>  
> +#if defined(PIPE_ARCH_X86) || defined (PIPE_ARCH_X86_64)
>  static int has_cpuid(void)
>  {
>  #if defined(PIPE_ARCH_X86)
> @@ -469,9 +354,6 @@ util_cpu_detect(void)
>           util_cpu_caps.cacheline = regs2[2] & 0xFF;
>        }
>  
> -      if (util_cpu_caps.has_sse)
> -         check_os_katmai_support();
> -
>        if (!util_cpu_caps.has_sse) {
>           util_cpu_caps.has_sse2 = 0;
>           util_cpu_caps.has_sse3 = 0;